xen: Stop abusing DT of_dma_configure API

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The comment is also now out of date as of commit 9ab91e7c5c51 ("arm64: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 <[e-mail]>
Cc: Julien Grall <[e-mail]>
Cc: Nicolas Saenz Julienne <[e-mail]>
Cc: Oleksandr Andrushchenko <[e-mail]>
Cc: Boris Ostrovsky <[e-mail]>
Cc: Juergen Gross <[e-mail]>
Cc: Stefano Stabellini <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: [e-mail]
Signed-off-by: Rob Herring <[e-mail]>
Acked-by: Oleksandr Andrushchenko <[e-mail]>
Reviewed-by: Boris Ostrovsky <[e-mail]>
Signed-off-by: Boris Ostrovsky <[e-mail]>

drivers/gpu/drm/xen/xen_drm_front.c

···
 	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;
 	}
 

drivers/xen/gntdev.c

···
 
 #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>
···
 #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>
···
 	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);