linux-kernel - Re: [PATCH v2] xen: Stop abusing DT of_dma

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Message-ID: <alpine.DEB.2.21.1910101841380.9081@sstabellini-ThinkPad-T480s>
Date:   Thu, 10 Oct 2019 18:42:00 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Rob Herring <robh@...nel.org>
cc:     xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        Robin Murphy <robin.murphy@....com>,
        Julien Grall <julien.grall@....com>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] xen: Stop abusing DT of_dma_configure API

On Tue, 8 Oct 2019, Rob Herring wrote:
> As the removed comments say, these aren't DT based devices.
> of_dma_configure() is going to stop allowing a NULL DT node and calling
> it will no longer work.
> 
> The comment is also now out of date as of commit 9ab91e7c5c51 ("arm64:
> default to the direct mapping in get_arch_dma_ops"). Direct mapping
> is now the default rather than dma_dummy_ops.
> 
> According to Stefano and Oleksandr, the only other part needed is
> setting the DMA masks and there's no reason to restrict the masks to
> 32-bits. So set the masks to 64 bits.
> 
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Julien Grall <julien.grall@....com>
> Cc: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> Cc: Oleksandr Andrushchenko <oleksandr_andrushchenko@...m.com>
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Stefano Stabellini <sstabellini@...nel.org>
> Cc: Christoph Hellwig <hch@....de>
> Cc: xen-devel@...ts.xenproject.org
> Signed-off-by: Rob Herring <robh@...nel.org>

Reviewed-by: Stefano Stabellini <sstabellini@...nel.org>


> ---
> v2:
>  - Setup dma masks
>  - Also fix xen_drm_front.c
>  
> This can now be applied to the Xen tree independent of the coming
> of_dma_configure() changes.
> 
> Rob
> 
>  drivers/gpu/drm/xen/xen_drm_front.c | 12 ++----------
>  drivers/xen/gntdev.c                | 13 ++-----------
>  2 files changed, 4 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xen/xen_drm_front.c b/drivers/gpu/drm/xen/xen_drm_front.c
> index ba1828acd8c9..4be49c1aef51 100644
> --- a/drivers/gpu/drm/xen/xen_drm_front.c
> +++ b/drivers/gpu/drm/xen/xen_drm_front.c
> @@ -718,17 +718,9 @@ static int xen_drv_probe(struct xenbus_device *xb_dev,
>  	struct device *dev = &xb_dev->dev;
>  	int ret;
>  
> -	/*
> -	 * The device is not spawn from a device tree, so arch_setup_dma_ops
> -	 * is not called, thus leaving the device with dummy DMA ops.
> -	 * This makes the device return error on PRIME buffer import, which
> -	 * is not correct: to fix this call of_dma_configure() with a NULL
> -	 * node to set default DMA ops.
> -	 */
> -	dev->coherent_dma_mask = DMA_BIT_MASK(32);
> -	ret = of_dma_configure(dev, NULL, true);
> +	ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(64));
>  	if (ret < 0) {
> -		DRM_ERROR("Cannot setup DMA ops, ret %d", ret);
> +		DRM_ERROR("Cannot setup DMA mask, ret %d", ret);
>  		return ret;
>  	}
>  
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index a446a7221e13..81401f386c9c 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -22,6 +22,7 @@
>  
>  #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
>  
> +#include <linux/dma-mapping.h>
>  #include <linux/module.h>
>  #include <linux/kernel.h>
>  #include <linux/init.h>
> @@ -34,9 +35,6 @@
>  #include <linux/slab.h>
>  #include <linux/highmem.h>
>  #include <linux/refcount.h>
> -#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> -#include <linux/of_device.h>
> -#endif
>  
>  #include <xen/xen.h>
>  #include <xen/grant_table.h>
> @@ -625,14 +623,7 @@ static int gntdev_open(struct inode *inode, struct file *flip)
>  	flip->private_data = priv;
>  #ifdef CONFIG_XEN_GRANT_DMA_ALLOC
>  	priv->dma_dev = gntdev_miscdev.this_device;
> -
> -	/*
> -	 * The device is not spawn from a device tree, so arch_setup_dma_ops
> -	 * is not called, thus leaving the device with dummy DMA ops.
> -	 * Fix this by calling of_dma_configure() with a NULL node to set
> -	 * default DMA ops.
> -	 */
> -	of_dma_configure(priv->dma_dev, NULL, true);
> +	dma_coerce_mask_and_coherent(priv->dma_dev, DMA_BIT_MASK(64));
>  #endif
>  	pr_debug("priv %p\n", priv);
>  
> -- 
> 2.20.1
>