linux-kernel - Re: [PATCH] dmaengine: pxa_dma: fix the maximum requestor line

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Message-ID: <878u2u2vve.fsf@belgarion.home>
Date:	Tue, 09 Feb 2016 08:20:05 +0100
From:	Robert Jarzmik <robert.jarzmik@...e.fr>
To:	Vinod Koul <vinod.koul@...el.com>
Cc:	Daniel Mack <daniel@...que.org>,
	Haojian Zhuang <haojian.zhuang@...il.com>,
	linux-arm-kernel@...ts.infradead.org, dmaengine@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: pxa_dma: fix the maximum requestor line

Vinod Koul <vinod.koul@...el.com> writes:

> On Mon, Feb 08, 2016 at 03:18:51PM +0100, Robert Jarzmik wrote:
>> The current number of requestor lines is limited to 31. This was an
>> error of a previous commit, as this number is platform dependent, and is
>> actually :
>>  - for pxa25x: 40 requestor lines
>>  - for pxa27x: 74 requestor lines
>>  - for pxa3xx: 100 requestor lines
>> 
>> As the driver doesn't need to know the exact number, but only an
>
> and why would that be a good assumption?
Well, the driver doesn't use the exact value. Would that be 128, 1000 or 10000,
it wouldn't change its behavior. The clients either pass -1UL (ie. no flow
control) or a requestor line number.

> Btw shouldn't this data come from DT?
It can if you wish, but in this case I must amend the platform data case too, ie
mmp_dma_platdata. And this has an impact on MMP architecture. I'd rather have
the simpler approach unless you really want the exact number of requestor lines
to be passed in platform_data+DT.

Cheers.

-- 
Robert