From: Jani Nikula <jani.nikula@intel.com>
To: imre.deak@intel.com
Cc: intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, Ankit
 Nautiyal <ankit.k.nautiyal@intel.com>, stable@vger.kernel.org
Subject: Re: [PATCH 01/14] drm/i915/dp: Iterate DSC BPP from high to low on
 all platforms
In-Reply-To: <Z5zQ9BjEkA_PN9Ns@ideak-desk.fi.intel.com>
Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
References: <cover.1738327620.git.jani.nikula@intel.com>
 <3bba67923cbcd13a59d26ef5fa4bb042b13c8a9b.1738327620.git.jani.nikula@intel.com>
 <Z5zQ9BjEkA_PN9Ns@ideak-desk.fi.intel.com>
Date: Mon, 03 Feb 2025 16:46:28 +0200
Message-ID: <87ikpr6q7v.fsf@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain

On Fri, 31 Jan 2025, Imre Deak <imre.deak@intel.com> wrote:
> On Fri, Jan 31, 2025 at 02:49:54PM +0200, Jani Nikula wrote:
>> Commit 1c56e9a39833 ("drm/i915/dp: Get optimal link config to have best
>> compressed bpp") tries to find the best compressed bpp for the
>> link. However, it iterates from max to min bpp on display 13+, and from
>> min to max on other platforms. This presumably leads to minimum
>> compressed bpp always being chosen on display 11-12.
>> 
>> Iterate from high to low on all platforms to actually use the best
>> possible compressed bpp.
>> 
>> Fixes: 1c56e9a39833 ("drm/i915/dp: Get optimal link config to have best compressed bpp")
>> Cc: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> Cc: Imre Deak <imre.deak@intel.com>
>> Cc: <stable@vger.kernel.org> # v6.7+
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>
> Reviewed-by: Imre Deak <imre.deak@intel.com>

Thanks for the swift reviews! Pushed the lot to drm-intel-next.

BR,
Jani.

>
>> ---
>>  drivers/gpu/drm/i915/display/intel_dp.c | 7 +++----
>>  1 file changed, 3 insertions(+), 4 deletions(-)
>> 
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index d1b4fd542a1f..ecf192262eb9 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -2073,11 +2073,10 @@ icl_dsc_compute_link_config(struct intel_dp *intel_dp,
>>  	/* Compressed BPP should be less than the Input DSC bpp */
>>  	dsc_max_bpp = min(dsc_max_bpp, output_bpp - 1);
>>  
>> -	for (i = 0; i < ARRAY_SIZE(valid_dsc_bpp); i++) {
>> -		if (valid_dsc_bpp[i] < dsc_min_bpp)
>> +	for (i = ARRAY_SIZE(valid_dsc_bpp) - 1; i >= 0; i--) {
>> +		if (valid_dsc_bpp[i] < dsc_min_bpp ||
>> +		    valid_dsc_bpp[i] > dsc_max_bpp)
>>  			continue;
>> -		if (valid_dsc_bpp[i] > dsc_max_bpp)
>> -			break;
>>  
>>  		ret = dsc_compute_link_config(intel_dp,
>>  					      pipe_config,
>> -- 
>> 2.39.5
>> 

-- 
Jani Nikula, Intel