The HSM clock needs to be setup at around 101% of the pixel rate. This was done previously by setting the clock rate to 163.7MHz at probe time and only check in mode_valid whether the mode pixel clock was under the pixel clock +1% or not.
However, with 4k we need to change that frequency to a higher frequency than 163.7MHz, and yet want to have the lowest clock as possible to have a decent power saving.
Let's change that logic a bit by setting the clock rate of the HSM clock to the pixel rate at encoder_enable time. This would work for the BCM2711 that support 4k resolutions and has a clock that can provide it, but we still have to take care of a 4k panel plugged on a BCM283x SoCs that wouldn't be able to use those modes, so let's define the limit in the variant.
Signed-off-by: Maxime Ripard maxime@cerno.tech --- drivers/gpu/drm/vc4/vc4_hdmi.c | 79 ++++++++++++++++------------------- drivers/gpu/drm/vc4/vc4_hdmi.h | 3 +- 2 files changed, 41 insertions(+), 41 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c index 356334eeaf66..df3973acbe88 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.c +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c @@ -52,7 +52,6 @@ #include "vc4_hdmi_regs.h" #include "vc4_regs.h"
-#define HSM_CLOCK_FREQ 163682864 #define CEC_CLOCK_FREQ 40000
static int vc4_hdmi_debugfs_regs(struct seq_file *m, void *unused) @@ -328,6 +327,7 @@ static void vc4_hdmi_encoder_disable(struct drm_encoder *encoder) HDMI_WRITE(HDMI_VID_CTL, HDMI_READ(HDMI_VID_CTL) & ~VC4_HD_VID_CTL_ENABLE);
+ clk_disable_unprepare(vc4_hdmi->hsm_clock); clk_disable_unprepare(vc4_hdmi->pixel_clock);
ret = pm_runtime_put(&vc4_hdmi->pdev->dev); @@ -425,6 +425,7 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder) struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder); struct vc4_hdmi_encoder *vc4_encoder = to_vc4_hdmi_encoder(encoder); bool debug_dump_regs = false; + unsigned long pixel_rate, hsm_rate; int ret;
ret = pm_runtime_get_sync(&vc4_hdmi->pdev->dev); @@ -433,9 +434,8 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder) return; }
- ret = clk_set_rate(vc4_hdmi->pixel_clock, - mode->clock * 1000 * - ((mode->flags & DRM_MODE_FLAG_DBLCLK) ? 2 : 1)); + pixel_rate = mode->clock * 1000 * ((mode->flags & DRM_MODE_FLAG_DBLCLK) ? 2 : 1); + ret = clk_set_rate(vc4_hdmi->pixel_clock, pixel_rate); if (ret) { DRM_ERROR("Failed to set pixel clock rate: %d\n", ret); return; @@ -447,6 +447,36 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder) return; }
+ /* + * As stated in RPi's vc4 firmware "HDMI state machine (HSM) clock must + * be faster than pixel clock, infinitesimally faster, tested in + * simulation. Otherwise, exact value is unimportant for HDMI + * operation." This conflicts with bcm2835's vc4 documentation, which + * states HSM's clock has to be at least 108% of the pixel clock. + * + * Real life tests reveal that vc4's firmware statement holds up, and + * users are able to use pixel clocks closer to HSM's, namely for + * 1920x1200@60Hz. So it was decided to have leave a 1% margin between + * both clocks. Which, for RPi0-3 implies a maximum pixel clock of + * 162MHz. + * + * Additionally, the AXI clock needs to be at least 25% of + * pixel clock, but HSM ends up being the limiting factor. + */ + hsm_rate = max_t(unsigned long, 120000000, (pixel_rate / 100) * 101); + ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate); + if (ret) { + DRM_ERROR("Failed to set HSM clock rate: %d\n", ret); + return; + } + + ret = clk_prepare_enable(vc4_hdmi->hsm_clock); + if (ret) { + DRM_ERROR("Failed to turn on HSM clock: %d\n", ret); + clk_disable_unprepare(vc4_hdmi->pixel_clock); + return; + } + if (vc4_hdmi->variant->reset) vc4_hdmi->variant->reset(vc4_hdmi);
