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

2 messages, 2 authors, 2016-02-09 · open the first message on its own page

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

From: Robert Jarzmik <robert.jarzmik@free.fr>
Date: 2016-02-09 07:20:13

Vinod Koul [off-list ref] writes:
On Mon, Feb 08, 2016 at 03:18:51PM +0100, Robert Jarzmik wrote:
quoted
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

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

From: Vinod Koul <hidden>
Date: 2016-02-09 15:16:27

On Tue, Feb 09, 2016 at 08:20:05AM +0100, Robert Jarzmik wrote:
Vinod Koul [off-list ref] writes:
quoted
On Mon, Feb 08, 2016 at 03:18:51PM +0100, Robert Jarzmik wrote:
quoted
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.
Somehow that does not sound right to me. You seem to have no way of knowing
what is the actual max request line for a platforms. What if on pxa25x user
requests more than 40 lines?
quoted
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.
The information that you have X lines on a platform needs to be described
and queried. I see current approach error prone

-- 
~Vinod
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