On Tue, Aug 27, 2019 at 04:45:20PM +0900, Masahiro Yamada wrote:

On Mon, Aug 26, 2019 at 4:33 PM Christoph Hellwig [off-list ref] wrote:

quoted

On Mon, Aug 26, 2019 at 11:05:00AM +0900, Masahiro Yamada wrote:

quoted

This is included in v5.3-rc6
so I tested it.

So there is no allocation failure, but you get I/O errors later?

Right.

quoted

Does the device use a device-private CMA area?

Not sure.
My driver is drivers/mmc/host/sdhci-cadence.c
It reuses routines in drivers/mmc/host/sdhci.c

quoted

 Does it work with Linux
5.2 if CONFIG_DMA_CMA is disabled?

No.
5.2 + disable CONFIG_DMA_CMA
failed in the same way.

So it seems like the device wants CMA memory.   I guess the patch
below will fix it, but that isn't the solution.  Can you try it
to confirm?  In the end it probably assumes a dma mask it doesn't
set that the CMA memory satisfies or something similar.

diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
index 69cfb4345388..bd2f24aa7f19 100644
--- a/kernel/dma/contiguous.c
+++ b/kernel/dma/contiguous.c

@@ -236,7 +236,7 @@ struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)
 
 	if (dev && dev->cma_area)
 		cma = dev->cma_area;
-	else if (count > 1)
+	else
 		cma = dma_contiguous_default_area;
 
 	/* CMA can be used only in the context which permits sleeping */

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