From mboxrd@z Thu Jan  1 00:00:00 1970
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Date: Tue, 18 Aug 2015 06:35:09 +0000
Subject: Re: Issues with rcar-dmac and sh-sci
Message-Id: <1696172.AK9gpuDPdv@avalon>
List-Id: <linux-sh.vger.kernel.org>
References: <alpine.DEB.2.10.1507162026200.821@ayla.of.borg>
In-Reply-To: <alpine.DEB.2.10.1507162026200.821@ayla.of.borg>
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To: linux-sh@vger.kernel.org

Hi Geert,

On Monday 17 August 2015 16:03:52 Geert Uytterhoeven wrote:
> On Sat, Aug 15, 2015 at 1:42 AM, Laurent Pinchart wrote:
> > From 131968befd5de3400631b879b1574beea27b8239 Mon Sep 17 00:00:00 2001
> > From: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > Date: Sat, 15 Aug 2015 01:28:28 +0300
> > Subject: [PATCH] dmaengine: rcar-dmac: Fix residue reporting for pending
> > 
> >  descriptors
> > 
> > Cookies corresponding to pending transfers have a residue value equal to
> > the full size of the corresponding descriptor. The driver miscomputes
> > that and uses the size of the active descriptor instead. Fix it.
> 
> Thanks!
> 
> > Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> > 
> >  drivers/dma/sh/rcar-dmac.c | 28 ++++++++++++++++++++++++++--
> >  1 file changed, 26 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> > index 7820d07e7bee..a98596a1f12f 100644
> > --- a/drivers/dma/sh/rcar-dmac.c
> > +++ b/drivers/dma/sh/rcar-dmac.c
> > @@ -1143,19 +1143,43 @@ static unsigned int
> > rcar_dmac_chan_get_residue(struct rcar_dmac_chan *chan,
> >         struct rcar_dmac_desc *desc = chan->desc.running;
> >         struct rcar_dmac_xfer_chunk *running = NULL;
> >         struct rcar_dmac_xfer_chunk *chunk;
> > +       enum dma_status status;
> >         unsigned int residue = 0;
> >         unsigned int dptr = 0;
> >         
> >         if (!desc)
> >                 return 0;
> > +
> > +       /*
> > +        * If the cookie corresponds to a descriptor that has been
> > completed
> > +        * there is no residue. The same check has already been performed
> > by the
> > +        * caller but without holding the channel lock, so the descriptor
> > could
> > +        * now be complete.
> > +        */
> > +       status = dma_cookie_status(&chan->chan, cookie, NULL);
> > +       if (status = DMA_COMPLETE)
> > +               return 0;
> > +
> >         /*
> >          * If the cookie doesn't correspond to the currently running
> >          transfer
> >          * then the descriptor hasn't been processed yet, and the residue
> >          is
> >          * equal to the full descriptor size.
> >          */
> > -       if (cookie != desc->async_tx.cookie)
> > -               return desc->size;
> > +       if (cookie != desc->async_tx.cookie) {
> > +               list_for_each_entry(desc, &chan->desc.pending, node) {
> > +                       if (cookie = desc->async_tx.cookie)
> > +                               return desc->size;
> > +               }
> 
> The descriptor may be either on the pending or active list, so I had to add
> 
> +               list_for_each_entry(desc, &chan->desc.active, node) {
> +                       if (cookie = desc->async_tx.cookie)
> +                               return desc->size;
> +               }
> 
> After that it seems to work fine. Will do more testing...

My bad. I'll fix that and submit the patch. Thank you for testing it.

> > +
> > +               /*
> > +                * No descriptor found for the cookie, there's thus no
> > residue.
> > +                * This shouldn't happen if the calling driver passes a
> > correct
> > +                * cookie value.
> > +                */
> > +               WARN(1, "No descriptor for cookie!");
> > +               return 0;
> > +       }

-- 
Regards,

Laurent Pinchart