[U-Boot] [PATCHv2 1/4] Optimized nand_read_buf for kirkwood (V3)

[Scott Wood]

On Thu, Feb 21, 2013 at 06:21:53PM +0100, 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 <ne at erfurth.eu>
> Tested-by: Phil Sutter <phil.sutter at viprinet.com>
> Cc: Prafulla Wadaskar <prafulla at marvell.com>
> ---
>  drivers/mtd/nand/kirkwood_nand.c |   32 ++++++++++++++++++++++++++++++++
>  1 files changed, 32 insertions(+), 0 deletions(-)

Which is it, v2 or v3?

Patch versioning goes inside the [], otherwise "git am" won't strip it
out of the patch subject (and Wolfgang doesn't like patch subjects being
edited while being applied).

> diff --git a/drivers/mtd/nand/kirkwood_nand.c b/drivers/mtd/nand/kirkwood_nand.c
> index bdab5aa..99e5f35 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"
> +	);
> +
> +	while (len--)
> +		*buf++ = readb(chip->IO_ADDR_R);
> +}

Can someone ACK this from the ARM side?

-Scott