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Date: Sun, 8 May 2016 18:44:51 +0200
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Iwo Mergler <iwo.mergler@netcommwireless.com>
Cc: <linux-mtd@lists.infradead.org>, Richard Weinberger <richard@nod.at>,
 Brian Norris <computersforpeace@gmail.com>, Huang Shijie
 <b32955@freescale.com>
Subject: Re: [PATCH] mtd: nandbiterrs: Support for NAND biterrors test on
 platforms without raw write
Message-ID: <20160508184451.3d90176a@bbrezillon>
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Hi Iwo,

On Fri, 6 May 2016 10:00:12 +1000
Iwo Mergler <iwo.mergler@netcommwireless.com> wrote:

> Hi all,
> 
> 
> I'm vaguely aware that there is an ongoing effort to move this
> stuff to mtd-utils, but I was unable to find a source tree
> with the work so far.
> 
> Below is a single-line patch for the kernel tests, feel free
> to apply to the userspace source as well.
> 
> 
> Best regards,
> 
> Iwo
> 
> 
> Support for NAND biterrors test on platforms without raw write
> 
> While the default test mode relies on raw write (mtd_write_oob) to introduce
> bit errors into a page, the rewrite test mode doesn't need it.
> 
> Some drivers use eldritch data/ECC arrangements in a NAND page and reshuffle
> things on-the-fly, to present a normal page view to the kernel. Typically,
> raw write / read is unsupported on such platforms. Examples are Freescale
> MXS and Qualcomm MDM9 and probably many others.

Sorry, but I think such platforms should unshuffle the data/ECC
sections to expose a standard in-band/out-of-band view to the upper
layer.

This is completely doable since ->read_page_raw()/->write_page_raw()
can be overloaded (see the GPMI implementation or the default
ECC_HW_SYNDROME raw implementation if you need examples).

So, it's a NACK on my side.

Best Regards,

Boris


> 
> Changed the overwrite test to use normal writes.
> 
> Signed-off-by: Iwo Mergler <Iwo.Mergler@netcommwireless.com>
> ---
>   drivers/mtd/tests/nandbiterrs.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/tests/nandbiterrs.c 
> b/drivers/mtd/tests/nandbiterrs.c
> index 09a4cca..f26dec8 100644
> --- a/drivers/mtd/tests/nandbiterrs.c
> +++ b/drivers/mtd/tests/nandbiterrs.c
> @@ -290,7 +290,7 @@ static int overwrite_test(void)
> 
>       while (opno < max_overwrite) {
> 
> -        err = rewrite_page(0);
> +        err = write_page(0);
>           if (err)
>               break;
> 



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com