[Intel-gfx] [PATCH 14/14] drm/i915: Add two-stage ILK-style watermark programming (v4)

[Maarten Lankhorst]

Op 17-09-15 om 15:05 schreef Ville Syrjälä:
> On Thu, Sep 17, 2015 at 02:38:12PM +0200, Maarten Lankhorst wrote:
>> Hey,
>>
>> It's worh nothing this series may have a soft dependency on Ville's cleanups,
>> because else pixel_rate == 0 during boot. :(
>>
>> This patch breaks when the initial sprite watermarks are set on ironlake, but no sprite is enabled.
>>
>> A naive fix is below, without it my laptop won't power the screen because intermediate wm calculation fails. :(
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index 41a4dbaf600b..bf874ff97024 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -2457,7 +2457,7 @@ static int ilk_compute_intermediate_wm(struct drm_device *dev,
>>  
>>  		a_wm->enable &= b_wm->enable;
>>  		a_wm->pri_val = max(a_wm->pri_val, b_wm->pri_val);
>> -		a_wm->spr_val = max(a_wm->spr_val, b_wm->spr_val);
>> +		a_wm->spr_val = a->sprites_enabled ? max(a_wm->spr_val, b_wm->spr_val) : 0;
>>  		a_wm->cur_val = max(a_wm->cur_val, b_wm->cur_val);
>>  		a_wm->fbc_val = max(a_wm->fbc_val, b_wm->fbc_val);
>>  	}
> Hmm. That could work, but feels a bit wrong. Would be nice if we could
> always keep the watermarks totally consistent with the plane
> configuration.
>
> One thing we could do during init is simply calculate the optimal
> watermarks for the current config and just blast them in. Then when
> the first plane update/modeset happens the current state would
> actually be sane wrt. the current plane config.
>
That would work too, as long as we end up with something sane I'm all for it. :-)