The DSDTs on most Cherry Trail devices have an ugly clutch where the PWM controller gets turned off from the _PS3 method of the graphics-card dev:

Method (_PS3, 0, Serialized) // _PS3: Power State 3 { ... PWMB = PWMC /* _SB_.PCI0.GFX0.PWMC */ PSAT |= 0x03 Local0 = PSAT /* _SB_.PCI0.GFX0.PSAT */ ... }

Where PSAT is the power-status register of the PWM controller.

Since the i915 driver will do a pwm_get on the pwm device as it uses it to control the LCD panel backlight, there is a device-link marking the i915 device as a consumer of the pwm device. So that the PWM controller will always be suspended after the i915 driver suspends (which is the right thing to do). This causes the above GFX0 PS3 AML code to run before acpi_lpss.c calls acpi_lpss_save_ctx().

So on these devices the PWM controller will already be off when acpi_lpss_save_ctx() runs. This causes it to read/save all 1-s (0xffffffff) as ctx register values.

When these bogus values get restored on resume the PWM controller actually keeps working, since most bits are reserved, but this does set bit 3 of the LPSS General purpose register, which for the PWM controller has the following function: "This bit is re-used to support 32kHz slow mode. Default is 19.2MHz as PWM source clock".

This causes the clock of the PWM controller to switch from 19.2MHz to 32KHz, which is a slow-down of a factor 600. Surprisingly enough so far there have been few bug reports about this. This is likely because the i915 driver was hardcoding the PWM frequency to 46 KHz, which divided by 600 would result in a PWM frequency of approx. 78 Hz, which mostly still works fine. There are some bug reports about the LCD backlight flickering after suspend/resume which are likely caused by this issue.

But with the upcoming patch-series to finally switch the i915 drivers code for external PWM controllers to use the atomic API and to honor the PWM frequency specified in the video BIOS (VBT), this becomes a much bigger problem. On most cases the VBT specifies either 200 Hz or 20 KHz as PWM frequency, which with the mentioned issue ends up being either 1/3 Hz, where the backlight actually visible blinks on and off every 3s, or in 33 Hz and horrible flickering of the backlight.

There are a number of possible solutions to this problem:

1. Make acpi_lpss_save_ctx() run before GFX0._PS3 Pro: Clean solution from pov of not medling with save/restore ctx code Con: As mentioned the current ordering is the right thing to do Con: Requires assymmetry in at what suspend/resume phase we do the save vs restore, requiring more suspend/resume ordering hacks in already convoluted acpi_lpss.c suspend/resume code. 2. Do some sort of save once mode for the LPSS ctx Pro: Reasonably clean Con: Needs a new LPSS flag + code changes to handle the flag 3. Detect we have failed to save the ctx registers and do not restore them Pro: Not PWM specific, might help with issues on other LPSS devices too Con: If we can get away with not restoring the ctx why bother with it at all? 4. Do not save the ctx for CHT PWM controllers Pro: Clean, as simple as dropping a flag? Con: Not so simple as dropping a flag, needs a new flag to ensure that we still do lpss_deassert_reset() on device activation. 5. Make the pwm-lpss code fixup the LPSS-context registers Pro: Keeps acpi_lpss.c code clean Con: Moves knowledge of LPSS-context into the pwm-lpss.c code

1 and 5 both do not seem to be a desirable way forward.

3 and 4 seem ok, but they both assume that restoring the LPSS-context registers is not necessary. I have done a couple of test and those do show that restoring the LPSS-context indeed does not seem to be necessary on devices using s2idle suspend (and successfully reaching S0i3). But I have no hardware to test deep / S3 suspend. So I'm not sure that not restoring the context is safe.

That leaves solution 2, which is about as simple / clean as 3 and 4, so this commit fixes the described problem by implementing a new LPSS_SAVE_CTX_ONCE flag and setting that for the CHT PWM controllers.

