Re: [PATCH v2] drm/i915: Add fallback for CDCLK selection when min_cdclk is too high

["Naladala, Ramanaidu" <Ramanaidu.naladala@intel.com>]

Hi Mika,

Thanks for the review.

On 10/28/2025 5:37 PM, Kahola, Mika wrote:
>> -----Original Message-----
>> From: Intel-xe <intel-xe-bounces@lists.freedesktop.org> On Behalf Of Naladala Ramanaidu
>> Sent: Friday, 17 October 2025 18.05
>> To: intel-xe@lists.freedesktop.org; intel-gfx@lists.freedesktop.org
>> Cc: ville.syrjala@linux.intel.com; Nautiyal, Ankit K <ankit.k.nautiyal@intel.com>; Naladala, Ramanaidu
>> <ramanaidu.naladala@intel.com>
>> Subject: [PATCH v2] drm/i915: Add fallback for CDCLK selection when min_cdclk is too high
>>
>> In cases where the requested minimum CDCLK exceeds all available values for the current reference clock, the CDCLK selection
>> logic previously returned 0. This could result coverity division or modulo by zero issue.
>>
>> This change introduces a fallback mechanism that returns the platform's max_cdclk_freq instead of 0.
>>
>> v2: Update safe fallback value to max cdclk.
>>
>> Fixes: Coverity CID 2628056
> We shouldn't mention the static analysis error ids as most of the audience cannot trace it back.
>
> With this change, this is
Sure. I will remove this Fixes tag while merging the patch.
>
> Reviewed-by: Mika Kahola <mika.kahola@intel.com>
>
>> Signed-off-by: Naladala Ramanaidu <ramanaidu.naladala@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_cdclk.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
>> index e92e7fd9fd13..da97c38cca14 100644
>> --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
>> +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
>> @@ -1561,7 +1561,7 @@ static int bxt_calc_cdclk(struct intel_display *display, int min_cdclk)
>>   	drm_WARN(display->drm, 1,
>>   		 "Cannot satisfy minimum cdclk %d with refclk %u\n",
>>   		 min_cdclk, display->cdclk.hw.ref);
>> -	return 0;
>> +	return display->cdclk.max_cdclk_freq;
>>   }
>>
>>   static int bxt_calc_cdclk_pll_vco(struct intel_display *display, int cdclk)
>> --
>> 2.43.0