drm/etnaviv: use a 32 bit mask as coherent DMA mask

The STLB and the first command buffer (which is used to set up the TLBs)
has a 32 bit size restriction in hardware. There seems to be no way to
specify addresses larger than 32 bit. Keep it simple and restict the
addresses to the lower 4 GiB range for all coherent DMA memory
allocations.

Please note, that platform_device_alloc() will initialize dev->dma_mask
to point to pdev->platform_dma_mask, thus dma_set_mask() will work as
expected.

While at it, move the dma_mask setup code to the of_dma_configure() to
keep all the DMA setup code next to each other.

Suggested-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
(cherry picked from commit 4a4a708db17d9a622fee339c6bb6c95e324d4cf0)
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
index aa270b79e58558a79358d11937791b8e96c998c8..17f416c0465efe8802038207510deb7e3422cf2a 100644 (file)
--- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
@@ -672,8 +672,24 @@ static int __init etnaviv_init(void)
                        of_node_put(np);
                        goto unregister_platform_driver;
                }
-               pdev->dev.coherent_dma_mask = DMA_BIT_MASK(40);
-               pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask;
+
+               /*
+                * PTA and MTLB can have 40 bit base addresses, but
+                * unfortunately, an entry in the MTLB can only point to a
+                * 32 bit base address of a STLB. Moreover, to initialize the
+                * MMU we need a command buffer with a 32 bit address because
+                * without an MMU there is only an indentity mapping between
+                * the internal 32 bit addresses and the bus addresses.
+                *
+                * To make things easy, we set the dma_coherent_mask to 32
+                * bit to make sure we are allocating the command buffers and
+                * TLBs in the lower 4 GiB address space.
+                */
+               if (dma_set_mask(&pdev->dev, DMA_BIT_MASK(40)) ||
+                   dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32))) {
+                       dev_dbg(&pdev->dev, "No suitable DMA available\n");
+                       return -ENODEV;
+               }
 
                /*
                 * Apply the same DMA configuration to the virtual etnaviv