[Intel-gfx] [PATCH v2] drm/i915: Clamp min_cdclk to max_cdclk_freq to unblock 8K

[Jani Nikula]

On Thu, 02 Jul 2020, Manasi Navare <manasi.d.navare at intel.com> wrote:
> On Thu, Jul 02, 2020 at 12:15:26PM +0300, Stanislav Lisovskiy wrote:
>> We still need "Bump up CDCLK" workaround otherwise getting
>> underruns - however currently it blocks 8K as CDCLK = Pixel rate,
>> in 8K case would require CDCLK to be around 1 Ghz which is not
>> possible.
>> 
>> v2: - Convert to expression(max(min_cdclk, min(pixel_rate, max_cdclk))
>>       (Ville Syrjälä)
>>     - Use type specific min_t, max_t(Ville Syrjälä)
>> 
>> Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
>
> I have tested this and this unblocks 8K 
>
> Reviewed-by: Manasi Navare <manasi.d.navare at intel.com>

Thanks for the patch and review, pushed to dinq.

BR,
Jani.

>
> Manasi
>
>> ---
>>  drivers/gpu/drm/i915/display/intel_cdclk.c | 11 +++++++++--
>>  1 file changed, 9 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
>> index 45f7f33d1144..8f9320e1e249 100644
>> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
>> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
>> @@ -2080,8 +2080,15 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
>>  	 * Explicitly stating here that this seems to be currently
>>  	 * rather a Hack, than final solution.
>>  	 */
>> -	if (IS_TIGERLAKE(dev_priv))
>> -		min_cdclk = max(min_cdclk, (int)crtc_state->pixel_rate);
>> +	if (IS_TIGERLAKE(dev_priv)) {
>> +		/*
>> +		 * Clamp to max_cdclk_freq in case pixel rate is higher,
>> +		 * in order not to break an 8K, but still leave W/A at place.
>> +		 */
>> +		min_cdclk = max_t(int, min_cdclk,
>> +				  min_t(int, crtc_state->pixel_rate,
>> +					dev_priv->max_cdclk_freq));
>> +	}
>>  
>>  	if (min_cdclk > dev_priv->max_cdclk_freq) {
>>  		drm_dbg_kms(&dev_priv->drm,
>> -- 
>> 2.24.1.485.gad05a3d8e5
>> 
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-- 
Jani Nikula, Intel Open Source Graphics Center