Re: [PATCH] drm/i915: disable CPU PWM also on LPT/SPT backlight disable

From: Jani Nikula
Date: Thu Oct 08 2015 - 09:40:51 EST



Huang, please try this patch.

BR,
Jani.


On Tue, 29 Sep 2015, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
> Also adding Cc: intel-gfx, please include that in follow-ups.
>
> Thanks,
> Jani.
>
> On Tue, 29 Sep 2015, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
>> Although we don't support or enable CPU PWM with LPT/SPT based systems,
>> it may have been enabled prior to loading the driver. Disable the CPU
>> PWM on LPT/SPT backlight disable to avoid warnings on LCPLL disable.
>>
>> The issue has been present on BDW since BDW enabling, but was recently
>> introduced on HSW with
>>
>> commit 437b15b8017e0d946453c10794b0c5d4591cf180
>> Author: Jani Nikula <jani.nikula@xxxxxxxxx>
>> Date: Fri Sep 4 16:55:13 2015 +0300
>>
>> drm/i915: use pch backlight override on hsw too
>>
>> Reference: http://mid.gmane.org/87y4frhwsn.fsf@xxxxxxxxxxxxxxxxxxxx
>> Reported-by: kernel test robot <ying.huang@xxxxxxxxx>
>> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/intel_panel.c | 14 ++++++++++++++
>> 1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
>> index dd71e7f139e3..c9c94d05f3dd 100644
>> --- a/drivers/gpu/drm/i915/intel_panel.c
>> +++ b/drivers/gpu/drm/i915/intel_panel.c
>> @@ -731,6 +731,20 @@ static void lpt_disable_backlight(struct intel_connector *connector)
>>
>> intel_panel_actually_set_backlight(connector, 0);
>>
>> + /*
>> + * Although we don't support or enable CPU PWM with LPT/SPT based
>> + * systems, it may have been enabled prior to loading the
>> + * driver. Disable to avoid warnings on LCPLL disable.
>> + *
>> + * This needs rework if we need to add support for CPU PWM on PCH split
>> + * platforms.
>> + */
>> + tmp = I915_READ(BLC_PWM_CPU_CTL2);
>> + if (tmp & BLM_PWM_ENABLE) {
>> + DRM_DEBUG_KMS("cpu backlight was enabled, disabling\n");
>> + I915_WRITE(BLC_PWM_CPU_CTL2, tmp & ~BLM_PWM_ENABLE);
>> + }
>> +
>> tmp = I915_READ(BLC_PWM_PCH_CTL1);
>> I915_WRITE(BLC_PWM_PCH_CTL1, tmp & ~BLM_PCH_PWM_ENABLE);
>> }
>> --
>> 2.1.4
>>
>
> --
> Jani Nikula, Intel Open Source Technology Center

--
Jani Nikula, Intel Open Source Technology Center
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