linux-kernel - Re: [PATCH v2 08/34] drm/msm: Remove vram carveout support

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Message-Id: <D98YGSPT9OB6.26E97T9QSD4NW@fairphone.com>
Date: Thu, 17 Apr 2025 15:41:29 +0200
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Dmitry Baryshkov" <dmitry.baryshkov@....qualcomm.com>, "Rob Clark"
 <robdclark@...il.com>
Cc: <dri-devel@...ts.freedesktop.org>, <freedreno@...ts.freedesktop.org>,
 <linux-arm-msm@...r.kernel.org>, "Rob Clark" <robdclark@...omium.org>,
 "Sean Paul" <sean@...rly.run>, "Konrad Dybcio" <konradybcio@...nel.org>,
 "Abhinav Kumar" <quic_abhinavk@...cinc.com>, "Dmitry Baryshkov"
 <lumag@...nel.org>, "Marijn Suijten" <marijn.suijten@...ainline.org>,
 "David Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>,
 "open list" <linux-kernel@...r.kernel.org>, <luca@...aweiss.eu>
Subject: Re: [PATCH v2 08/34] drm/msm: Remove vram carveout support

On Thu Apr 17, 2025 at 1:20 AM CEST, Dmitry Baryshkov wrote:
> On Wed, Mar 19, 2025 at 07:52:20AM -0700, Rob Clark wrote:
>> From: Rob Clark <robdclark@...omium.org>
>> 
>> It is standing in the way of drm_gpuvm / VM_BIND support.  Not to
>> mention frequently broken and rarely tested.  And I think only needed
>> for a 10yr old not quite upstream SoC (msm8974).
>
> Well... MSM8974 is quite upstream, but anyway, let's drop it. Maybe
> somebody will write an IOMMU driver.

msm8226 is also using this!

Sad to see this happening, but I get the reasoning. Unfortunately nobody
who really knows GPU and IOMMU bits has looked at this in recent years,
for msm8974 we (mostly Matti Lehtimäki and me) have a semi-working
branch but hitting random issues with it.

Would've been nice if somebody made functional IOMMU support back in
like 2015-2016 when more people looked at this platform.

Regards
Luca

>
>> 
>> Maybe we can add support back in later, but I'm doubtful.
>> 
>> Signed-off-by: Rob Clark <robdclark@...omium.org>
>> ---
>>  drivers/gpu/drm/msm/adreno/a2xx_gpu.c      |   6 +-
>>  drivers/gpu/drm/msm/adreno/a3xx_gpu.c      |  13 +-
>>  drivers/gpu/drm/msm/adreno/a4xx_gpu.c      |  13 +-
>>  drivers/gpu/drm/msm/adreno/adreno_device.c |   4 -
>>  drivers/gpu/drm/msm/adreno/adreno_gpu.h    |   1 -
>>  drivers/gpu/drm/msm/msm_drv.c              | 117 +-----------------
>>  drivers/gpu/drm/msm/msm_drv.h              |  11 --
>>  drivers/gpu/drm/msm/msm_gem.c              | 131 ++-------------------
>>  drivers/gpu/drm/msm/msm_gem.h              |   5 -
>>  drivers/gpu/drm/msm/msm_gem_submit.c       |   5 -
>>  10 files changed, 19 insertions(+), 287 deletions(-)