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authorben@fluff.org.uk <ben@fluff.org.uk>2008-10-14 23:17:18 (GMT)
committerPierre Ossman <drzeus@drzeus.cx>2008-10-15 16:05:48 (GMT)
commit18280fff663b8ba57e349a81b999604bc1106926 (patch)
tree4b81883aacc8de3f4febb6aae51b03e81c1b3156 /drivers/mmc
parent088a78af978d0c8e339071a9b2bca1f4cb368f30 (diff)
downloadlinux-18280fff663b8ba57e349a81b999604bc1106926.tar.xz
s3cmci: fix continual accesses to host->pio_ptr
The s3cmci driver uses the host->pio_ptr field to point to the current position into the buffer for data transfer. During the transfers it does the following: while (fifo_words--) *(host->pio_ptr++) = readl(from_ptr); This is inefficent, as host->pio_ptr is not used in any other part of the transfer but the compiler emits code which does the following: while (fifo_words--) { u32 *ptr = host->pio_ptr; *ptr = readl(from_ptr); ptr++; host->pio_ptr = ptr; } This is obviously a waste of a load and store each time around the loop, which could be up to 16 times depending on how much needs to be transfered. Move the ptr accesses to outside the while loop so that we do not end up reloading/re-writing the pointer. Note, this seems to make the code 16 bytes larger. Signed-off-by: Ben Dooks <ben-linux@fluff.org> Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
Diffstat (limited to 'drivers/mmc')
-rw-r--r--drivers/mmc/host/s3cmci.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/drivers/mmc/host/s3cmci.c b/drivers/mmc/host/s3cmci.c
index bb41233..5211d90 100644
--- a/drivers/mmc/host/s3cmci.c
+++ b/drivers/mmc/host/s3cmci.c
@@ -238,6 +238,7 @@ static void do_pio_read(struct s3cmci_host *host)
{
int res;
u32 fifo;
+ u32 *ptr;
u32 fifo_words;
void __iomem *from_ptr;
@@ -283,8 +284,10 @@ static void do_pio_read(struct s3cmci_host *host)
host->pio_count += fifo;
fifo_words = fifo >> 2;
+ ptr = host->pio_ptr;
while (fifo_words--)
- *(host->pio_ptr++) = readl(from_ptr);
+ *ptr++ = readl(from_ptr);
+ host->pio_ptr = ptr;
if (fifo & 3) {
u32 n = fifo & 3;
@@ -319,6 +322,7 @@ static void do_pio_write(struct s3cmci_host *host)
void __iomem *to_ptr;
int res;
u32 fifo;
+ u32 *ptr;
to_ptr = host->base + host->sdidata;
@@ -353,8 +357,10 @@ static void do_pio_write(struct s3cmci_host *host)
host->pio_count += fifo;
fifo = (fifo + 3) >> 2;
+ ptr = host->pio_ptr;
while (fifo--)
- writel(*(host->pio_ptr++), to_ptr);
+ writel(*ptr++, to_ptr);
+ host->pio_ptr = ptr;
}
enable_imask(host, S3C2410_SDIIMSK_TXFIFOHALF);