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From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Thomas Abraham <thomas.abraham@linaro.org>
Cc: Boojin Kim <boojin.kim@samsung.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org,
	Vinod Koul <vinod.koul@intel.com>,
	Dan Williams <dan.j.williams@intel.com>,
	Jassi Brar <jassisinghbrar@gmail.com>,
	Kukjin Kim <kgene.kim@samsung.com>,
	Mark Brown <broonie@opensource.wolfsonmicro.com>,
	Grant Likely <grant.likely@secretlab.ca>
Subject: Re: [PATCH 07/15] ARM: EXYNOS4: Use generic DMA PL330 driver
Date: Sun, 21 Aug 2011 09:51:08 +0100	[thread overview]
Message-ID: <20110821085108.GE12028@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAJuYYwT0R+VXWvWuV6KK=m_knoxBnBf=GLVimPoe002mcvqqeA@mail.gmail.com>

On Mon, Aug 15, 2011 at 07:45:48PM +0530, Thomas Abraham wrote:
> > +struct dma_pl330_peri pdma0_peri[28] = {
> > +       {
> > +               .peri_id = (u8)DMACH_PCM0_RX,
> > +               .rqtype = DEVTOMEM,
> > +       }, {
> 
> The client driver specifies the direction of the transfer
> (DMA_TO_DEVICE or DMA_FROM_DEVICE) when requesting for a dma channel.
> So, is the rqtype parameter required in the platform data for the dma
> driver?

That was done initially too with PL080, which has 8 uncommitted DMA
channels.  Peripheral drivers still had to pass the DMA direction.  So
it turned out to be entirely redundant information, so it got killed off,
along with other channel specific configuration which drivers should've
been doing via the slave configuration callback.

Passing lots of information via platform data which should come via
other routes makes dmaengine users fragile - you can't tell whether
they are passing the correct and full information necessary to work with
other dmaengine drivers.  So, the DMA engine platform data should only
contain the absolute _minimum_ of information.

WARNING: multiple messages have this Message-ID (diff)
From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 07/15] ARM: EXYNOS4: Use generic DMA PL330 driver
Date: Sun, 21 Aug 2011 09:51:08 +0100	[thread overview]
Message-ID: <20110821085108.GE12028@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <CAJuYYwT0R+VXWvWuV6KK=m_knoxBnBf=GLVimPoe002mcvqqeA@mail.gmail.com>

On Mon, Aug 15, 2011 at 07:45:48PM +0530, Thomas Abraham wrote:
> > +struct dma_pl330_peri pdma0_peri[28] = {
> > + ? ? ? {
> > + ? ? ? ? ? ? ? .peri_id = (u8)DMACH_PCM0_RX,
> > + ? ? ? ? ? ? ? .rqtype = DEVTOMEM,
> > + ? ? ? }, {
> 
> The client driver specifies the direction of the transfer
> (DMA_TO_DEVICE or DMA_FROM_DEVICE) when requesting for a dma channel.
> So, is the rqtype parameter required in the platform data for the dma
> driver?

That was done initially too with PL080, which has 8 uncommitted DMA
channels.  Peripheral drivers still had to pass the DMA direction.  So
it turned out to be entirely redundant information, so it got killed off,
along with other channel specific configuration which drivers should've
been doing via the slave configuration callback.

Passing lots of information via platform data which should come via
other routes makes dmaengine users fragile - you can't tell whether
they are passing the correct and full information necessary to work with
other dmaengine drivers.  So, the DMA engine platform data should only
contain the absolute _minimum_ of information.

