linux-kernel - Re: [PATCH 1/8] dmaengine: ste_dma40: Assign memcpy channels in the driver

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Date:	Wed, 24 Apr 2013 17:05:29 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus WALLEIJ <linus.walleij@...ricsson.com>,
	Arnd Bergmann <arnd@...db.de>,
	Vinod Koul <vinod.koul@...el.com>,
	Per Forlin <per.forlin@...ricsson.com>,
	Dan Williams <djbw@...com>
Subject: Re: [PATCH 1/8] dmaengine: ste_dma40: Assign memcpy channels in the driver

On Wed, Apr 24, 2013 at 4:54 PM, Lee Jones <lee.jones@...aro.org> wrote:
> On 24 April 2013 14:45, Linus Walleij <linus.walleij@...aro.org> wrote:
>> On Tue, Apr 9, 2013 at 8:39 PM, Lee Jones <lee.jones@...aro.org> wrote:
>>
>> > The channels reserved for memcpy are the same for all currently
>> > supported platforms. With this in mind, we can ease the platform
>> > data passing requirement by moving these assignments out from
>> > platform code and place them directly into the driver.
>> >
>> > Cc: Vinod Koul <vinod.koul@...el.com>
>> > Cc: Dan Williams <djbw@...com>
>> > Cc: Per Forlin <per.forlin@...ricsson.com>
>> > Acked-by: Arnd Bergmann <arnd@...db.de>
>> > Signed-off-by: Lee Jones <lee.jones@...aro.org>
>>
>> (...)
>>
>> > -/* Reserved event lines for memcpy only */
>> > -static int dma40_memcpy_event[] = {
>> > -       DB8500_DMA_MEMCPY_TX_0,
>> > -       DB8500_DMA_MEMCPY_TX_1,
>> > -       DB8500_DMA_MEMCPY_TX_2,
>> > -       DB8500_DMA_MEMCPY_TX_3,
>> > -       DB8500_DMA_MEMCPY_TX_4,
>> > -       DB8500_DMA_MEMCPY_TX_5,
>> > -};
>>
>> (...)
>>
>> > +/* Reserved event lines for memcpy only. */
>> > +static int dma40_memcpy_channels[] = { 56, 57, 58, 59, 60 };
>>
>> So what's so bad with using the #defines?
>>
>> I would prefer if you took the entire content of
>> arch/arm/mach-ux500/ste-dma40-db8500.h
>> and copied into the DMA driver, so you atleast
>> have a chance of understanding what these numbers
>> are about.
>
>
> I did attempt to do that, but Arnd NAK:ed it:
>
> "Hmm, not sure about this one. The slave numbers are not really
> platform_data and I think they should not be exposed to drivers. It
> makes sense to keep the numbers for the memcpy channels in the driver
> itself as they are hardwired in the driver, but the slave channels
> should stay in the platform I think."
>
> ... and I didn't want to duplicate the defines, but I'll so whatever
> you choose.

I don't think I agree.

OK atleast define the numbers with something like
#define DB8500_DMA_MEMCPY_TX_0 56
etc, just hard-coding the numbers is pretty unhelpful, OK?

Ultimately these 5 numbers should (optionally) come in from
the device tree node for the DMA40 itself, maybe a later patch
adds that...?

Yours,
Linus Walleij
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