Acked-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v2: - Move #define LPSS_SAVE_CTX_ONCE define to group it with LPSS_SAVE_CTX --- drivers/acpi/acpi_lpss.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c index 67892fc0b822..a8d7d83ac761 100644 --- a/drivers/acpi/acpi_lpss.c +++ b/drivers/acpi/acpi_lpss.c @@ -67,7 +67,15 @@ ACPI_MODULE_NAME("acpi_lpss"); #define LPSS_CLK_DIVIDER BIT(2) #define LPSS_LTR BIT(3) #define LPSS_SAVE_CTX BIT(4) -#define LPSS_NO_D3_DELAY BIT(5) +/* + * For some devices the DSDT AML code for another device turns off the device + * before our suspend handler runs, causing us to read/save all 1-s (0xffffffff) + * as ctx register values. + * Luckily these devices always use the same ctx register values, so we can + * work around this by saving the ctx registers once on activation. + */ +#define LPSS_SAVE_CTX_ONCE BIT(5) +#define LPSS_NO_D3_DELAY BIT(6)

struct lpss_private_data;

@@ -254,7 +262,7 @@ static const struct lpss_device_desc byt_pwm_dev_desc = { };

static const struct lpss_device_desc bsw_pwm_dev_desc = { - .flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY, + .flags = LPSS_SAVE_CTX_ONCE | LPSS_NO_D3_DELAY, .prv_offset = 0x800, .setup = bsw_pwm_setup, .resume_from_noirq = true, @@ -885,9 +893,14 @@ static int acpi_lpss_activate(struct device *dev) * we have to deassert reset line to be sure that ->probe() will * recognize the device. */ - if (pdata->dev_desc->flags & LPSS_SAVE_CTX) + if (pdata->dev_desc->flags & (LPSS_SAVE_CTX | LPSS_SAVE_CTX_ONCE)) lpss_deassert_reset(pdata);

+#ifdef CONFIG_PM + if (pdata->dev_desc->flags & LPSS_SAVE_CTX_ONCE) + acpi_lpss_save_ctx(dev, pdata); +#endif + return 0; }

@@ -1031,7 +1044,7 @@ static int acpi_lpss_resume(struct device *dev)

acpi_lpss_d3_to_d0_delay(pdata);

- if (pdata->dev_desc->flags & LPSS_SAVE_CTX) + if (pdata->dev_desc->flags & (LPSS_SAVE_CTX | LPSS_SAVE_CTX_ONCE)) acpi_lpss_restore_ctx(dev, pdata);

return 0;

When the user requests a high enough period ns value, then the calculations in pwm_lpss_prepare() might result in a base_unit value of 0.

But according to the data-sheet the way the PWM controller works is that each input clock-cycle the base_unit gets added to a N bit counter and that counter overflowing determines the PWM output frequency. Adding 0 to the counter is a no-op. The data-sheet even explicitly states that writing 0 to the base_unit bits will result in the PWM outputting a continuous 0 signal.

When the user requestes a low enough period ns value, then the calculations in pwm_lpss_prepare() might result in a base_unit value which is bigger then base_unit_range - 1. Currently the codes for this deals with this by applying a mask:

base_unit &= (base_unit_range - 1);

But this means that we let the value overflow the range, we throw away the higher bits and store whatever value is left in the lower bits into the register leading to a random output frequency, rather then clamping the output frequency to the highest frequency which the hardware can do.

This commit fixes both issues by clamping the base_unit value to be between 1 and (base_unit_range - 1).

Fixes: 684309e5043e ("pwm: lpss: Avoid potential overflow of base_unit") Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v5: - Use clamp_val(... instead of clam_t(unsigned long long, ...

Changes in v3: - Change upper limit of clamp to (base_unit_range - 1) - Add Fixes tag --- drivers/pwm/pwm-lpss.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 43b1fc634af1..da9bc3d10104 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -97,6 +97,8 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, freq *= base_unit_range;

base_unit = DIV_ROUND_CLOSEST_ULL(freq, c); + /* base_unit must not be 0 and we also want to avoid overflowing it */ + base_unit = clamp_val(base_unit, 1, base_unit_range - 1);

on_time_div = 255ULL * duty_ns; do_div(on_time_div, period_ns); @@ -105,7 +107,6 @@ static void pwm_lpss_prepare(struct pwm_lpss_chip *lpwm, struct pwm_device *pwm, orig_ctrl = ctrl = pwm_lpss_read(pwm); ctrl &= ~PWM_ON_TIME_DIV_MASK; ctrl &= ~((base_unit_range - 1) << PWM_BASE_UNIT_SHIFT); - base_unit &= (base_unit_range - 1); ctrl |= (u32) base_unit << PWM_BASE_UNIT_SHIFT; ctrl |= on_time_div;

Before this commit a suspend + resume of the LPSS PWM controller would result in the controller being reset to its defaults of output-freq = clock/256, duty-cycle=100%, until someone changes to the output-freq and/or duty-cycle are made.

