linux-kernel - Re: [PATCH v2] drm/panthor: attach the driver's multiple power domains

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Message-ID: <77faf362-05bc-45b8-bddd-eed66ae70a63@arm.com>
Date: Mon, 20 Oct 2025 08:59:41 +0100
From: Steven Price <steven.price@....com>
To: Rain Yang <jiyu.yang@....nxp.com>, imx@...ts.linux.dev,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Cc: boris.brezillon@...labora.com, liviu.dudau@....com,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de,
 airlied@...il.com, simona@...ll.ch, xianzhong.li@....com,
 Rain Yang <jiyu.yang@....com>, Prabhu Sundararaj <prabhu.sundararaj@....com>
Subject: Re: [PATCH v2] drm/panthor: attach the driver's multiple power
 domains

On 13/10/2025 10:34, Rain Yang wrote:
> From: Rain Yang <jiyu.yang@....com>
> 
> Some platforms, such as i.MX95, utilize multiple power domains that need
> to be attached explicitly. This patch ensures that the driver properly
> attaches all available power domains using devm_pm_domain_attach_list().
> 
> Suggested-by: Boris Brezillon <boris.brezillon@...labora.com>
> Signed-off-by: Prabhu Sundararaj <prabhu.sundararaj@....com>
> Signed-off-by: Rain Yang <jiyu.yang@....com>
> ---
>  drivers/gpu/drm/panthor/panthor_device.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
> index f0b2da5b2b96..fbbc84e9efbe 100644
> --- a/drivers/gpu/drm/panthor/panthor_device.c
> +++ b/drivers/gpu/drm/panthor/panthor_device.c
> @@ -167,6 +167,7 @@ static void panthor_device_free_page(struct drm_device *ddev, void *data)
>  int panthor_device_init(struct panthor_device *ptdev)
>  {
>  	u32 *dummy_page_virt;
> +	struct dev_pm_domain_list  *pd_list = NULL;
>  	struct resource *res;
>  	struct page *p;
>  	int ret;
> @@ -218,6 +219,12 @@ int panthor_device_init(struct panthor_device *ptdev)
>  	if (ret)
>  		return ret;
>  
> +	ret = devm_pm_domain_attach_list(ptdev->base.dev, NULL, &pd_list);
> +	if (ret < 0) {
> +		drm_err(&ptdev->base, "attach power domains failed, ret=%d", ret);
> +		return ret;

This fails on the rock-5b. I believe because the PM code automatically 
attaches a single power domain (as on the rock-5b) so this then returns 
-EEXIST:

[   11.433501] panthor fb000000.gpu: [drm] *ERROR* attach power domains failed, ret=-17

I notice that the tegra driver checks dev->pm_domain and only calls 
devm_pm_domain_attach_list if that is NULL.

Thanks,
Steve

> +	}
> +
>  	ret = panthor_devfreq_init(ptdev);
>  	if (ret)
>  		return ret;