@@ -561,23 +591,9 @@ static enum drm_mode_status vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder, const struct drm_display_mode *mode) { - /* - * As stated in RPi's vc4 firmware "HDMI state machine (HSM) clock must - * be faster than pixel clock, infinitesimally faster, tested in - * simulation. Otherwise, exact value is unimportant for HDMI - * operation." This conflicts with bcm2835's vc4 documentation, which - * states HSM's clock has to be at least 108% of the pixel clock. - * - * Real life tests reveal that vc4's firmware statement holds up, and - * users are able to use pixel clocks closer to HSM's, namely for - * 1920x1200@60Hz. So it was decided to have leave a 1% margin between - * both clocks. Which, for RPi0-3 implies a maximum pixel clock of - * 162MHz. - * - * Additionally, the AXI clock needs to be at least 25% of - * pixel clock, but HSM ends up being the limiting factor. - */ - if (mode->clock > HSM_CLOCK_FREQ / (1000 * 101 / 100)) + struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder); + + if ((mode->clock * 1000) > vc4_hdmi->variant->max_pixel_clock) return MODE_CLOCK_HIGH;
return MODE_OK; @@ -1347,23 +1363,6 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) return -EPROBE_DEFER; }
- /* This is the rate that is set by the firmware. The number - * needs to be a bit higher than the pixel clock rate - * (generally 148.5Mhz). - */ - ret = clk_set_rate(vc4_hdmi->hsm_clock, HSM_CLOCK_FREQ); - if (ret) { - DRM_ERROR("Failed to set HSM clock rate: %d\n", ret); - goto err_put_i2c; - } - - ret = clk_prepare_enable(vc4_hdmi->hsm_clock); - if (ret) { - DRM_ERROR("Failed to turn on HDMI state machine clock: %d\n", - ret); - goto err_put_i2c; - } - /* Only use the GPIO HPD pin if present in the DT, otherwise * we'll use the HDMI core's register. */ @@ -1420,9 +1419,7 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data) err_destroy_encoder: vc4_hdmi_encoder_destroy(encoder); err_unprepare_hsm: - clk_disable_unprepare(vc4_hdmi->hsm_clock); pm_runtime_disable(dev); -err_put_i2c: put_device(&vc4_hdmi->ddc->dev);
return ret; @@ -1445,7 +1442,6 @@ static void vc4_hdmi_unbind(struct device *dev, struct device *master, vc4_hdmi_connector_destroy(&vc4_hdmi->connector); vc4_hdmi_encoder_destroy(&vc4_hdmi->encoder.base.base);
- clk_disable_unprepare(vc4_hdmi->hsm_clock); pm_runtime_disable(dev);
put_device(&vc4_hdmi->ddc->dev); @@ -1470,6 +1466,7 @@ static int vc4_hdmi_dev_remove(struct platform_device *pdev) static const struct vc4_hdmi_variant bcm2835_variant = { .encoder_type = VC4_ENCODER_TYPE_HDMI0, .debugfs_name = "hdmi_regs", + .max_pixel_clock = 162000000, .cec_available = true, .registers = vc4_hdmi_fields, .num_registers = ARRAY_SIZE(vc4_hdmi_fields), diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.h b/drivers/gpu/drm/vc4/vc4_hdmi.h index 20e0f5498f1e..9a6831b941d9 100644 --- a/drivers/gpu/drm/vc4/vc4_hdmi.h +++ b/drivers/gpu/drm/vc4/vc4_hdmi.h @@ -36,6 +36,9 @@ struct vc4_hdmi_variant { /* Set to true when the CEC support is available */ bool cec_available;
+ /* Maximum pixel clock supported by the controller (in Hz) */ + unsigned long long max_pixel_clock; + /* List of the registers available on that variant */ const struct vc4_hdmi_register *registers;