Re: [PATCH v4 2/4] drm: Add aspect ratio parsing in DRM layer

["Sharma, Shashank" <shashank.sharma@intel.com>]

Regards

Shashank


On 10/17/2016 6:01 PM, Ville Syrjälä wrote:
> On Mon, Oct 17, 2016 at 05:34:38PM +0530, Shashank Sharma wrote:
>> Current DRM layer functions don't parse aspect ratio information
>> while converting a user mode->kernel mode or vice versa. This
>> causes modeset to pick mode with wrong aspect ratio, eventually
>> causing failures in HDMI compliance test cases, due to wrong VIC.
>>
>> This patch adds aspect ratio information in DRM's mode conversion
>> and mode comparision functions, to make sure kernel picks mode
>> with right aspect ratio (as per the VIC).
>>
>> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
>> Signed-off-by: Lin, Jia <lin.a.jia@intel.com>
>> Signed-off-by: Akashdeep Sharma <akashdeep.sharma@intel.com>
>> Reviewed-by: Jim Bride <jim.bride@linux.intel.com>
>> Reviewed-by: Jose Abreu <Jose.Abreu@synopsys.com>
>> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
>> Cc: Emil Velikov <emil.l.velikov@gmail.com>
>>
>> V2: Addressed review comments from Sean:
>> - Fix spellings/typo
>> - No need to handle aspect ratio none
>> - Add a break, for default case too
>> V3: Rebase
>> V4: Added r-b from Jose
>> ---
>>   drivers/gpu/drm/drm_modes.c | 31 +++++++++++++++++++++++++++++++
>>   1 file changed, 31 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
>> index 53f07ac..fde927a 100644
>> --- a/drivers/gpu/drm/drm_modes.c
>> +++ b/drivers/gpu/drm/drm_modes.c
>> @@ -997,6 +997,7 @@ bool drm_mode_equal_no_clocks_no_stereo(const struct drm_display_mode *mode1,
>>   	    mode1->vsync_end == mode2->vsync_end &&
>>   	    mode1->vtotal == mode2->vtotal &&
>>   	    mode1->vscan == mode2->vscan &&
>> +	    mode1->picture_aspect_ratio == mode2->picture_aspect_ratio &&
>>   	    (mode1->flags & ~DRM_MODE_FLAG_3D_MASK) ==
>>   	     (mode2->flags & ~DRM_MODE_FLAG_3D_MASK))
>>   		return true;
>> @@ -1499,6 +1500,21 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
>>   	out->vrefresh = in->vrefresh;
>>   	out->flags = in->flags;
>>   	out->type = in->type;
>> +	out->flags &= ~DRM_MODE_FLAG_PIC_AR_MASK;
>> +
>> +	switch (in->picture_aspect_ratio) {
>> +	case HDMI_PICTURE_ASPECT_4_3:
>> +		out->flags |= DRM_MODE_FLAG_PIC_AR_4_3;
>> +		break;
>> +	case HDMI_PICTURE_ASPECT_16_9:
>> +		out->flags |= DRM_MODE_FLAG_PIC_AR_16_9;
>> +		break;
>> +	case HDMI_PICTURE_ASPECT_RESERVED:
>> +	default:
>> +		out->flags |= DRM_MODE_FLAG_PIC_AR_NONE;
>> +		break;
>> +	}
>> +
>>   	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
>>   	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
>>   }
>> @@ -1544,6 +1560,21 @@ int drm_mode_convert_umode(struct drm_display_mode *out,
>>   	strncpy(out->name, in->name, DRM_DISPLAY_MODE_LEN);
>>   	out->name[DRM_DISPLAY_MODE_LEN-1] = 0;
>>   
>> +	/* Clearing picture aspect ratio bits from out flags */
>> +	out->flags &= ~DRM_MODE_FLAG_PIC_AR_MASK;
>> +
>> +	switch (in->flags & DRM_MODE_FLAG_PIC_AR_MASK) {
>> +	case DRM_MODE_FLAG_PIC_AR_4_3:
>> +		out->picture_aspect_ratio |= HDMI_PICTURE_ASPECT_4_3;
>> +		break;
>> +	case DRM_MODE_FLAG_PIC_AR_16_9:
>> +		out->picture_aspect_ratio |= HDMI_PICTURE_ASPECT_16_9;
>> +		break;
>> +	default:
>> +		out->picture_aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
>> +		break;
>> +	}
> Hmm. So now we have the mode aspect ratio infromation duplicated
> in two different places. Not sure that won't lead to some confusion.
In drm layer, this is the only place. Actually till now, DRM layer dint 
have the support for aspect ratio at all. This was causing
HDMI compliance tests like 7-27 fail, which expect a particular unique 
VIC in AVI infoframe on modeset.

I have given some details about this in cover-letter.
> Although we do want the user to be able to override via the property I
> suppose, so we'd have to change that (+ the inforframe code) to
> look at the mode flags instead if we would eliminate
> 'picture_aspect_ratio'.
I had a small discussion on this with Daniel, and we discussed that it 
doesnt make sense to override just the aspect ratio if the monitor 
doesn't even support that aspect ratio.
And currently the was how this property is implemented is, we just 
override the aspect ratio without any validity check.

Now as we have all the supported aspect ratio added properly in the mode 
info itself, we need not to have this property at all, So Daniel 
suggested me to remove that property too.
>
> And that brings me to the other point. At least i915 will simply
> override the mode's aspect ration with the property. So this looks like
> a big no-op for now on i915.
Yes, This is a bug in I915. When I published the first version of this 
series, I had one patch, which was overriding the value only when the 
property is set.
This should be the right case. And then Daniel suggested to remove the 
property all together (and it makes sense as we have proper aspect 
ratios in mode information
itself) So I kept that patch separate, to be merged separately.
>   It's looking like we might need a new
> propetty value to differentiate between "auto" and "none" for real.
Now we have the exact aspect ratio given by monitor EDID, so IMHO it 
would be better if we can just have real aspect.

Regards
Shashank
>> +
>>   	out->status = drm_mode_validate_basic(out);
>>   	if (out->status != MODE_OK)
>>   		goto out;
>> -- 
>> 1.9.1
>>
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