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From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: Mark Brown <broonie@kernel.org>
Cc: Wolfram Sang <wsa@the-dreams.de>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	<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>
Subject: Re: [PATCH v6 0/9] i2c: document DMA handling and add helpers for it
Date: Tue, 5 Dec 2017 11:00:05 +0000	[thread overview]
Message-ID: <20171205110005.00004d66@huawei.com> (raw)
In-Reply-To: <20171204220541.GA11658@finisterre>

On Mon, 4 Dec 2017 22:05:41 +0000
Mark Brown <broonie@kernel.org> wrote:

> On Sun, Dec 03, 2017 at 08:43:47PM +0100, Wolfram Sang wrote:
> 
> > > It's a bit different in that it's much more likely that a SPI controller
> > > will actually do DMA than an I2C one since the speeds are higher and
> > > there's frequent applications that do large transfers so it's more
> > > likely that people will do the right thing as issues would tend to come
> > > up if they don't.  
> 
> > Yes, for SPI this is true. I was thinking more of regmap with its
> > usage of different transport mechanisms. But I guess they should all be
> > DMA safe because some of them need to be DMA safe?  
> 
> Possibly.  Hopefully.  I guess we'll find out.
> 

Yeah, optimistic assumption. Plenty of drivers use regmap for the
convenience of it's caching and field access etc rather than
because they support multiple buses.

I'll audit the IIO drivers and see where we have issues if we
start assuming DMA safe for regmap (which makes sense to me).

Probably worth fixing them all up anyway and tends to be straightforward.

Jonathan

WARNING: multiple messages have this Message-ID (diff)
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
To: Mark Brown <broonie@kernel.org>
Cc: Wolfram Sang <wsa@the-dreams.de>,
	Wolfram Sang <wsa+renesas@sang-engineering.com>,
	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
Subject: Re: [PATCH v6 0/9] i2c: document DMA handling and add helpers for it
Date: Tue, 5 Dec 2017 11:00:05 +0000	[thread overview]
Message-ID: <20171205110005.00004d66@huawei.com> (raw)
In-Reply-To: <20171204220541.GA11658@finisterre>

On Mon, 4 Dec 2017 22:05:41 +0000
Mark Brown <broonie@kernel.org> wrote:

> On Sun, Dec 03, 2017 at 08:43:47PM +0100, Wolfram Sang wrote:
> 
> > > It's a bit different in that it's much more likely that a SPI controller
> > > will actually do DMA than an I2C one since the speeds are higher and
> > > there's frequent applications that do large transfers so it's more
> > > likely that people will do the right thing as issues would tend to come
> > > up if they don't.  
> 
> > Yes, for SPI this is true. I was thinking more of regmap with its
> > usage of different transport mechanisms. But I guess they should all be
> > DMA safe because some of them need to be DMA safe?  
> 
> Possibly.  Hopefully.  I guess we'll find out.
> 

Yeah, optimistic assumption. Plenty of drivers use regmap for the
convenience of it's caching and field access etc rather than
because they support multiple buses.

I'll audit the IIO drivers and see where we have issues if we
start assuming DMA safe for regmap (which makes sense to me).

Probably worth fixing them all up anyway and tends to be straightforward.

Jonathan

  reply	other threads:[~2017-12-05 11:00 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 [this message]
2017-12-05 11:00             ` Jonathan Cameron
2017-12-04 21:25 ` Wolfram Sang

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