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

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Message-ID: <7b4bcb6e-fbb1-45f6-921e-dd1340a8cece@oss.qualcomm.com>
Date: Thu, 4 Dec 2025 14:30:38 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>
Cc: Rob Clark <robin.clark@....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 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?

Konrad