From: nicolas.ferre@atmel•com (Nicolas Ferre)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH] MTD: atmel_nand: optimize read/write buffer functions
Date: Mon, 04 Jul 2011 15:02:47 +0200 [thread overview]
Message-ID: <4E11B9F7.5080606@atmel.com> (raw)
In-Reply-To: <20110629133124.GO21898@n2100.arm.linux.org.uk>
Le 29/06/2011 15:31, Russell King - ARM Linux :
> On Wed, Jun 29, 2011 at 03:09:59PM +0200, Nicolas Ferre wrote:
>> Le 28/06/2011 16:59, Russell King - ARM Linux :
>>> I think you need to read Documentation/bus-virt-phys-mapping.txt,
>>> particularly the part after "NOTE NOTE NOTE".
>>>
>>> Dereferencing ioremap'd memory is not permitted. That includes passing
>>> it to memcpy. Even with a cast.
>>
>> So that means that I should use memcpy_fromio() even if the code if far
>> less optimized.
>>
>> Shouldn't I re-implement some kind of IO copying function to deal with
>> this IO memory so that I could take advantage of 8 words bursts?
>
> You could improve the IO memcpy/set etc implementations, which are
> currently mostly unloved - I think that's a catch-22 which really needs
> solving. They're not efficient because no one has taken the time to use
> them, and everyone's avoiding them because they're not very efficient.
> So, as no one's using them no one's motivated to improve them.
Ok, so I use them in my following patch.
And as a long-term exercise, I will try to have a look at those IO
memcpy/set functions for ARM...
Thanks for you advices, best regards,
--
Nicolas Ferre
next prev parent reply other threads:[~2011-07-04 13:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-28 11:50 [RFC PATCH] MTD: atmel_nand: optimize read/write buffer functions Nicolas Ferre
2011-06-28 11:10 ` Uwe Kleine-König
2011-06-28 13:58 ` Nicolas Ferre
2011-06-28 14:59 ` Russell King - ARM Linux
2011-06-29 13:09 ` Nicolas Ferre
2011-06-29 13:31 ` Russell King - ARM Linux
2011-07-04 13:02 ` Nicolas Ferre [this message]
2011-07-04 14:17 ` [PATCH V2] " Nicolas Ferre
2011-07-06 6:58 ` Artem Bityutskiy
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=4E11B9F7.5080606@atmel.com \
--to=nicolas.ferre@atmel$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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