linux-kernel - Re: [PATCH RFT 04/14] drm/msm/a6xx: Get a handle to the common UBWC config

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Message-ID: <CAF6AEGvmEP4oGytfsCHYDCtOUDYq68y=vS7fu0jzP+=oajeq9g@mail.gmail.com>
Date: Fri, 9 May 2025 06:52:23 -0700
From: Rob Clark <robdclark@...il.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Konrad Dybcio <konradybcio@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Dmitry Baryshkov <lumag@...nel.org>, 
	Akhil P Oommen <quic_akhilpo@...cinc.com>, Sean Paul <sean@...rly.run>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org
Subject: Re: [PATCH RFT 04/14] drm/msm/a6xx: Get a handle to the common UBWC config

On Fri, May 9, 2025 at 5:31 AM Konrad Dybcio
<konrad.dybcio@....qualcomm.com> wrote:
>
> On 5/8/25 8:41 PM, Rob Clark wrote:
> > On Thu, May 8, 2025 at 11:13 AM Konrad Dybcio <konradybcio@...nel.org> wrote:
> >>
> >> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> >>
> >> Start the great despaghettification by getting a pointer to the common
> >> UBWC configuration, which houses e.g. UBWC versions that we need to
> >> make decisions.
> >>
> >> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> >> ---
> >>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c   | 16 ++++++++++++++--
> >>  drivers/gpu/drm/msm/adreno/adreno_gpu.c |  6 ++++++
> >>  drivers/gpu/drm/msm/adreno/adreno_gpu.h |  3 +++
> >>  3 files changed, 23 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> index b161b5cd991fc645dfcd69754b82be9691775ffe..89eb725f0950f3679d6214366cfbd22d5bcf4bc7 100644
> >> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> @@ -585,8 +585,13 @@ static void a6xx_set_cp_protect(struct msm_gpu *gpu)
> >>         gpu_write(gpu, REG_A6XX_CP_PROTECT(protect->count_max - 1), protect->regs[i]);
> >>  }
> >>
> >> -static void a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
> >> +static int a6xx_calc_ubwc_config(struct adreno_gpu *gpu)
> >>  {
> >> +       /* Inherit the common config and make some necessary fixups */
> >> +       gpu->common_ubwc_cfg = qcom_ubwc_config_get_data();
> >
> > This does look a bit funny given the devm_kzalloc() below.. I guess
> > just so that the ptr is never NULL?
>
> Yeah, would you prefer this is changed?

I think having an all zeros ubwc cfg isn't really going to work
anyways, so probably drop the kzalloc().  Or if there is a case that
I'm not thinking of offhand where it makes sense to have an all 0's
cfg, then add a comment to avoid future head scratching, since
otherwise it looks like a bug to be fixed.

BR,
-R