linux-kernel - Re: [PATCH 10/17] drm/msm/a6xx: Rebase GMU register offsets

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Message-ID: <5a027440-8720-4df9-a793-5ac3a624ef60@oss.qualcomm.com>
Date: Wed, 8 Oct 2025 13:51:16 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Sean Paul <sean@...rly.run>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar
 <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse
 <jordan@...micpenguin.net>,
        Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>
Cc: linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 10/17] drm/msm/a6xx: Rebase GMU register offsets

On 9/30/25 7:48 AM, Akhil P Oommen wrote:
> GMU registers are always at a fixed offset from the GPU base address,
> a consistency maintained at least within a given architecture generation.
> In A8x family, the base address of the GMU has changed, but the offsets
> of the gmu registers remain largely the same. To enable reuse of the gmu
> code for A8x chipsets, update the gmu register offsets to be relative
> to the GPU's base address instead of GMU's.
> 
> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c             |  44 +++-
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.h             |  20 +-
>  drivers/gpu/drm/msm/registers/adreno/a6xx_gmu.xml | 248 +++++++++++-----------
>  3 files changed, 172 insertions(+), 140 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index fc717c9474ca5bdd386a8e4e19f43abce10ce591..72d64eb10ca931ee90c91f7e004771cf6d7997a4 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -585,14 +585,14 @@ static inline void pdc_write(void __iomem *ptr, u32 offset, u32 value)
>  }
>  
>  static void __iomem *a6xx_gmu_get_mmio(struct platform_device *pdev,
> -		const char *name);
> +		const char *name, resource_size_t *start);

Maybe you can keep this offset variant and switch to a simple

devm_platform_get_and_ioremap_resource()

for others (also letting us get rid of a number of iounmap() calls)

[...]

> +	/* The 'offset' is based on GPU's start address. Adjust it */

That's what an offset is, no? ;)

I think we can drop this comment or move it above the #define

Konrad