All of lore.kernel.org
 help / color / mirror / Atom feed
From: Wolfram Sang <wsa@the-dreams.de>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-renesas-soc@vger.kernel.org, linux-iio@vger.kernel.org,
	linux-input@vger.kernel.org, linux-media@vger.kernel.org,
	Mark Brown <broonie@kernel.org>
Subject: Re: [PATCH v6 0/9] i2c: document DMA handling and add helpers for it
Date: Mon, 4 Dec 2017 22:25:13 +0100	[thread overview]
Message-ID: <20171204212512.6aml52cmzbul423v@ninjato> (raw)
In-Reply-To: <20171104202009.3818-1-wsa+renesas@sang-engineering.com>

[-- Attachment #1: Type: text/plain, Size: 2134 bytes --]

On Sat, Nov 04, 2017 at 09:20:00PM +0100, Wolfram Sang wrote:
> So, after revisiting old mail threads, taking part in a similar discussion on
> the USB list, and implementing a not-convincing solution before, here is what I
> cooked up to document and ease DMA handling for I2C within Linux. Please have a
> look at the documentation introduced in patch 7 for details. And to make it
> clear again: The stuff below is opt-in. If host drivers are not updated, they
> will continue to work like before.
> 
> While previous versions until v3 tried to magically apply bounce buffers when
> needed, it became clear that detecting DMA safe buffers is too fragile. This
> approach is now opt-in, a DMA_SAFE flag needs to be set on an i2c_msg. The
> outcome so far is very convincing IMO. The core additions are simple and easy
> to understand. The driver changes for the Renesas IP cores became easy to
> understand, too.
> 
> Of course, we must now whitelist DMA safe buffers. This series implements it
> for core functionality:
> 
> a) for the I2C_RDWR when messages come from userspace
> b) for i2c_smbus_xfer_emulated(), DMA safe buffers are now allocated for
>    block transfers
> c) i2c_master_{send|recv} have now a *_dmasafe variant
> 
> I am still not sure how we can teach regmap this new flag. regmap is a heavy
> user of I2C, so broonie's opinion here would be great to have. The rest should
> mostly be updating individual drivers which can be done when needed.
> 
> All patches have been tested with a Renesas Salvator-X board (r8a7796/M3-W) and
> Renesas Lager board (r8a7790/H2). But more testing is really really welcome.
> 
> The branch can be found here:
> 
> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/topic/i2c-core-dma-v6
> 
> It is planned to land upstream in v4.16 and I want to push it to linux-next
> early after v4.15 to get lots of testing for the core changes.
> 
> Big kudos to Renesas Electronics for funding this work, thank you very much!
> 
> Regards,
> 
>    Wolfram

Applied to for-next after fixing some cosmetic checkpatch issues!


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]

      parent reply	other threads:[~2017-12-04 21:25 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-04 20:20 [PATCH v6 0/9] i2c: document DMA handling and add helpers for it Wolfram Sang
2017-11-04 20:20 ` Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 1/9] i2c: add a message flag for DMA safe buffers Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 2/9] i2c: add helpers to ease DMA handling Wolfram Sang
2017-11-04 20:20   ` Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 3/9] i2c: dev: mark RDWR buffers as DMA_SAFE Wolfram Sang
2017-11-04 20:20   ` Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 4/9] i2c: refactor i2c_master_{send_recv} Wolfram Sang
2017-11-11  0:03   ` Jonathan Cameron
2017-11-11  0:03     ` Jonathan Cameron
2017-11-04 20:20 ` [PATCH v6 5/9] i2c: add i2c_master_{send|recv}_dmasafe Wolfram Sang
2017-11-11  0:08   ` Jonathan Cameron
2017-11-11  0:08     ` Jonathan Cameron
2017-11-04 20:20 ` [PATCH v6 6/9] i2c: smbus: use DMA safe buffers for emulated SMBus transactions Wolfram Sang
2017-11-11  0:13   ` Jonathan Cameron
2017-11-11  0:13     ` Jonathan Cameron
2017-11-04 20:20 ` [PATCH v6 7/9] i2c: add docs to clarify DMA handling Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 8/9] i2c: sh_mobile: use core helper to decide when to use DMA Wolfram Sang
2017-11-04 20:20 ` [PATCH v6 9/9] i2c: rcar: skip DMA if buffer is not safe Wolfram Sang
2017-11-08 22:50 ` [PATCH v6 0/9] i2c: document DMA handling and add helpers for it Mark Brown
2017-11-27 18:51   ` Wolfram Sang
2017-11-28 15:34     ` Mark Brown
2017-12-03 19:43       ` Wolfram Sang
2017-12-04 22:05         ` Mark Brown
2017-12-04 22:05           ` Mark Brown
2017-12-05 11:00           ` Jonathan Cameron
2017-12-05 11:00             ` Jonathan Cameron
2017-12-04 21:25 ` Wolfram Sang [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=20171204212512.6aml52cmzbul423v@ninjato \
    --to=wsa@the-dreams.de \
    --cc=broonie@kernel.org \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-iio@vger.kernel.org \
    --cc=linux-input@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-renesas-soc@vger.kernel.org \
    --cc=wsa+renesas@sang-engineering.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.