[PATCH] dmaengine: pl330: Fix linker error "undefined reference to `__aeabi_uldivmod'"

Jon Medhurst (Tixy) tixy at linaro.org
Thu Nov 13 08:27:27 PST 2014

32-bit ARM kernels may have a 64-bit dma_addr_t but have no
implementation of the compiler helper for 64-bit unsigned division,
therefore the use of the modulo operator in pl330_prep_dma_memcpy causes
the link error "undefined reference to `__aeabi_uldivmod'"

As the burst value is always a power of two we can fix the problem, and
make the code more efficient, by replacing "% burst" with "& (burst-1)".

Reported-by: kbuild test robot <fengguang.wu at intel.com>
Signed-off-by: Jon Medhurst <tixy at linaro.org>

Vinod. I haven't added a 'Fixes:' line because I was unsure if the patch
in linux-next is part of a stable branch or if the SHA1 might change
before hitting mainline. If it stable then the line should be...

Fixes: 63369d0a96dc ("dmaengine: pl330: Align DMA memcpy operations to MFIFO width")

 drivers/dma/pl330.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 38c9617..52c4c62 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2464,11 +2464,8 @@ pl330_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dst,
 	 * parameters because our DMA programming algorithm doesn't cope with
 	 * transfers which straddle an entry in the DMA device's MFIFO.
-	while (burst > 1) {
-		if (!((src | dst | len) % burst))
-			break;
+	while ((src | dst | len) & (burst - 1))
 		burst /= 2;
-	}
 	desc->rqcfg.brst_size = 0;
 	while (burst != (1 << desc->rqcfg.brst_size))

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