linux-kernel - Re: [PATCH v2 1/3] drm/panfrost: Ignore core_mask for poweroff and disable PWRTRANS irq

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Message-ID: <20231128142753.5cd0c2fd@collabora.com>
Date:   Tue, 28 Nov 2023 14:27:53 +0100
From:   Boris Brezillon <boris.brezillon@...labora.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
Cc:     robh@...nel.org, steven.price@....com,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, m.szyprowski@...sung.com,
        krzysztof.kozlowski@...aro.org
Subject: Re: [PATCH v2 1/3] drm/panfrost: Ignore core_mask for poweroff and
 disable PWRTRANS irq

On Tue, 28 Nov 2023 13:45:08 +0100
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
wrote:

> Some SoCs may be equipped with a GPU containing two core groups
> and this is exactly the case of Samsung's Exynos 5422 featuring
> an ARM Mali-T628 MP6 GPU: the support for this GPU in Panfrost
> is partial, as this driver currently supports using only one
> core group and that's reflected on all parts of it, including
> the power on (and power off, previously to this patch) function.
> 
> The issue with this is that even though executing the soft reset
> operation should power off all cores unconditionally, on at least
> one platform we're seeing a crash that seems to be happening due
> to an interrupt firing which may be because we are calling power
> transition only on the first core group, leaving the second one
> unchanged, or because ISR execution was pending before entering
> the panfrost_gpu_power_off() function and executed after powering
> off the GPU cores, or all of the above.
> 
> Finally, solve this by:
>  - Avoid to enable the power transition interrupt on reset; and
>  - Ignoring the core_mask and ask the GPU to poweroff both core groups
> 
> Fixes: 22aa1a209018 ("drm/panfrost: Really power off GPU cores in panfrost_gpu_power_off()")
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>

Reviewed-by: Boris Brezillon <boris.brezillon@...labora.com>

> ---
>  drivers/gpu/drm/panfrost/panfrost_gpu.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panfrost/panfrost_gpu.c b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> index 09f5e1563ebd..bd41617c5e4b 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_gpu.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_gpu.c
> @@ -78,7 +78,12 @@ int panfrost_gpu_soft_reset(struct panfrost_device *pfdev)
>  	}
>  
>  	gpu_write(pfdev, GPU_INT_CLEAR, GPU_IRQ_MASK_ALL);
> -	gpu_write(pfdev, GPU_INT_MASK, GPU_IRQ_MASK_ALL);
> +
> +	/* Only enable the interrupts we care about */
> +	gpu_write(pfdev, GPU_INT_MASK,
> +		  GPU_IRQ_MASK_ERROR |
> +		  GPU_IRQ_PERFCNT_SAMPLE_COMPLETED |
> +		  GPU_IRQ_CLEAN_CACHES_COMPLETED);
>  
>  	/*
>  	 * All in-flight jobs should have released their cycle
> @@ -425,11 +430,10 @@ void panfrost_gpu_power_on(struct panfrost_device *pfdev)
>  
>  void panfrost_gpu_power_off(struct panfrost_device *pfdev)
>  {
> -	u64 core_mask = panfrost_get_core_mask(pfdev);
>  	int ret;
>  	u32 val;
>  
> -	gpu_write(pfdev, SHADER_PWROFF_LO, pfdev->features.shader_present & core_mask);
> +	gpu_write(pfdev, SHADER_PWROFF_LO, pfdev->features.shader_present);
>  	ret = readl_relaxed_poll_timeout(pfdev->iomem + SHADER_PWRTRANS_LO,
>  					 val, !val, 1, 1000);
>  	if (ret)
> @@ -441,7 +445,7 @@ void panfrost_gpu_power_off(struct panfrost_device *pfdev)
>  	if (ret)
>  		dev_err(pfdev->dev, "tiler power transition timeout");
>  
> -	gpu_write(pfdev, L2_PWROFF_LO, pfdev->features.l2_present & core_mask);
> +	gpu_write(pfdev, L2_PWROFF_LO, pfdev->features.l2_present);
>  	ret = readl_poll_timeout(pfdev->iomem + L2_PWRTRANS_LO,
>  				 val, !val, 0, 1000);
>  	if (ret)