This problem has been masked so far because the main consumer (the i915 driver) was always making duty-cycle changes on resume. With the conversion of the i915 driver to the atomic PWM API the driver now only disables/enables the PWM on suspend/resume leaving the output-freq and duty as is, triggering this problem.

The LPSS PWM controller has a mechanism where the ctrl register value and the actual base-unit and on-time-div values used are latched. When software sets the SW_UPDATE bit then at the end of the current PWM cycle, the new values from the ctrl-register will be latched into the actual registers, and the SW_UPDATE bit will be cleared.

The problem is that before this commit our suspend/resume handling consisted of simply saving the PWM ctrl register on suspend and restoring it on resume, without setting the PWM_SW_UPDATE bit. When the controller has lost its state over a suspend/resume and thus has been reset to the defaults, just restoring the register is not enough. We must also set the SW_UPDATE bit to tell the controller to latch the restored values into the actual registers.

Fixing this problem is not as simple as just or-ing in the value which is being restored with SW_UPDATE. If the PWM was enabled before we must write the new settings + PWM_SW_UPDATE before setting PWM_ENABLE. We must also wait for PWM_SW_UPDATE to become 0 again and depending on the model we must do this either before or after the setting of PWM_ENABLE.

All the necessary logic for doing this is already present inside pwm_lpss_apply(), so instead of duplicating this inside the resume handler, this commit makes the resume handler use pwm_lpss_apply() to restore the settings when necessary. This fixes the output-freq and duty-cycle being reset to their defaults on resume.

Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v5: - The changes to pwm_lpss_apply() are much cleaner now thanks to the new pwm_lpss_prepare_enable() helper.

Changes in v3: - This replaces the "pwm: lpss: Set SW_UPDATE bit when enabling the PWM" patch from previous versions of this patch-set, which really was a hack working around the resume issue which this patch fixes properly. --- drivers/pwm/pwm-lpss.c | 56 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c index 8a136ba2a583..cf4eaf7ef2a2 100644 --- a/drivers/pwm/pwm-lpss.c +++ b/drivers/pwm/pwm-lpss.c @@ -143,29 +143,39 @@ static int pwm_lpss_prepare_enable(struct pwm_lpss_chip *lpwm, return 0; }

-static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, - const struct pwm_state *state) +static int __pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state, bool from_resume) { struct pwm_lpss_chip *lpwm = to_lpwm(chip); int ret = 0;

if (state->enabled) { if (!pwm_is_enabled(pwm)) { - pm_runtime_get_sync(chip->dev); + if (!from_resume) + pm_runtime_get_sync(chip->dev); + ret = pwm_lpss_prepare_enable(lpwm, pwm, state, true); - if (ret) + if (ret && !from_resume) pm_runtime_put(chip->dev); } else { ret = pwm_lpss_prepare_enable(lpwm, pwm, state, false); } } else if (pwm_is_enabled(pwm)) { pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE); - pm_runtime_put(chip->dev); + + if (!from_resume) + pm_runtime_put(chip->dev); }

return ret; }

+static int pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + return __pwm_lpss_apply(chip, pwm, state, false); +} + static void pwm_lpss_get_state(struct pwm_chip *chip, struct pwm_device *pwm, struct pwm_state *state) { @@ -278,10 +288,40 @@ EXPORT_SYMBOL_GPL(pwm_lpss_suspend); int pwm_lpss_resume(struct device *dev) { struct pwm_lpss_chip *lpwm = dev_get_drvdata(dev); - int i; + struct pwm_state saved_state; + struct pwm_device *pwm; + int i, ret; + u32 ctrl;

