On 11/26/2012 04:33:08 AM, Phil Sutter wrote:
The basic idea is taken from the linux-kernel, but further optimized.
First align the buffer to 8 bytes, then use ldrd/strd to read and
store
in 8 byte quantities, then do the final bytes.
Tested using: 'date ; nand read.raw 0xE00000 0x0 0x10000 ; date'.
Without this patch, NAND read of 132MB took 49s (~2.69MB/s). With this
patch in place, reading the same amount of data was done in 27s
(~4.89MB/s). So read performance is increased by ~80%!
Signed-off-by: Nico Erfurth <n...@erfurth.eu>
Tested-by: Phil Sutter <phil.sut...@viprinet.com>
Cc: Prafulla Wadaskar <prafu...@marvell.com>
---
drivers/mtd/nand/kirkwood_nand.c | 29 +++++++++++++++++++++++++++++
1 files changed, 29 insertions(+), 0 deletions(-)
diff --git a/drivers/mtd/nand/kirkwood_nand.c
b/drivers/mtd/nand/kirkwood_nand.c
index bdab5aa..e04a59f 100644
--- a/drivers/mtd/nand/kirkwood_nand.c
+++ b/drivers/mtd/nand/kirkwood_nand.c
@@ -38,6 +38,34 @@ struct kwnandf_registers {
static struct kwnandf_registers *nf_reg =
(struct kwnandf_registers *)KW_NANDF_BASE;
+
+/* The basic idea is stolen from the linux kernel, but the inner
loop is optimized a bit more */
+static void kw_nand_read_buf(struct mtd_info *mtd, uint8_t *buf, int
len)
+{
+ struct nand_chip *chip = mtd->priv;
+
+ while (len && (unsigned long)buf & 7)
+ {
Brace goes on the previous line.
+ *buf++ = readb(chip->IO_ADDR_R);
+ len--;
+ };
+
+ asm volatile (
+ ".LFlashLoop:\n"
+ " subs\t%0, #8\n"
+ " ldrpld\tr2, [%2]\n" // Read 2 words
+ " strpld\tr2, [%1], #8\n" // Read 2 words
+ " bpl\t.LFlashLoop\n" // This results in one
additional loop if len%8 <> 0
+ " addne\t%0, #8\n"
+ : "+&r" (len), "+&r" (buf)
+ : "r" (chip->IO_ADDR_R)
+ : "r2", "r3", "memory", "cc"
+ );
Use a real tab (or a space) rather than \t (which only helps
readability in the asm output, rather than the C source that people
actually look at).
Should probably use a numeric label to avoid any possibility of
conflict.
Would this make more sense as a more generic optimized memcpy_fromio()
or similar?
-Scott
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