linux-kernel - Re: [PATCH] drm/mediatek: make imported PRIME buffers contiguous

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Message-ID: <1563947367.1070.7.camel@mtksdaap41>
Date:   Wed, 24 Jul 2019 13:49:27 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Alexandre Courbot <acourbot@...omium.org>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Tomasz Figa <tfiga@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/mediatek: make imported PRIME buffers contiguous

Hi, Alexandre:

On Tue, 2019-07-23 at 14:34 +0900, Alexandre Courbot wrote:
> This driver requires imported PRIME buffers to appear contiguously in
> its IO address space. Make sure this is the case by setting the maximum
> DMA segment size to a better value than the default 64K on the DMA
> device, and use said DMA device when importing PRIME buffers.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 47 ++++++++++++++++++++++++--
>  drivers/gpu/drm/mediatek/mtk_drm_drv.h |  2 ++
>  2 files changed, 46 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index 95fdbd0fbcac..4ad4770fab13 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -213,6 +213,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>  	struct mtk_drm_private *private = drm->dev_private;
>  	struct platform_device *pdev;
>  	struct device_node *np;
> +	struct device *dma_dev;
>  	int ret;
>  
>  	if (!iommu_present(&platform_bus_type))
> @@ -275,7 +276,27 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>  		goto err_component_unbind;
>  	}
>  
> -	private->dma_dev = &pdev->dev;
> +	dma_dev = &pdev->dev;
> +	private->dma_dev = dma_dev;
> +
> +	/*
> +	 * Configure the DMA segment size to make sure we get contiguous IOVA
> +	 * when importing PRIME buffers.
> +	 */
> +	if (!dma_dev->dma_parms) {
> +		private->dma_parms_allocated = true;
> +		dma_dev->dma_parms =
> +			devm_kzalloc(drm->dev, sizeof(*dma_dev->dma_parms),
> +				     GFP_KERNEL);
> +	}
> +	if (!dma_dev->dma_parms)
> +		goto err_component_unbind;

return with ret = 0?

> +
> +	ret = dma_set_max_seg_size(dma_dev, (unsigned int)DMA_BIT_MASK(32));
> +	if (ret) {
> +		dev_err(dma_dev, "Failed to set DMA segment size\n");
> +		goto err_unset_dma_parms;
> +	}
>  
>  	/*
>  	 * We don't use the drm_irq_install() helpers provided by the DRM
> @@ -285,13 +306,16 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>  	drm->irq_enabled = true;
>  	ret = drm_vblank_init(drm, MAX_CRTC);
>  	if (ret < 0)
> -		goto err_component_unbind;
> +		goto err_unset_dma_parms;
>  
>  	drm_kms_helper_poll_init(drm);
>  	drm_mode_config_reset(drm);
>  
>  	return 0;
>  
> +err_unset_dma_parms:
> +	if (private->dma_parms_allocated)
> +		dma_dev->dma_parms = NULL;
>  err_component_unbind:
>  	component_unbind_all(drm->dev, drm);
>  err_config_cleanup:
> @@ -302,9 +326,14 @@ static int mtk_drm_kms_init(struct drm_device *drm)
>  
>  static void mtk_drm_kms_deinit(struct drm_device *drm)
>  {
> +	struct mtk_drm_private *private = drm->dev_private;
> +
>  	drm_kms_helper_poll_fini(drm);
>  	drm_atomic_helper_shutdown(drm);
>  
> +	if (private->dma_parms_allocated)
> +		private->dma_dev->dma_parms = NULL;
> +
>  	component_unbind_all(drm->dev, drm);
>  	drm_mode_config_cleanup(drm);
>  }
> @@ -320,6 +349,18 @@ static const struct file_operations mtk_drm_fops = {
>  	.compat_ioctl = drm_compat_ioctl,
>  };
>  
> +/*
> + * We need to override this because the device used to import the memory is
> + * not dev->dev, as drm_gem_prime_import() expects.
> + */
> +struct drm_gem_object *mtk_drm_gem_prime_import(struct drm_device *dev,
> +						struct dma_buf *dma_buf)
> +{
> +	struct mtk_drm_private *private = dev->dev_private;
> +
> +	return drm_gem_prime_import_dev(dev, dma_buf, private->dma_dev);
> +}
> +

I think this part should be an independent patch which fixup
119f5173628aa ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")

Regards,
CK

>  static struct drm_driver mtk_drm_driver = {
>  	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_PRIME |
>  			   DRIVER_ATOMIC,
> @@ -331,7 +372,7 @@ static struct drm_driver mtk_drm_driver = {
>  	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>  	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>  	.gem_prime_export = drm_gem_prime_export,
> -	.gem_prime_import = drm_gem_prime_import,
> +	.gem_prime_import = mtk_drm_gem_prime_import,
>  	.gem_prime_get_sg_table = mtk_gem_prime_get_sg_table,
>  	.gem_prime_import_sg_table = mtk_gem_prime_import_sg_table,
>  	.gem_prime_mmap = mtk_drm_gem_mmap_buf,
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> index 598ff3e70446..e03fea12ff59 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> @@ -51,6 +51,8 @@ struct mtk_drm_private {
>  	} commit;
>  
>  	struct drm_atomic_state *suspend_state;
> +
> +	bool dma_parms_allocated;
>  };
>  
>  extern struct platform_driver mtk_ddp_driver;