Hi Phil,
On Wed, 26 Jun 2013 20:25:25 +0200, Phil Sutter
<phil.sut...@viprinet.com> 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>
> ---
Patch history missing.
> drivers/mtd/nand/kirkwood_nand.c | 32 ++++++++++++++++++++++++++++++++
> 1 file changed, 32 insertions(+)
>
> diff --git a/drivers/mtd/nand/kirkwood_nand.c
> b/drivers/mtd/nand/kirkwood_nand.c
> index 0a99a10..85ea5d2 100644
> --- a/drivers/mtd/nand/kirkwood_nand.c
> +++ b/drivers/mtd/nand/kirkwood_nand.c
> @@ -38,6 +38,37 @@ 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) {
> + *buf++ = readb(chip->IO_ADDR_R);
> + len--;
> + };
> +
> + /* This loop reads and writes 64bit per round. */
> + asm volatile (
> + "1:\n"
> + " subs %0, #8\n"
> + " ldrpld r2, [%2]\n"
> + " strpld r2, [%1], #8\n"
> + " bhi 1b\n"
> + " addne %0, #8\n"
> + : "+&r" (len), "+&r" (buf)
> + : "r" (chip->IO_ADDR_R)
> + : "r2", "r3", "memory", "cc"
> + );
Are assembler instructions *really* required? IOW, can you not get
enough performance simply with a cleverly written C loop?
> + while (len--)
> + *buf++ = readb(chip->IO_ADDR_R);
> +}
> +
> /*
> * hardware specific access to control-lines/bits
> */
> @@ -80,6 +111,7 @@ int board_nand_init(struct nand_chip *nand)
> nand->ecc.mode = NAND_ECC_SOFT;
> #endif
> nand->cmd_ctrl = kw_nand_hwcontrol;
> + nand->read_buf = kw_nand_read_buf;
> nand->chip_delay = 40;
> nand->select_chip = kw_nand_select_chip;
> return 0;
Amicalement,
--
Albert.
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