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Date: Sat, 6 Jan 2018 10:32:43 +0100
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Kamal Dasu <kdasu.kdev@gmail.com>
Cc: linux-mtd@lists.infradead.org, bcm-kernel-feedback-list@broadcom.com,
 richard@nod.at, marek.vasut@gmail.com, cyrille.pitchen@wedev4u.fr,
 computersforpeace@gmail.com, dwmw2@infradead.org
Subject: Re: [PATCH] mtd: brcmnand: Disable prefetch by default
Message-ID: <20180106103243.0ebf1561@bbrezillon>
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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;