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authorben@fluff.org.uk <ben@fluff.org.uk>2008-10-15 00:17:18 +0100
committerPierre Ossman <drzeus@drzeus.cx>2008-10-15 18:05:48 +0200
commit18280fff663b8ba57e349a81b999604bc1106926 (patch)
tree4b81883aacc8de3f4febb6aae51b03e81c1b3156
parent088a78af978d0c8e339071a9b2bca1f4cb368f30 (diff)
downloadlinux-18280fff663b8ba57e349a81b999604bc1106926.tar.bz2
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>
-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 bb412331e3d7..5211d90d34ef 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);