The DSDTs on most Cherry Trail devices have an ugly clutch where the PWM controller gets poked from the _PS0 method of the graphics-card device:
Local0 = PSAT /* _SB_.PCI0.GFX0.PSAT */ If (((Local0 & 0x03) == 0x03)) { PSAT &= 0xFFFFFFFC Local1 = PSAT /* _SB_.PCI0.GFX0.PSAT */ RSTA = Zero RSTF = Zero RSTA = One RSTF = One PWMB |= 0xC0000000 PWMC = PWMB /* _SB_.PCI0.GFX0.PWMB */ }
Where PSAT is the power-status register of the PWM controller, so if it is in D3 when the GFX0 device's PS0 method runs then it will turn it on and restore the PWM ctrl register value it saved from its PS3 handler. Note not only does it restore it, it ors it with 0xC0000000 turning it on at a time where we may not want it to get turned on at all.
The pwm_get call which the i915 driver does to get a reference to the PWM controller, already adds a device-link making the GFX0 device a consumer of the PWM device. So it should already have been resumed when the above AML runs and the AML should thus not do its undesirable poking of the PWM controller register.
But the PCI core powers on PCI devices in the no-irq resume phase and thus calls the troublesome PS0 method in the no-irq resume phase. Where as LPSS devices by default are resumed in the early resume phase.
This commit sets the resume_from_noirq flag in the bsw_pwm_dev_desc struct, so that Cherry Trail PWM controllers will be resumed in the no-irq phase. Together with the device-link added by the pwm-get this ensures that the PWM controller will be on when the troublesome PS0 method runs, which stops it from poking the PWM controller.
Acked-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Hans de Goede hdegoede@redhat.com --- drivers/acpi/acpi_lpss.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c index 5e2bfbcf526f..67892fc0b822 100644 --- a/drivers/acpi/acpi_lpss.c +++ b/drivers/acpi/acpi_lpss.c @@ -257,6 +257,7 @@ static const struct lpss_device_desc bsw_pwm_dev_desc = { .flags = LPSS_SAVE_CTX | LPSS_NO_D3_DELAY, .prv_offset = 0x800, .setup = bsw_pwm_setup, + .resume_from_noirq = true, };
static const struct lpss_device_desc byt_uart_dev_desc = {