On 09/25/13 14:01, Jayachandran C wrote:
The check cpu_needs_post_dma_flush() in mips_dma_sync_sg_for_cpu() and
the check !plat_device_is_coherent() in mips_dma_sync_sg_for_device()
can be moved outside the for loop.
As a side effect, this also avoids a GCC bug that caused kernel compile
to fail with the error:
arch/mips/mm/dma-default.c: In function 'mips_dma_sync_sg_for_cpu':
arch/mips/mm/dma-default.c:316:1: internal compiler error: in add_insn_before, at emit-rtl.c:3852
This gcc failure is seen in Code Sourcery toolchains [e.g. gcc version
4.7.2 (Sourcery CodeBench Lite 2012.09-99)] after commit "MIPS: Optimize
current_cpu_type() for better code."
---
arch/mips/mm/dma-default.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)
diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index e45e4b0..2e94185 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -307,12 +307,10 @@ static void mips_dma_sync_sg_for_cpu(struct device *dev,
{
int i;
- /* Make sure that gcc doesn't leave the empty loop body. */
- for (i = 0; i < nelems; i++, sg++) {
- if (cpu_needs_post_dma_flush(dev))
+ if (cpu_needs_post_dma_flush(dev))
+ for (i = 0; i < nelems; i++, sg++)
__dma_sync(sg_page(sg), sg->offset, sg->length,
direction);
- }
}
static void mips_dma_sync_sg_for_device(struct device *dev,
@@ -320,12 +318,10 @@ static void mips_dma_sync_sg_for_device(struct device *dev,
{
int i;
- /* Make sure that gcc doesn't leave the empty loop body. */
- for (i = 0; i < nelems; i++, sg++) {
- if (!plat_device_is_coherent(dev))
+ if (!plat_device_is_coherent(dev))
+ for (i = 0; i < nelems; i++, sg++)
__dma_sync(sg_page(sg), sg->offset, sg->length,
direction);
- }
}
int mips_dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
Hi,
The patch looks good to me and it fixes the gcc problem indeed (the bug
is also present in gcc-4.7.3 from the 2013.05 release)
Reviewed-by/Tested-by: Markos Chandras <markos.chandras@xxxxxxxxxx>
