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From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Rob Herring <robherring2@gmail.com>
Cc: Thomas Abraham <thomas.abraham@linaro.org>,
	boojin.kim@samsung.com, kgene.kim@samsung.com,
	patches@linaro.org, vinod.koul@intel.com,
	devicetree-discuss@lists.ozlabs.org, jassisinghbrar@gmail.com,
	linux-samsung-soc@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 4/6] DMA: PL330: Add device tree support
Date: Fri, 26 Aug 2011 15:23:05 +0100	[thread overview]
Message-ID: <20110826142305.GA23469@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <4E579C9B.7030807@gmail.com>

On Fri, Aug 26, 2011 at 08:16:11AM -0500, Rob Herring wrote:
> Thomas,
> 
> On 08/26/2011 03:40 AM, Thomas Abraham wrote:
> > +  - arm,pl330-peri-reqs: number of actual peripheral requests connected to the
> > +    dma controller. Maximum value is 32.
> 
> Perhaps could be a bitmask for sparsely populated requests. May not
> matter since phandles will define the connections.
> 
> Can be optional and not present means 00 requests (mem-to-mem only).

The number of peripheral requests is readable from configuration register
zero, so this is discoverable.  Why should we put this information into
DT if its provided by the hardware?

The number of DMA channels available is also configurable by the SoC
designer, yet you don't specify that in DT.  And there's a whole bunch
of other configuration options available to the SoC designer, most of
which are discoverable from the configuration registers.

So, I don't think you should be specifying the number of requests.

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 4/6] DMA: PL330: Add device tree support
Date: Fri, 26 Aug 2011 15:23:05 +0100	[thread overview]
Message-ID: <20110826142305.GA23469@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <4E579C9B.7030807@gmail.com>

On Fri, Aug 26, 2011 at 08:16:11AM -0500, Rob Herring wrote:
> Thomas,
> 
> On 08/26/2011 03:40 AM, Thomas Abraham wrote:
> > +  - arm,pl330-peri-reqs: number of actual peripheral requests connected to the
> > +    dma controller. Maximum value is 32.
> 
> Perhaps could be a bitmask for sparsely populated requests. May not
> matter since phandles will define the connections.
> 
> Can be optional and not present means 00 requests (mem-to-mem only).

The number of peripheral requests is readable from configuration register
zero, so this is discoverable.  Why should we put this information into
DT if its provided by the hardware?

The number of DMA channels available is also configurable by the SoC
designer, yet you don't specify that in DT.  And there's a whole bunch
of other configuration options available to the SoC designer, most of
which are discoverable from the configuration registers.

So, I don't think you should be specifying the number of requests.

  reply	other threads:[~2011-08-26 14:23 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-26  8:40 [PATCH 0/6] Add device tree support for PL330 dma controller driver Thomas Abraham
2011-08-26  8:40 ` Thomas Abraham
2011-08-26  8:40 ` [PATCH 1/6] DMA: PL330: move filter function into driver Thomas Abraham
2011-08-26  8:40   ` Thomas Abraham
2011-08-26  8:40   ` [PATCH 2/6] DMA: PL330: Infer transfer direction from transfer request instead of platform data Thomas Abraham
2011-08-26  8:40     ` Thomas Abraham
2011-08-26  8:40     ` [PATCH 3/6] ARM: EXYNOS4: Modify platform data for pl330 driver Thomas Abraham
2011-08-26  8:40       ` Thomas Abraham
2011-08-26  8:40       ` [PATCH 4/6] DMA: PL330: Add device tree support Thomas Abraham
2011-08-26  8:40         ` Thomas Abraham
2011-08-26  8:40         ` [PATCH 5/6] ARM: SAMSUNG: Add device tree support for pl330 dma engine wrappers Thomas Abraham
2011-08-26  8:40           ` Thomas Abraham
2011-08-26  8:40           ` [PATCH 6/6] ARM: EXYNOS4: Limit usage of pl330 device instance to non-dt build Thomas Abraham
2011-08-26  8:40             ` Thomas Abraham
2011-08-26 13:16         ` [PATCH 4/6] DMA: PL330: Add device tree support Rob Herring
2011-08-26 13:16           ` Rob Herring
2011-08-26 14:23           ` Russell King - ARM Linux [this message]
2011-08-26 14:23             ` Russell King - ARM Linux
2011-08-30 12:21             ` Thomas Abraham
2011-08-30 12:21               ` Thomas Abraham
     [not found]           ` <4E579C9B.7030807-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-08-30 12:18             ` Thomas Abraham
2011-08-30 13:19               ` Rob Herring
2011-08-30 13:19                 ` Rob Herring
2011-08-31  6:46                 ` Thomas Abraham
2011-08-31  6:46                   ` Thomas Abraham
2011-08-31 12:51                   ` Rob Herring
2011-08-31 12:51                     ` Rob Herring
2011-08-31 15:46                     ` Thomas Abraham
2011-08-31 15:46                       ` Thomas Abraham
2011-08-31 16:04                       ` Rob Herring
2011-08-31 16:04                         ` Rob Herring
2011-09-01  9:03                         ` Thomas Abraham
2011-09-01  9:03                           ` Thomas Abraham
2011-08-30 13:09           ` Thomas Abraham
2011-08-30 13:09             ` Thomas Abraham
2011-08-29 17:29 ` [PATCH 0/6] Add device tree support for PL330 dma controller driver Vinod Koul
2011-08-29 17:29   ` Vinod Koul
2011-08-30 12:28   ` Thomas Abraham
2011-08-30 12:28     ` Thomas Abraham
2011-09-05 13:14     ` Vinod Koul
2011-09-05 13:14       ` Vinod Koul
2011-09-05  5:17   ` Kukjin Kim
2011-09-05  5:17     ` Kukjin Kim
2011-09-05 10:16     ` Thomas Abraham
2011-09-05 10:16       ` Thomas Abraham
2011-09-19  6:28 [PATCH v4 " Thomas Abraham
2011-09-19  6:28 ` [PATCH 1/6] DMA: PL330: move filter function into driver Thomas Abraham
2011-09-19  6:28   ` [PATCH 2/6] DMA: PL330: Infer transfer direction from transfer request instead of platform data Thomas Abraham
2011-09-19  6:28     ` [PATCH 3/6] ARM: EXYNOS4: Modify platform data for pl330 driver Thomas Abraham
2011-09-19  6:29       ` [PATCH 4/6] DMA: PL330: Add device tree support Thomas Abraham
2011-09-19  6:29         ` Thomas Abraham

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