From: "Hattink, Tjalling [FINT]" <T.Hattink@fugro.nl>
To: barebox@lists.infradead.org
Subject: RE: [PATCH] mtd: nand: disable subpage reads
Date: Mon, 3 Mar 2014 09:15:36 +0100 [thread overview]
Message-ID: <C89EFD3CD56F64468D3D206D683A8D220304224D@ldam-msx2.fugro-nl.local> (raw)
In-Reply-To: <1393833013-7783-1-git-send-email-s.hauer@pengutronix.de>
> -----Original Message-----
> From: Sascha Hauer [mailto:s.hauer@pengutronix.de]
> Sent: Monday, March 03, 2014 08:50
> To: barebox@lists.infradead.org
> Cc: Sascha Hauer; Hattink, Tjalling [FINT]
> Subject: [PATCH] mtd: nand: disable subpage reads
>
> The default nand_read_subpage implementation returns -ENOSUPP, so we
> have to make sure that barebox never uses this implementation. By
> setting the NAND_SUBPAGE_READ flag to 0x0 we ensure
> NAND_HAS_SUBPAGE_READ() never returns true and also give the compiler
a
> chance to optimize away some unused code.
>
> subpage reads are a rather exotic feature even in Linux. It is only
> used on largepage NANDs with soft ecc. Even if we have this case it
> needs non page aligned reads to actually profit from this feature.
>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: Hattink, Tjalling [FINT] <T.Hattink@fugro.nl>
> ---
>
> Hi Tjalling,
> I had a closer look at the subpage read stuff and saw that this is
> really an exotic feature that even if we could support it doesn't help
> very much. So I decided to go back to a variant of your first
> patch: Fix subpage reads by disabling them completely.
>
>
> include/linux/mtd/nand.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h index
> 74ea0b4..3c7509f 100644
> --- a/include/linux/mtd/nand.h
> +++ b/include/linux/mtd/nand.h
> @@ -162,7 +162,8 @@ typedef enum {
> #define NAND_ROM 0x00000800
>
> /* Device supports subpage reads */
> -#define NAND_SUBPAGE_READ 0x00001000
> +/* Disabled in barebox for smaller binary sizes */
> +#define NAND_SUBPAGE_READ (__BAREBOX__ ? 0x0 : 0x00001000)
>
> /* Options valid for Samsung large page devices */ #define
> NAND_SAMSUNG_LP_OPTIONS NAND_CACHEPRG
> --
> 1.8.5.3
Hi Sascha,
I don't think it matters much either when subpage read is disabled.
Barebox will not do heavy read operations on the nand so the subpage
support will not do much.
Thanks for resolving this bug,
Tjalling
_______________________________________________
barebox mailing list
barebox@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/barebox
prev parent reply other threads:[~2014-03-03 8:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-03-03 7:50 Sascha Hauer
2014-03-03 8:15 ` Hattink, Tjalling [FINT] [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=C89EFD3CD56F64468D3D206D683A8D220304224D@ldam-msx2.fugro-nl.local \
--to=t.hattink@fugro.nl \
--cc=barebox@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox