[PATCH] drm/amd/display: Enable ogam_ram for dcn32+dcn35+dcn351

Fri Apr 12 20:22:02 UTC 2024

On 2024-04-12 12:26, Melissa Wen wrote:
> On 04/12, Joshua Ashton wrote:
>>
>>
>> On 4/11/24 3:26 PM, Melissa Wen wrote:
>>> On 04/10, Joshua Ashton wrote:
>>>> The comment here states "no OGAM in DPP since DCN1", yet that is not
>>>> true.
>>>>
>>>> Testing on an RX 7900XTX (dcn32), it actually does exist in hardware and
>>>> works fine.
>>>> My best guess is the comment is confused with OGAM ROM for DPP, rather
>>>> than OGAM RAM.
>>>>
>>>> I did not test dcn35/351 as I do not have that hardware, but I assume
>>>> the same follows there given the seemingly erroneous comment.
>>>> Someone at AMD should check that before merging this commit.
>>>
>>> hmm... I don't have any of these hw versions, but AFAIU if there is
>>> ogam/blend lut block in dcn32, the helper implementation for programming
>>> it properly (i.e. dpp_program_blnd_lut) is also missing here:
>>> - https://gitlab.freedesktop.org/agd5f/linux/-/blob/amd-staging-drm-next/drivers/gpu/drm/amd/display/dc/dpp/dcn32/dcn32_dpp.c#L125
>>> right? So, it's good if AMD people can check it too.
>>>
>>> Melissa
>>
>> Hmm, yes. But, see dcn32_set_mcm_luts, that seems to handle per-plane blend
>> + shaper + 3D LUT state which is equivalent to what existed before?
> 
> oh, cool! nice finding. blnd_lut is set on plane state, but programmed
> on MPC now.
> 
> But I see the color pipeline changed in many stages from this version:
> - shaper + 3dlut before **or** after blending, but not before **and** after?
> - where post-blending gamut_remap_matrix is located now in this
>   pipeline with mpcc postblend_1dlut and shaper+3dlut with mutable
>   position?
>   I guess something like:
>   - [shaper -> 3dlut -> blnd_lut] -> ctm -> regamma ??

[1dlut -> 3dlut -> 1dlut] is now a movable block, called Movable CM
(color management), or MCM for short. It can occur before blending or
after. Because of that it moved to MPC (multi-plane combiner).

If it's positioned for pre-blending it looks like this:

DPP -> MCM -> BLND -> Blending -> Gamut Remap -> Out Gam -> OPP -> ...

If it's positioned for post-blending it looks like this:

DPP -> BLND -> Blending -> MCM -> Gamut Remap -> Out Gam -> OPP

This is the case since DCN 3.2.

Because of that you don't have an ogam_ram in dpp anymore for DCN 3.2
and newer.

>>
>> Therefore, I think I am actually wrong with enabling the ogam_ram in DPP cap
>> here, and the right solution is to change the check for exposing the
>> property to account for these LUTs being available per-plane with mcm.
>>
>> (what is mcm btw...? lots of acronyms and stuff moving around in hw hehe)
> 
> yes, shaper, 3dlut, blend_lut don't seem DPP caps anymore. MCM looks
> like a component of MPC, so I think we need new mpc.color caps to
> describe them properly (?)
> 
> I also didn't find in the Linux/AMD glossary or code comment that
> describe what MCM is...
> 
>>
>> What's a good way for us to check for that? Seems like the caps don't help
>> much there. We could check for the literal function ptr I guess...?
>>
>> What are your thoughts, Harry and Melissa?
> 

I wonder if it makes sense to add an mcm cap to mpc_color_caps. Will need to
chat with some people about that.

