linux-kernel - Re: [git pull] drm for 6.17-rc1

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Message-ID: <11a42824-b240-43f0-980a-8222be872483@kernel.org>
Date: Thu, 31 Jul 2025 18:11:41 +0530
From: Mario Limonciello <superm1@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
 Dave Airlie <airlied@...il.com>, Dillon Varone <dillon.varone@....com>,
 Ivan Lipski <ivan.lipski@....com>, Daniel Wheeler <daniel.wheeler@....com>,
 Alex Deucher <alexander.deucher@....com>, Wenjing Liu <wenjing.liu@....com>
Cc: Simona Vetter <simona@...ll.ch>,
 dri-devel <dri-devel@...ts.freedesktop.org>,
 LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] drm for 6.17-rc1



On 7/31/25 10:37 AM, Linus Torvalds wrote:
> On Wed, 30 Jul 2025 at 21:58, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> d7b618bc41ee3d44c070212dff93949702ede997 is the first bad commit
>>      drm/amd/display: Refactor DSC cap calculations
>>
>> Let me go see how painful it is to just revert it from top-of-tree.
> 
> So with that reverted (didn't require a lot of fixing, only minor
> unrelated context added nearby later), current top-of-tree works for
> me again.
> 
> The revert I used for testing attached just so people can see exactly
> what I did.
> 
> It's late here, I wasn't getting any more work done today anyway, so
> I'll leave it like this for now.
> 
> I can continue to do the merge window with this revert purely local
> for a while, so if somebody comes up with a proper fix, I can test
> that out.
> 
>              Linus

Pure guess from looking at the diff from 
d7b618bc41ee3d44c070212dff93949702ede997, maybe the NULL ptr is a deref 
on a pointer that doesn't have funcs declared being an older GPU.  So 
maybe check for funcs?

diff --git a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c 
b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
index a454d16e6586..95d51de26c0b 100644
--- a/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
+++ b/drivers/gpu/drm/amd/display/dc/dsc/dc_dsc.c
@@ -673,7 +673,7 @@ static void get_dsc_enc_caps(
                 return;

         /* check if reported cap global or only for a single DCN DSC enc */
-       if (dsc->funcs->dsc_get_enc_caps) {
+       if (dsc->funcs && dsc->funcs->dsc_get_enc_caps) {
                 if (!dsc->ctx->dc->debug.disable_dsc)
                         dsc->funcs->dsc_get_enc_caps(dsc_enc_caps, 
pixel_clock_100Hz);
         } else {