Re: [PATCH] mtd: brcmnand: Disable prefetch by default

Boris Brezillon
2018-01-06T09:33:06Z

Hi Kamal,

The prefix should be "mtd: nand: brcmnand: ".

On Tue, 2 Jan 2018 15:14:57 -0500
Kamal Dasu <kdasu.kdev@gmail.com> wrote:

> Brcm nand controller prefetch feature needs to be disabled
> by default. Enabling effects performance on random reads as

^ affects ?

> well as dma reads.
>
> Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>

Maybe Fixes and CC-stable tags would be relevant here, unless you don't
consider this patch as a fix and don't want to backport it to stable
kernels.

> ---
> drivers/mtd/nand/brcmnand/brcmnand.c | 13 +++----------
> 1 file changed, 3 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
> index dd56a67..2a978d9 100644
> --- a/drivers/mtd/nand/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/brcmnand/brcmnand.c
> @@ -2193,16 +2193,9 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
> if (ctrl->nand_version >= 0x0702)
> tmp |= ACC_CONTROL_RD_ERASED;
> tmp &= ~ACC_CONTROL_FAST_PGM_RDIN;
> - if (ctrl->features & BRCMNAND_HAS_PREFETCH) {
> - /*
> - * FIXME: Flash DMA + prefetch may see spurious erased-page ECC
> - * errors
> - */
> - if (has_flash_dma(ctrl))
> - tmp &= ~ACC_CONTROL_PREFETCH;
> - else
> - tmp |= ACC_CONTROL_PREFETCH;
> - }
> + if (ctrl->features & BRCMNAND_HAS_PREFETCH)
> + tmp &= ~ACC_CONTROL_PREFETCH;
> +
> nand_writereg(ctrl, offs, tmp);
>
> return 0;