From: vinod.koul@intel•com (Vinod Koul)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 4/5] dma: mmp_pdma: add support for residue reporting
Date: Fri, 13 Sep 2013 10:21:35 +0530 [thread overview]
Message-ID: <20130913045135.GI17188@intel.com> (raw)
In-Reply-To: <522F3ECB.3070307@gmail.com>
On Tue, Sep 10, 2013 at 05:46:19PM +0200, Daniel Mack wrote:
> Hi Vinod,
>
> Sorry for the late response, I've been on vacations.
>
> On 25.08.2013 18:33, Vinod Koul wrote:
> > On Wed, Aug 21, 2013 at 02:08:57PM +0200, Daniel Mack wrote:
> >> In order to report the channel's residue, we walk the list of running
> >> descriptors, look for those which match the cookie, and then try to find
> >> the descriptor which defines upper and lower boundaries that embrace the
> >> current transport pointer.
> >
> >>
> >> + /*
> >> + * 'passed' will be latched once we found the descriptor which
> >> + * lies inside the boundaries of the curr pointer. All
> >> + * descriptors that occur in the list _after_ we found that
> >> + * partially handled descriptor are still to be processed and
> >> + * are hence added to the residual bytes counter.
> >> + */
> > do you have multiple descriptors for one transaction? Should be No.
>
> Sure, that can be the case. One transaction could span across multiple
> descriptors, especially if its overall length exceeds the maximum length
> of one descriptor.
Yes and these addiional descriptor for a transacation should be child
descriptors.
The child descriptors should have ->parent point to parent descriptor and ->next
to next in the chain of children.
> > The cookie is assigned to a transaction when it is submitted. so when you see
> > descriptor cookie is less than completed one, then it already completed and
> > should not be in pending list.
>
> Hmm, what about an integer overrun?
The cookie needs to wrapped to 1. If you use virtual dma code then it would be
done. Since the variable is 32bit, i dont think you will have so many eonding
trasaction so i havent seen any concerns on that.
~Vinod
--
next prev parent reply other threads:[~2013-09-13 4:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-21 12:08 [PATCH v5 0/5] dma: pdma: cyclic, residue, DMA_PRIVATE Daniel Mack
2013-08-21 12:08 ` [PATCH v5 1/5] dma: mmp_pdma: only complete one transaction from dma_do_tasklet() Daniel Mack
2013-08-21 12:08 ` [PATCH v5 2/5] dma: mmp_pdma: don't clear DCMD_ENDIRQEN at end of pending chain Daniel Mack
2013-08-21 12:08 ` [PATCH v5 3/5] dma: mmp_pdma: add support for cyclic DMA descriptors Daniel Mack
2013-08-21 12:08 ` [PATCH v5 4/5] dma: mmp_pdma: add support for residue reporting Daniel Mack
2013-08-25 16:33 ` Vinod Koul
2013-09-10 15:46 ` Daniel Mack
2013-09-13 4:51 ` Vinod Koul [this message]
2013-12-09 19:00 ` Daniel Mack
2013-12-10 16:11 ` Vinod Koul
2013-12-11 15:09 ` Daniel Mack
2013-08-25 18:08 ` Russell King - ARM Linux
2013-09-10 15:46 ` Daniel Mack
2013-08-21 12:08 ` [PATCH v5 5/5] dma: mmp_pdma: set DMA_PRIVATE Daniel Mack
2013-08-25 16:35 ` [PATCH v5 0/5] dma: pdma: cyclic, residue, DMA_PRIVATE Vinod Koul
2013-08-26 9:22 ` Daniel Mack
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