- for (i = 0; i < lpwm->info->npwm; i++) - writel(lpwm->saved_ctrl[i], lpwm->regs + i * PWM_SIZE + PWM); + for (i = 0; i < lpwm->info->npwm; i++) { + pwm = &lpwm->chip.pwms[i]; + + ctrl = pwm_lpss_read(pwm); + /* If we did not reach S0i3/S3 the controller keeps its state */ + if (ctrl == lpwm->saved_ctrl[i]) + continue; + + /* + * We cannot just blindly restore the old value here. Since we + * are changing the settings we must set SW_UPDATE and if the + * PWM was enabled before we must write the new settings + + * PWM_SW_UPDATE before setting PWM_ENABLE. We must also wait + * for PWM_SW_UPDATE to become 0 again and depending on the + * model we must do this either before or after the setting of + * PWM_ENABLE. + * So instead of reproducing all the code from pwm_apply() here, + * we just reapply the state as stored in pwm->state. + */ + saved_state = pwm->state; + /* + * Update enabled to its actual setting for the + * enabled<->disabled transitions inside apply(). + */ + pwm->state.enabled = !!(ctrl & PWM_ENABLE); + ret = __pwm_lpss_apply(&lpwm->chip, pwm, &saved_state, true); + if (ret) + dev_err(dev, "Error restoring state on resume\n"); + }

return 0; }

While looking into adding atomic-pwm support to the pwm-crc driver I noticed something odd, there is a PWM_BASE_CLK define of 6 MHz and there is a clock-divider which divides this with a value between 1-128, and there are 256 duty-cycle steps.

The pwm-crc code before this commit assumed that a clock-divider setting of 1 means that the PWM output is running at 6 MHZ, if that is true, where do these 256 duty-cycle steps come from?

This would require an internal frequency of 256 * 6 MHz = 1.5 GHz, that seems unlikely for a PMIC which is using a silicon process optimized for power-switching transistors. It is way more likely that there is an 8 bit counter for the duty cycle which acts as an extra fixed divider wrt the PWM output frequency.

The main user of the pwm-crc driver is the i915 GPU driver which uses it for backlight control. Lets compare the PWM register values set by the video-BIOS (the GOP), assuming the extra fixed divider is present versus the PWM frequency specified in the Video-BIOS-Tables:

Device: PWM Hz set by BIOS PWM Hz specified in VBT Asus T100TA 200 200 Asus T100HA 200 200 Lenovo Miix 2 8 23437 20000 Toshiba WT8-A 23437 20000

So as we can see if we assume the extra division by 256 then the register values set by the GOP are an exact match for the VBT values, where as otherwise the values would be of by a factor of 256.

This commit fixes the period / duty_cycle calculations to take the extra division by 256 into account.

Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v3: - Use NSEC_PER_USEC instead of adding a new (non-sensical) NSEC_PER_MHZ define --- drivers/pwm/pwm-crc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index 272eeb071147..c056eb9b858c 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -21,8 +21,8 @@

#define PWM_MAX_LEVEL 0xFF

-#define PWM_BASE_CLK 6000000 /* 6 MHz */ -#define PWM_MAX_PERIOD_NS 21333 /* 46.875KHz */ +#define PWM_BASE_CLK_MHZ 6 /* 6 MHz */ +#define PWM_MAX_PERIOD_NS 5461333 /* 183 Hz */

/** * struct crystalcove_pwm - Crystal Cove PWM controller @@ -72,7 +72,7 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,

/* changing the clk divisor, need to disable fisrt */ crc_pwm_disable(c, pwm); - clk_div = PWM_BASE_CLK * period_ns / NSEC_PER_SEC; + clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC);

regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, clk_div | PWM_OUTPUT_ENABLE);

The CRC PWM controller has a clock-divider which divides the clock with a value between 1-128. But as can seen from the PWM_DIV_CLK_xxx defines, this range maps to a register value of 0-127.

So after calculating the clock-divider we must subtract 1 to get the register value, unless the requested frequency was so high that the calculation has already resulted in a (rounded) divider value of 0.

Note that before this fix, setting a period of PWM_MAX_PERIOD_NS which corresponds to the max. divider value of 128 could have resulted in a bug where the code would use 128 as divider-register value which would have resulted in an actual divider value of 0 (and the enable bit being set). A rounding error stopped this bug from actually happen. This same rounding error means that after the subtraction of 1 it is impossible to set the divider to 128. Also bump PWM_MAX_PERIOD_NS by 1 ns to allow setting a divider of 128 (register-value 127).

Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v3: - Introduce crc_pwm_calc_clk_div() here instead of later in the patch-set to reduce the amount of churn in the patch-set a bit --- drivers/pwm/pwm-crc.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index c056eb9b858c..44ec7d5b63e1 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -22,7 +22,7 @@ #define PWM_MAX_LEVEL 0xFF

#define PWM_BASE_CLK_MHZ 6 /* 6 MHz */ -#define PWM_MAX_PERIOD_NS 5461333 /* 183 Hz */ +#define PWM_MAX_PERIOD_NS 5461334 /* 183 Hz */

/** * struct crystalcove_pwm - Crystal Cove PWM controller @@ -39,6 +39,18 @@ static inline struct crystalcove_pwm *to_crc_pwm(struct pwm_chip *pc) return container_of(pc, struct crystalcove_pwm, chip); }

+static int crc_pwm_calc_clk_div(int period_ns) +{ + int clk_div; + + clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC); + /* clk_div 1 - 128, maps to register values 0-127 */ + if (clk_div > 0) + clk_div--; + + return clk_div; +} + static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm) { struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); @@ -68,11 +80,10 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm, }

if (pwm_get_period(pwm) != period_ns) { - int clk_div; + int clk_div = crc_pwm_calc_clk_div(period_ns);

/* changing the clk divisor, need to disable fisrt */ crc_pwm_disable(c, pwm); - clk_div = PWM_BASE_CLK_MHZ * period_ns / (256 * NSEC_PER_USEC);

regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, clk_div | PWM_OUTPUT_ENABLE);

The pwm-crc code is using 2 different enable bits: 1. bit 7 of the PWM0_CLK_DIV (PWM_OUTPUT_ENABLE) 2. bit 0 of the BACKLIGHT_EN register

I strongly suspect that the BACKLIGHT_EN register at address 0x51 really controls a separate output-only GPIO which is connected to the LCD panels backlight-enable input. Like how the PANEL_EN register at address 0x52 controls an output-only GPIO which is earmarked for the LCD panel's enable pin. If this is correct then this GPIO should really be added to the gpio-crystalcove.c driver and the PWM driver should stop poking it. But I've been unable to come up with a definitive answer here, so I'm keeping this as is for now.

As the comment in the old code already indicates we must disable the PWM before we can change the clock divider. But the crc_pwm_disable() and crc_pwm_enable() calls the old code make for this only change the BACKLIGHT_EN register; and the value of that register does not matter for changing the period / the divider. What does matter is that the PWM_OUTPUT_ENABLE bit must be cleared before a new value can be written.

This commit modifies crc_pwm_config() to clear PWM_OUTPUT_ENABLE instead when changing the period, so that period changes actually work.

Note this fix will cause a significant behavior change on some devices using the CRC PWM output to drive their backlight. Before the PWM would always run with the output frequency configured by the BIOS at boot, now the period time specified by the i915 driver will actually be honored.

Signed-off-by: Hans de Goede hdegoede@redhat.com --- drivers/pwm/pwm-crc.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index 44ec7d5b63e1..81232da0c767 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -82,14 +82,11 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm, if (pwm_get_period(pwm) != period_ns) { int clk_div = crc_pwm_calc_clk_div(period_ns);

- /* changing the clk divisor, need to disable fisrt */ - crc_pwm_disable(c, pwm); + /* changing the clk divisor, clear PWM_OUTPUT_ENABLE first */ + regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0);

regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, clk_div | PWM_OUTPUT_ENABLE); - - /* enable back */ - crc_pwm_enable(c, pwm); }

/* change the pwm duty cycle */

The pwm-crc code is using 2 different enable bits: 1. bit 7 of the PWM0_CLK_DIV (PWM_OUTPUT_ENABLE) 2. bit 0 of the BACKLIGHT_EN register

So far we've kept the PWM_OUTPUT_ENABLE bit set when disabling the PWM, this commit makes crc_pwm_disable() clear it on disable and makes crc_pwm_enable() set it again on re-enable.

