From mboxrd@z Thu Jan  1 00:00:00 1970
From: vinod.koul@intel.com (Vinod Koul)
Date: Tue, 9 Feb 2016 20:50:07 +0530
Subject: [PATCH] dmaengine: pxa_dma: fix the maximum requestor line
In-Reply-To: <878u2u2vve.fsf@belgarion.home>
References: <1454941131-12308-1-git-send-email-robert.jarzmik@free.fr>
 <20160209033646.GK19598@localhost> <878u2u2vve.fsf@belgarion.home>
Message-ID: <20160209152007.GQ19598@localhost>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Tue, Feb 09, 2016 at 08:20:05AM +0100, Robert Jarzmik wrote:
> Vinod Koul <vinod.koul@intel.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.

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?

> > 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