Re: [PATCH 03/16] drm/i915/skl+: add NV12 in skl_format_to_fourcc

Sharma, Shashank
2018-02-08T04:32:45Z

On 2/8/2018 8:50 AM, Srinivas, Vidya wrote:
>
>> -----Original Message-----
>> From: Sharma, Shashank
>> Sent: Wednesday, February 7, 2018 9:22 PM
>> To: Srinivas, Vidya <vidya.srinivas@intel.com>; intel-
>> gfx@lists.freedesktop.org
>> Cc: maarten.lankhorst@linux.intel.com; Kamath, Sunil
>> <sunil.kamath@intel.com>; Shankar, Uma <uma.shankar@intel.com>;
>> Kumar, Mahesh1 <mahesh1.kumar@intel.com>
>> Subject: Re: [PATCH 03/16] drm/i915/skl+: add NV12 in
>> skl_format_to_fourcc
>>
>> Regards
>>
>> Shashank
>>
>>
>> On 2/6/2018 6:28 PM, Vidya Srinivas wrote:
>>> From: Mahesh Kumar <mahesh1.kumar@intel.com>
>>>
>>> Add support of recognizing DRM_FORMAT_NV12 from plane_format
>> register
>>> value.
>>>
>>> Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
>>> ---
>>> drivers/gpu/drm/i915/intel_display.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_display.c
>>> b/drivers/gpu/drm/i915/intel_display.c
>>> index 60ba5bb..e3a6a7f 100644
>>> --- a/drivers/gpu/drm/i915/intel_display.c
>>> +++ b/drivers/gpu/drm/i915/intel_display.c
>>> @@ -2626,6 +2626,8 @@ static int skl_format_to_fourcc(int format, bool
>> rgb_order, bool alpha)
>>> switch (format) {
>>> case PLANE_CTL_FORMAT_RGB_565:
>>> return DRM_FORMAT_RGB565;
>>> + case PLANE_CTL_FORMAT_NV12:
>>> + return DRM_FORMAT_NV12;
>> I dont think this is correct, the case PLANE_CTL_FORMAT_NV12 is defined as
>> (1 << 24) but when I check bspec definition, 24th bit is set for
>> P010/12/16 formats. AFAIK NV12 is 8 bit format whereas P0xx formats are
>> 10/12/16 bit formats (they both are YCBCR 4:2:0 of course). This means we
>> have mixed NV12 format with P0xx formats. When I checked the definition
>> of DRM_FORMAT_NV12, I am not sure if that's intended for this. Ville, I saw
>> that the DRM_FORMAT_NV12 definition was added by you, can you please
>> comment if this is the right usage ?
>>
> Upto Gen10 24-27 bits of PLANE_CTL will be used for format. ICL onwards 23rd bit
> is also used. PLANE_CTL_FORMAT_MASK has been defined in i915_reg.h
> and mapping will be same if 23rd bit is 0. For NV12, 1<< 24 thus holds good
> for all Gen.
That's not my point. What I want to say is, as per bspec (1 << 24) is
for P010/P012/P016 formats, not NV12. NV12 is 8 bit YCBCR 4:2:0 format
whereas P010/012/016 are 10,12 and 16 bit YCBCR 4:2:0 formats. So I was
not sure if that should be called NV12 and hence I was not sure if we
should return DRM_FORMAT_NV12 for the same.
- Shashank
>>> default:
>>> case PLANE_CTL_FORMAT_XRGB_8888:
>>> if (rgb_order) {