Acked-by: Uwe Kleine-König u.kleine-koenig@pengutronix.de Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v3: - Remove paragraph about tri-stating the output from the commit message, we don't have a datasheet so this was just an unfounded guess --- drivers/pwm/pwm-crc.c | 4 ++++ 1 file changed, 4 insertions(+)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index 81232da0c767..b72008c9b072 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -54,7 +54,9 @@ static int crc_pwm_calc_clk_div(int period_ns) static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm) { struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); + int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));

+ regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div | PWM_OUTPUT_ENABLE); regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1);

return 0; @@ -63,8 +65,10 @@ static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm) static void crc_pwm_disable(struct pwm_chip *c, struct pwm_device *pwm) { struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); + int div = crc_pwm_calc_clk_div(pwm_get_period(pwm));

regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0); + regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div); }

static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,

Replace the enable, disable and config pwm_ops with an apply op, to support the new atomic PWM API.

Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v3: - Keep crc_pwm_calc_clk_div() helper to avoid needless churn --- drivers/pwm/pwm-crc.c | 89 ++++++++++++++++++++++++++----------------- 1 file changed, 53 insertions(+), 36 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index b72008c9b072..8a7f4707279c 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -51,59 +51,76 @@ static int crc_pwm_calc_clk_div(int period_ns) return clk_div; }

-static int crc_pwm_enable(struct pwm_chip *c, struct pwm_device *pwm) +static int crc_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) { - struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); - int div = crc_pwm_calc_clk_div(pwm_get_period(pwm)); - - regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div | PWM_OUTPUT_ENABLE); - regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1); - - return 0; -} - -static void crc_pwm_disable(struct pwm_chip *c, struct pwm_device *pwm) -{ - struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); - int div = crc_pwm_calc_clk_div(pwm_get_period(pwm)); - - regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0); - regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, div); -} - -static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm, - int duty_ns, int period_ns) -{ - struct crystalcove_pwm *crc_pwm = to_crc_pwm(c); + struct crystalcove_pwm *crc_pwm = to_crc_pwm(chip); struct device *dev = crc_pwm->chip.dev; - int level; + int err;

- if (period_ns > PWM_MAX_PERIOD_NS) { + if (state->period > PWM_MAX_PERIOD_NS) { dev_err(dev, "un-supported period_ns\n"); return -EINVAL; }

- if (pwm_get_period(pwm) != period_ns) { - int clk_div = crc_pwm_calc_clk_div(period_ns); + if (state->polarity != PWM_POLARITY_NORMAL) + return -EOPNOTSUPP; + + if (pwm_is_enabled(pwm) && !state->enabled) { + err = regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 0); + if (err) { + dev_err(dev, "Error writing BACKLIGHT_EN %d\n", err); + return err; + } + } + + if (pwm_get_duty_cycle(pwm) != state->duty_cycle || + pwm_get_period(pwm) != state->period) { + int level = state->duty_cycle * PWM_MAX_LEVEL / state->period;

+ err = regmap_write(crc_pwm->regmap, PWM0_DUTY_CYCLE, level); + if (err) { + dev_err(dev, "Error writing PWM0_DUTY_CYCLE %d\n", err); + return err; + } + } + + if (pwm_is_enabled(pwm) && state->enabled && + pwm_get_period(pwm) != state->period) { /* changing the clk divisor, clear PWM_OUTPUT_ENABLE first */ - regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0); + err = regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, 0); + if (err) { + dev_err(dev, "Error writing PWM0_CLK_DIV %d\n", err); + return err; + } + }

- regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, - clk_div | PWM_OUTPUT_ENABLE); + if (pwm_get_period(pwm) != state->period || + pwm_is_enabled(pwm) != state->enabled) { + int clk_div = crc_pwm_calc_clk_div(state->period); + int pwm_output_enable = state->enabled ? PWM_OUTPUT_ENABLE : 0; + + err = regmap_write(crc_pwm->regmap, PWM0_CLK_DIV, + clk_div | pwm_output_enable); + if (err) { + dev_err(dev, "Error writing PWM0_CLK_DIV %d\n", err); + return err; + } }

