drm/simpledrm: Set DMA and coherency mask

Simpledrm is "DMA" access is not limited. All CPU addressible memory
can be used via direct DMA mappings.

Fixes following warning on Apple silicon systems. Physical memory on
those systems starts at (1 << 35) or (1 << 40) so 32-bit direct DMA
mappings are not possible.
------------[ cut here ]------------
simple-framebuffer 9e5064000.framebuffer: swiotlb addr 0x00000009de654000+16384 overflow (mask ffffffff, bus limit 0).
WARNING: CPU: 3 PID: 961 at kernel/dma/swiotlb.c:928 swiotlb_map+0x1f4/0x2a0
Modules linked in: ...
CPU: 3 PID: 961 Comm: kwin_wayland Not tainted 6.5.0-asahi+ #1
Hardware name: Apple Mac mini (M2, 2023) (DT)
...
Call trace:
 swiotlb_map+0x1f4/0x2a0
 dma_direct_map_sg+0x8c/0x2a8
 dma_map_sgtable+0x5c/0xd0
 drm_gem_map_dma_buf+0x64/0xb8
 dma_buf_map_attachment+0xac/0x158
 dma_buf_map_attachment_unlocked+0x48/0x80
 drm_gem_prime_import_dev+0xa0/0x1a0
 drm_gem_prime_fd_to_handle+0xc8/0x218
 drm_prime_fd_to_handle_ioctl+0x34/0x50
 drm_ioctl_kernel+0xe4/0x160
 drm_ioctl+0x23c/0x3e0
...
---[ end trace 0000000000000000 ]---

Avoids using swiotbl bounce buffers on other platforms when the mapped
memory is above 4GB.

Fixes: 11e8f5f ("drm: Add simpledrm driver")
Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/tiny/simpledrm.c

@@ -1029,6 +1029,12 @@ static int simpledrm_probe(struct platform_device *pdev)
 	unsigned int color_mode;
 	int ret;
 
+	ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
+	if (ret)
+		ret = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
+	if (ret)
+		return dev_err_probe(&pdev->dev, ret, "Failed to set dma mask\n");
+
 	sdev = simpledrm_device_create(&simpledrm_driver, pdev);
 	if (IS_ERR(sdev))
 		return PTR_ERR(sdev);