linux-kernel - Re: [PATCH v2 2/2] drm/msm/mdp4: Support NV12MT format in mdp4

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Message-id: <55121CDA.4020703@samsung.com>
Date:	Wed, 25 Mar 2015 11:26:34 +0900
From:	Seung-Woo Kim <sw0312.kim@...sung.com>
To:	Rob Clark <robdclark@...il.com>
Cc:	Stephane Viau <sviau@...eaurora.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Beeresh Gopal <gbeeresh@...eaurora.org>,
	Inki Dae <inki.dae@...sung.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Seung-Woo Kim <sw0312.kim@...sung.com>,
	m.szyprowski@...sung.com, s.nawrocki@...sung.com,
	k.debski@...sung.com
Subject: Re: [PATCH v2 2/2] drm/msm/mdp4: Support NV12MT format in mdp4

Hello,

On 2015년 03월 25일 03:32, Rob Clark wrote:
> On Mon, Mar 16, 2015 at 4:05 AM, Daniel Vetter <daniel@...ll.ch> wrote:
>> On Fri, Mar 13, 2015 at 03:12:10PM -0400, Stephane Viau wrote:
>>> From: Beeresh Gopal <gbeeresh@...eaurora.org>
>>>
>>> Using fb modifier flag, support NV12MT format in MDP4.
>>>
>>> v2:
>>> - rework the modifier's description [Daniel Vetter's comment]
>>> - drop .set_mode_config() callback [Rob Clark's comment]
>>>
>>> Signed-off-by: Beeresh Gopal <gbeeresh@...eaurora.org>
>>> Signed-off-by: Stephane Viau <sviau@...eaurora.org>
>>> ---
>>>  drivers/gpu/drm/msm/mdp/mdp4/mdp4_kms.c   |  2 ++
>>>  drivers/gpu/drm/msm/mdp/mdp4/mdp4_plane.c | 22 ++++++++++++++++++++++
>>>  include/uapi/drm/drm_fourcc.h             |  5 +++++
>>>  3 files changed, 29 insertions(+)
>>>

<snip.>

>>> diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
>>> index 188e61f..2ff79cb 100644
>>> --- a/include/uapi/drm/drm_fourcc.h
>>> +++ b/include/uapi/drm/drm_fourcc.h
>>> @@ -161,4 +161,9 @@
>>>   * authoritative source for all of these.
>>>   */
>>>
>>> +/* Samsung framebuffer modifiers */
>>> +
>>> +/* Tiled: 64x32 pixel macroblocks */
>>
>> Since this seems shared by a lot of vendors (I still don't believe Samsung
>> invented this really ...) can you please describe this thing a bit in more
>> detail? Somewhat important how macroblocks are laid out and pixels within.
>> Also with a planar format like NV12 "pixel" is a bit unclear, e.g. what
>> happens if you throw 10bit plane formats at this? So maybe also add a note
>> that for now this is only used together with NV12T.
> 
> + a couple folks from Samsung, since I expect they want this for
> exynos as well (and might be able to help with the description)

Yes, I have a plan to apply fb_modifier for exynos with kms interface of
hdmi.

> 
> vl4 also has this format, but last I looked was rather light on the details.

I am not sure msm mdp uses exactly same format with exynos, but anyway
v4l2 NV12MT format was introduced for exynos hw video codec.

macro blocks for the format is laid z-order and each pixel data in each
macro block is just normal NV12 style.

I think Marek and Sylwester can help understanding the format.

> 
> http://linuxtv.org/downloads/v4l-dvb-apis/re31.html
> 
> I know up in userspace, GStreamer seems to have some support for this format:
> 
> http://cgit.freedesktop.org/gstreamer/gst-plugins-base/commit/?id=f8d3b9b4fcc5e08b771314fa95e9ed8f750b54e6
> 
>> Then there's the question of validating the input - stride should probably
>> be a full multiple of the macroblock size. Since this is a shared format
>> imo this kind of checking should be done in drm core.
> 
> afaiu, stride (and maybe even width?) should be a multiple of the
> block size (but height does not)
> 
> BR,
> -R
> 
> 
>> -Daniel
>>
>>
>>> +#define DRM_FORMAT_MOD_SAMSUNG_64_32_TILE fourcc_mod_code(SAMSUNG, 1)
>>> +
>>>  #endif /* DRM_FOURCC_H */
>>> --
>>> Qualcomm Innovation Center, Inc.
>>>
>>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
>>>
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> 

-- 
Seung-Woo Kim
Samsung Software R&D Center
--

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