linux-kernel - Re: [PATCH v3 1/6] drm/msm/a6xx: Retrieve gmu core range by index

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Message-ID: <551b45ae-0980-4bd5-bb83-2fac6d7e2ce7@oss.qualcomm.com>
Date: Fri, 5 Dec 2025 13:03:11 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: rob.clark@....qualcomm.com
Cc: Akhil P Oommen <akhilpo@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Jessica Zhang <jesszhan0024@...il.com>,
        Dan Carpenter <dan.carpenter@...aro.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/6] drm/msm/a6xx: Retrieve gmu core range by index

On 12/4/25 3:34 PM, Rob Clark wrote:
> On Thu, Dec 4, 2025 at 5:30 AM Konrad Dybcio
> <konrad.dybcio@....qualcomm.com> wrote:
>>
>> On 12/4/25 2:10 PM, Akhil P Oommen wrote:
>>> On 11/22/2025 7:08 PM, Konrad Dybcio wrote:
>>>> On 11/21/25 10:52 PM, Akhil P Oommen wrote:
>>>>> Some GPUs like A612 doesn't use a named register range resource. This
>>>>> is because the reg-name property is discouraged when there is just a
>>>>> single resource.
>>>>>
>>>>> To address this, retrieve the 'gmu' register range by its index. It is
>>>>> always guaranteed to be at index 0.
>>>>>
>>>>> Signed-off-by: Akhil P Oommen <akhilpo@....qualcomm.com>
>>>>> ---
>>>>>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 14 ++++++--------
>>>>>  1 file changed, 6 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>>> index 5903cd891b49..9662201cd2e9 100644
>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>>> @@ -2029,21 +2029,19 @@ static int cxpd_notifier_cb(struct notifier_block *nb,
>>>>>     return 0;
>>>>>  }
>>>>>
>>>>> -static void __iomem *a6xx_gmu_get_mmio(struct platform_device *pdev,
>>>>> -           const char *name, resource_size_t *start)
>>>>> +static void __iomem *a6xx_gmu_get_mmio(struct platform_device *pdev, resource_size_t *start)
>>>>
>>>> Can we drop this and just use devm_platform_get_and_ioremap_resource()?
>>>
>>> This API seems to lock the io region and fails with -EBUSY if the region
>>> is already in use. I am worried it may regress other chipsets. So, I
>>> dropped this idea at the last moment.
>>
>> Is there any specific platform where this would be an issue?
> 
> IIRC we've had this problem before and ended up reverting a similar
> change, due to gpucc and gpu overlap

Argh, sm8350.dtsi for example seems to be affected..

Hopefully one day we can fix that..

Konrad