From 18280fff663b8ba57e349a81b999604bc1106926 Mon Sep 17 00:00:00 2001 From: "ben@fluff.org.uk" Date: Wed, 15 Oct 2008 00:17:18 +0100 Subject: [PATCH] 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 Signed-off-by: Pierre Ossman --- drivers/mmc/host/s3cmci.c | 10 ++++++++-- 1 file 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); -- 2.34.1