Re: [PATCH 4/4] drm/i915: fix link rates reported for SKL

[Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>]

On 8/17/2015 6:11 PM, Ville Syrjälä wrote:
> On Mon, Aug 17, 2015 at 05:45:11PM +0530, Sivakumar Thulasimani wrote:
>> From: "Thulasimani,Sivakumar" <sivakumar.thulasimani@intel.com>
>>
>> This patch fixes the bug that SKL SKUs before B0 might return
>> HBR2 as supported even though it is not supposed to be enabled
>> on such platforms.
>>
>> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_dp.c |   14 ++++++++------
>>   1 file changed, 8 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>> index 03523b3..963fdae 100644
>> --- a/drivers/gpu/drm/i915/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>> @@ -1224,21 +1224,23 @@ static bool intel_dp_is_hbr2_supported(struct drm_device *dev)
>>   static int
>>   intel_dp_source_rates(struct drm_device *dev, const int **source_rates)
>>   {
>> +	int size = 0;
>>   	if (IS_BROXTON(dev)) {
>>   		*source_rates = bxt_rates;
>> -		return ARRAY_SIZE(bxt_rates);
>> +		size = ARRAY_SIZE(bxt_rates);
>>   	} else if (IS_SKYLAKE(dev)) {
>>   		*source_rates = skl_rates;
>> -		return ARRAY_SIZE(skl_rates);
>> +		size = ARRAY_SIZE(skl_rates);
>> +	} else {
>> +		*source_rates = default_rates;
>> +		size = ARRAY_SIZE(default_rates);
>>   	}
>>   
>> -	*source_rates = default_rates;
>> -
>>   	/* This depends on the fact that 5.4 is last value in the array */
>>   	if (intel_dp_is_hbr2_supported(dev))
>> -		return (DP_LINK_BW_5_4 >> 3) + 1;
>> +		return size;
>>   	else
>> -		return (DP_LINK_BW_2_7 >> 3) + 1;
>> +		return size - 1;
> Maybe we should use rate_to_index() here? Should be a bit more
> future proof for when we get HBR3. So, perhaps something like this?
>
> {
> 	...
> 		*source_rates = bxt_rates;
> 		size_rates = ARRAY_SIZE(bxt_rates);
> 	...
>
> 	if (intel_dp_is_hbr2_supported)
> 		max_rate = 540000;
> 	else
> 		max_rate = 270000;
>
> 	size = rate_to_index(max_rate, *source_rates) + 1;
> 	if (WARN_ON(size > size_rates))
> 		size = size_rates;
>
> 	return size;
> }
>
> But that could be a followup patch.
>
> Otherwise the series looks good so:
> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
thanks for the review :)
>>   }
>>   
>>   static void
>> -- 
>> 1.7.9.5

-- 
regards,
Sivakumar

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