  reply	other threads:[~2011-08-21  8:51 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-07-27  5:31 [PATCH V5 00/15] To use DMA generic APIs for Samsung DMA Boojin Kim
2011-07-27  5:31 ` Boojin Kim
2011-07-27  5:31 ` [PATCH 01/15] DMA: PL330: Add support runtime PM for PL330 DMAC Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  6:14   ` [RFC PATCH] DMA: PL330: Update PL330 DMAC to support runtime PM Chanwoo Choi
2011-07-27  6:14     ` Chanwoo Choi
2011-07-27  7:31     ` Jassi Brar
2011-07-27  7:31       ` Jassi Brar
2011-07-27  8:53     ` Russell King - ARM Linux
2011-07-27  8:53       ` Russell King - ARM Linux
2011-07-27  9:43       ` Chanwoo Choi
2011-07-27  9:43         ` Chanwoo Choi
2011-07-27  7:43   ` [PATCH 01/15] DMA: PL330: Add support runtime PM for PL330 DMAC Jassi Brar
2011-07-27  7:43     ` Jassi Brar
2011-07-27  5:31 ` [PATCH 02/15] DMA: PL330: Update PL330 DMA API driver Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 03/15] DMA: PL330: Support DMA_SLAVE_CONFIG command Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 04/15] DMA: PL330: Add DMA_CYCLIC capability Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 05/15] ARM: SAMSUNG: Update to use PL330-DMA driver Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 06/15] ARM: SAMSUNG: Add common DMA operations Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 07/15] ARM: EXYNOS4: Use generic DMA PL330 driver Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-08-15  9:36   ` Thomas Abraham
2011-08-15  9:36     ` Thomas Abraham
2011-08-15 14:15   ` Thomas Abraham
2011-08-15 14:15     ` Thomas Abraham
2011-08-21  8:51     ` Russell King - ARM Linux [this message]
2011-08-21  8:51       ` Russell King - ARM Linux
2011-07-27  5:31 ` [PATCH 08/15] ARM: S5PV210: " Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 09/15] ARM: S5PC100: " Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 10/15] ARM: S5P64X0: " Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 11/15] ARM: SAMSUNG: Remove S3C-PL330-DMA driver Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-07-27  5:31 ` [PATCH 12/15] spi/s3c64xx: Add support DMA engine API Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-08-08 17:47   ` Jassi Brar
2011-08-08 17:47     ` Jassi Brar
2011-08-08 17:55     ` Heiko Stübner
2011-08-08 17:55       ` Heiko Stübner
2011-08-08 18:16       ` Jassi Brar
2011-08-08 18:16         ` Jassi Brar
2011-08-08 18:26         ` Heiko Stübner
2011-08-08 18:26           ` Heiko Stübner
2011-08-09  4:13     ` Alim Akhtar
2011-08-09  4:13       ` Alim Akhtar
2011-08-19 10:30       ` Alim Akhtar
2011-08-19 10:30         ` Alim Akhtar
2011-08-21  8:46       ` Russell King - ARM Linux
2011-08-21  8:46         ` Russell King - ARM Linux
2011-08-25  1:13         ` Alim Akhtar
2011-08-25  1:13           ` Alim Akhtar
2011-08-11  7:42     ` Boojin Kim
2011-08-11  7:42       ` Boojin Kim
2011-07-27  5:31 ` [PATCH 13/15] spi/s3c64xx: Merge dma control code Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-08-08 18:32   ` Jassi Brar
2011-08-08 18:32     ` Jassi Brar
2011-07-27  5:31 ` [PATCH 14/15] ASoC: Samsung: Update DMA interface Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-08-08 19:27   ` Jassi Brar
2011-08-08 19:27     ` Jassi Brar
2011-08-11 10:04     ` Boojin Kim
2011-08-11 10:04       ` Boojin Kim
2011-07-27  5:31 ` [PATCH 15/15] ARM: SAMSUNG: Remove Samsung specific enum type for dma direction Boojin Kim
2011-07-27  5:31   ` Boojin Kim
2011-08-04 16:53 ` [PATCH V5 00/15] To use DMA generic APIs for Samsung DMA Linus Walleij
2011-08-04 16:53   ` Linus Walleij
2011-08-08 16:45   ` Koul, Vinod
2011-08-08 16:45     ` Koul, Vinod
2011-08-11  7:26     ` Kukjin Kim
2011-08-11  7:26       ` Kukjin Kim
2011-08-11 22:27       ` Koul, Vinod
2011-08-11 22:27         ` Koul, Vinod
2011-08-13  4:11         ` Kukjin Kim
2011-08-13  4:11           ` Kukjin Kim
2011-08-16 11:01           ` Koul, Vinod
2011-08-16 11:01             ` Koul, Vinod
2011-08-19  5:24             ` Kukjin Kim
2011-08-19  5:24               ` Kukjin Kim
2011-08-19 13:04               ` Koul, Vinod
2011-08-19 13:04                 ` Koul, Vinod

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