Harry

> yeah, AFAIK color caps values are manually set and may contain
> misleading information. I'm unsure that using function ptr would solve
> the issue of having undocumented caps introduced to the color pipeline,
> such as MCM, but your suggestion seems more reliable.
> 
> Anyway, the timing where the color pipeline was merged didn't help, but
> if new caps and functions are not documented and the DM handles are not
> updated accordingly, we will have the same issue in the future. 
> For example, I see two new ptrs were introduced and implemented here:
> - https://gitlab.freedesktop.org/agd5f/linux/-/commit/a820190204aef
> - https://gitlab.freedesktop.org/agd5f/linux/-/commit/90f33674a0756
> and we would need to update the DM color mgmt anyway to check these
> new/unknown functions.
> 
> Seems okay if we check program_1dlut instead of ogam_ram caps, but what
> should we do for dpp/mpc shaper+3d lut in set_mcm_luts? I mean, should
> we enable plane or CRTC shaper+3dlut on DM? x_X
> 
> Anyway, thanks for all these findings!
> 
> I would like to hear more from AMD too.
> 
> Melissa
> 
>>
>> - Joshie 🐸✨
>>
>>>
>>>>
>>>> Signed-off-by: Joshua Ashton <joshua at froggi.es>
>>>>
>>>> Cc: Harry Wentland <harry.wentland at amd.com>
>>>> Cc: Xaver Hugl <xaver.hugl at gmail.com>
>>>> Cc: Melissa Wen <mwen at igalia.com>
>>>> Cc: Ethan Lee <flibitijibibo at gmail.com>
>>>> ---
>>>>   drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c  | 2 +-
>>>>   drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c  | 2 +-
>>>>   .../gpu/drm/amd/display/dc/resource/dcn351/dcn351_resource.c    | 2 +-
>>>>   3 files changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
>>>> index 9aa39bd25be9..94f5d2b5aadf 100644
>>>> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
>>>> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn32/dcn32_resource.c
>>>> @@ -2182,7 +2182,7 @@ static bool dcn32_resource_construct(
>>>>   	dc->caps.color.dpp.dgam_rom_for_yuv = 0;
>>>>   	dc->caps.color.dpp.hw_3d_lut = 1;
>>>> -	dc->caps.color.dpp.ogam_ram = 0;  // no OGAM in DPP since DCN1
>>>> +	dc->caps.color.dpp.ogam_ram = 1;
>>>>   	// no OGAM ROM on DCN2 and later ASICs
>>>>   	dc->caps.color.dpp.ogam_rom_caps.srgb = 0;
>>>>   	dc->caps.color.dpp.ogam_rom_caps.bt2020 = 0;
>>>> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
>>>> index 25ac450944e7..708d63cc3f7f 100644
>>>> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
>>>> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn35/dcn35_resource.c
>>>> @@ -1861,7 +1861,7 @@ static bool dcn35_resource_construct(
>>>>   	dc->caps.color.dpp.dgam_rom_for_yuv = 0;
>>>>   	dc->caps.color.dpp.hw_3d_lut = 1;
>>>> -	dc->caps.color.dpp.ogam_ram = 0;  // no OGAM in DPP since DCN1
>>>> +	dc->caps.color.dpp.ogam_ram = 1;
>>>>   	// no OGAM ROM on DCN301
>>>>   	dc->caps.color.dpp.ogam_rom_caps.srgb = 0;
>>>>   	dc->caps.color.dpp.ogam_rom_caps.bt2020 = 0;
>>>> diff --git a/drivers/gpu/drm/amd/display/dc/resource/dcn351/dcn351_resource.c b/drivers/gpu/drm/amd/display/dc/resource/dcn351/dcn351_resource.c
>>>> index 8a57adb27264..053e8ec6d1ef 100644
>>>> --- a/drivers/gpu/drm/amd/display/dc/resource/dcn351/dcn351_resource.c
>>>> +++ b/drivers/gpu/drm/amd/display/dc/resource/dcn351/dcn351_resource.c
>>>> @@ -1841,7 +1841,7 @@ static bool dcn351_resource_construct(
>>>>   	dc->caps.color.dpp.dgam_rom_for_yuv = 0;
>>>>   	dc->caps.color.dpp.hw_3d_lut = 1;
>>>> -	dc->caps.color.dpp.ogam_ram = 0;  // no OGAM in DPP since DCN1
>>>> +	dc->caps.color.dpp.ogam_ram = 1;
>>>>   	// no OGAM ROM on DCN301
>>>>   	dc->caps.color.dpp.ogam_rom_caps.srgb = 0;
>>>>   	dc->caps.color.dpp.ogam_rom_caps.bt2020 = 0;
>>>> -- 
>>>> 2.44.0
>>>>