- /* change the pwm duty cycle */ - level = duty_ns * PWM_MAX_LEVEL / period_ns; - regmap_write(crc_pwm->regmap, PWM0_DUTY_CYCLE, level); + if (!pwm_is_enabled(pwm) && state->enabled) { + err = regmap_write(crc_pwm->regmap, BACKLIGHT_EN, 1); + if (err) { + dev_err(dev, "Error writing BACKLIGHT_EN %d\n", err); + return err; + } + }

return 0; }

static const struct pwm_ops crc_pwm_ops = { - .config = crc_pwm_config, - .enable = crc_pwm_enable, - .disable = crc_pwm_disable, + .apply = crc_pwm_apply, };

static int crystalcove_pwm_probe(struct platform_device *pdev)

Implement the pwm_ops.get_state() method to complete the support for the new atomic PWM API.

Reviewed-by: Andy Shevchenko andriy.shevchenko@linux.intel.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- Changes in v5: - Fix an indentation issue

Changes in v4: - Use DIV_ROUND_UP when calculating the period and duty_cycle from the controller's register values

Changes in v3: - Add Andy's Reviewed-by tag - Remove extra whitespace to align some code after assignments (requested by Uwe Kleine-König) --- drivers/pwm/pwm-crc.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c index 8a7f4707279c..370ab826a20b 100644 --- a/drivers/pwm/pwm-crc.c +++ b/drivers/pwm/pwm-crc.c @@ -119,8 +119,39 @@ static int crc_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, return 0; }

+static void crc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct crystalcove_pwm *crc_pwm = to_crc_pwm(chip); + struct device *dev = crc_pwm->chip.dev; + unsigned int clk_div, clk_div_reg, duty_cycle_reg; + int error; + + error = regmap_read(crc_pwm->regmap, PWM0_CLK_DIV, &clk_div_reg); + if (error) { + dev_err(dev, "Error reading PWM0_CLK_DIV %d\n", error); + return; + } + + error = regmap_read(crc_pwm->regmap, PWM0_DUTY_CYCLE, &duty_cycle_reg); + if (error) { + dev_err(dev, "Error reading PWM0_DUTY_CYCLE %d\n", error); + return; + } + + clk_div = (clk_div_reg & ~PWM_OUTPUT_ENABLE) + 1; + + state->period = + DIV_ROUND_UP(clk_div * NSEC_PER_USEC * 256, PWM_BASE_CLK_MHZ); + state->duty_cycle = + DIV_ROUND_UP(duty_cycle_reg * state->period, PWM_MAX_LEVEL); + state->polarity = PWM_POLARITY_NORMAL; + state->enabled = !!(clk_div_reg & PWM_OUTPUT_ENABLE); +} + static const struct pwm_ops crc_pwm_ops = { .apply = crc_pwm_apply, + .get_state = crc_pwm_get_state, };

static int crystalcove_pwm_probe(struct platform_device *pdev)

So far for devices using an external PWM controller (devices using pwm_setup_backlight()), we have been hardcoding the period-time passed to pwm_config() to 21333 ns.

I suspect this was done because many VBTs set the PWM frequency to 200 which corresponds to a period-time of 5000000 ns, which greatly exceeds the PWM_MAX_PERIOD_NS define in the Crystal Cove PMIC PWM driver, which used to be 21333.

This PWM_MAX_PERIOD_NS define was actually based on a bug in the PWM driver where its period and duty-cycle times where off by a factor of 256.

Due to this bug the hardcoded CRC_PMIC_PWM_PERIOD_NS value of 21333 would result in the PWM driver using its divider of 128, which would result in a PWM output frequency of 6000000 Hz / 256 / 128 = 183 Hz. So actually pretty close to the default VBT value of 200 Hz.

Now that this bug in the pwm-crc driver is fixed, we can actually use the VBT defined frequency.

This is important because:

a) With the pwm-crc driver fixed it will now translate the hardcoded CRC_PMIC_PWM_PERIOD_NS value of 21333 ns / 46 Khz to a PWM output frequency of 23 KHz (the max it can do).

b) The pwm-lpss driver used on many models has always honored the 21333 ns / 46 Khz request

Some panels do not like such high output frequencies. E.g. on a Terra Pad 1061 tablet, using the LPSS PWM controller, the backlight would go from off to max, when changing the sysfs backlight brightness value from 90-100%, anything under aprox. 90% would turn the backlight fully off.

