OF: Don't set default coherent DMA mask

Now that we can track upstream DMA constraints properly with
bus_dma_mask instead of trying (and failing) to maintain it in
coherent_dma_mask, it doesn't make much sense for the firmware code to
be touching the latter at all. It's merely papering over bugs wherein a
driver has failed to call dma_set_coherent_mask() *and* the bus code has
not initialised any default value.

We don't really want to encourage more drivers coercing dma_mask so
we'll continue to fix that up if necessary, but add a warning to help
flush out any such buggy bus code that remains.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 10 insertions, 10 deletions

diff --git a/drivers/of/device.c b/drivers/of/device.c
index 0d39633e8545..5957cd4fa262 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -127,20 +127,20 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
         }
 
         /*
-         * Set default coherent_dma_mask to 32 bit.  Drivers are expected to
-         * setup the correct supported mask.
+         * If @dev is expected to be DMA-capable then the bus code that created
+         * it should have initialised its dma_mask pointer by this point. For
+         * now, we'll continue the legacy behaviour of coercing it to the
+         * coherent mask if not, but we'll no longer do so quietly.
          */
-        if (!dev->coherent_dma_mask)
-                dev->coherent_dma_mask = DMA_BIT_MASK(32);
-        /*
-         * Set it to coherent_dma_mask by default if the architecture
-         * code has not set it.
-         */
-        if (!dev->dma_mask)
+        if (!dev->dma_mask) {
+                dev_warn(dev, "DMA mask not set\n");
                 dev->dma_mask = &dev->coherent_dma_mask;
+        }
 
-        if (!size)
+        if (!size && dev->coherent_dma_mask)
                 size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1);
+        else if (!size)
+                size = 1ULL << 32;
 
         dev->dma_pfn_offset = offset;