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

Vinod Koul [off-list ref] writes:

On Tue, Feb 09, 2016 at 08:20:05AM +0100, Robert Jarzmik wrote:

quoted

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

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

Actually I have thought over your point, and you're quite right (this is your
case of more than 40 lines).

The exception I have found is :
 - a device driver is wrongly written
 - it requests the requestor line 0x1000 (below 0x8000)
 - pxa_dma computes the register in pxad_drcmr(0x1000)
   => this gives : base + 0x1000 + 4 * 0x1000 = base + 0x5000
   => this is a not existing iomapped register

So yes, I will respin the patchset, with :
 - one patch adding the number of requestors in mmp_dma.h
 - one patch adding the number of requestors in devicetree description
 - one patch adding the number of requestors in arch/arm/mach-pxa (my tree)
 - one patch adding the use of number of requestors in pxa_dma.c

Cheers.

-- 
Robert