Honoring the VBT specified PWM frequency will also hopefully fix the various bug reports which we have received about users perceiving the backlight to flicker after a suspend/resume cycle.

Acked-by: Jani Nikula jani.nikula@intel.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- .../drm/i915/display/intel_display_types.h | 1 + drivers/gpu/drm/i915/display/intel_panel.c | 19 +++++++++++-------- 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h index 2bf3d4cb4ea9..de32f9efb120 100644 --- a/drivers/gpu/drm/i915/display/intel_display_types.h +++ b/drivers/gpu/drm/i915/display/intel_display_types.h @@ -223,6 +223,7 @@ struct intel_panel { bool util_pin_active_low; /* bxt+ */ u8 controller; /* bxt+ only */ struct pwm_device *pwm; + int pwm_period_ns;

/* DPCD backlight */ u8 pwmgen_bit_count; diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c index 8efdd9f08a08..14e611c92194 100644 --- a/drivers/gpu/drm/i915/display/intel_panel.c +++ b/drivers/gpu/drm/i915/display/intel_panel.c @@ -40,8 +40,6 @@ #include "intel_dsi_dcs_backlight.h" #include "intel_panel.h"

-#define CRC_PMIC_PWM_PERIOD_NS 21333 - void intel_fixed_panel_mode(const struct drm_display_mode *fixed_mode, struct drm_display_mode *adjusted_mode) @@ -597,7 +595,7 @@ static u32 pwm_get_backlight(struct intel_connector *connector) int duty_ns;

duty_ns = pwm_get_duty_cycle(panel->backlight.pwm); - return DIV_ROUND_UP(duty_ns * 100, CRC_PMIC_PWM_PERIOD_NS); + return DIV_ROUND_UP(duty_ns * 100, panel->backlight.pwm_period_ns); }

static void lpt_set_backlight(const struct drm_connector_state *conn_state, u32 level) @@ -671,9 +669,10 @@ static void bxt_set_backlight(const struct drm_connector_state *conn_state, u32 static void pwm_set_backlight(const struct drm_connector_state *conn_state, u32 level) { struct intel_panel *panel = &to_intel_connector(conn_state->connector)->panel; - int duty_ns = DIV_ROUND_UP(level * CRC_PMIC_PWM_PERIOD_NS, 100); + int duty_ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);

- pwm_config(panel->backlight.pwm, duty_ns, CRC_PMIC_PWM_PERIOD_NS); + pwm_config(panel->backlight.pwm, duty_ns, + panel->backlight.pwm_period_ns); }

static void @@ -1917,6 +1916,9 @@ static int pwm_setup_backlight(struct intel_connector *connector, return -ENODEV; }

+ panel->backlight.pwm_period_ns = NSEC_PER_SEC / + get_vbt_pwm_freq(dev_priv); + /* * FIXME: pwm_apply_args() should be removed when switching to * the atomic PWM API. @@ -1926,9 +1928,10 @@ static int pwm_setup_backlight(struct intel_connector *connector, panel->backlight.min = 0; /* 0% */ panel->backlight.max = 100; /* 100% */ level = intel_panel_compute_brightness(connector, 100); - ns = DIV_ROUND_UP(level * CRC_PMIC_PWM_PERIOD_NS, 100); + ns = DIV_ROUND_UP(level * panel->backlight.pwm_period_ns, 100);

- retval = pwm_config(panel->backlight.pwm, ns, CRC_PMIC_PWM_PERIOD_NS); + retval = pwm_config(panel->backlight.pwm, ns, + panel->backlight.pwm_period_ns); if (retval < 0) { drm_err(&dev_priv->drm, "Failed to configure the pwm chip\n"); pwm_put(panel->backlight.pwm); @@ -1937,7 +1940,7 @@ static int pwm_setup_backlight(struct intel_connector *connector, }

level = DIV_ROUND_UP(pwm_get_duty_cycle(panel->backlight.pwm) * 100, - CRC_PMIC_PWM_PERIOD_NS); + panel->backlight.pwm_period_ns); panel->backlight.level = intel_panel_compute_brightness(connector, level); panel->backlight.enabled = panel->backlight.level != 0;