> -----Original Message-----
> From: Vinod Koul <vkoul@xxxxxxxxxx>
> Sent: Tuesday, December 10, 2019 11:31 AM
> To: Radhey Shyam Pandey <radheys@xxxxxxxxxx>
> Cc: dan.j.williams@xxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>;
> nick.graumann@xxxxxxxxx; andrea.merello@xxxxxxxxx; Appana Durga
> Kedareswara Rao <appanad@xxxxxxxxxx>; mcgrof@xxxxxxxxxx;
> dmaengine@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; git
> <git@xxxxxxxxxx>
> Subject: Re: [PATCH] dmaengine: xilinx_dma: Reset DMA channel in
> dma_terminate_all
>
> On 25-11-19, 12:12, Radhey Shyam Pandey wrote:
> > Reset DMA channel after stop to ensure that pending transfers and
> > FIFOs in the datapath are flushed or completed. It fixes intermittent
> > data verification failure reported by xilinx dma test client.
> >
> > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> > ---
> > drivers/dma/xilinx/xilinx_dma.c | 17 +++++++++--------
> > 1 file changed, 9 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_dma.c
> > b/drivers/dma/xilinx/xilinx_dma.c index a9c5d5c..6f1539c 100644
> > --- a/drivers/dma/xilinx/xilinx_dma.c
> > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > @@ -2404,16 +2404,17 @@ static int xilinx_dma_terminate_all(struct
> dma_chan *dchan)
> > u32 reg;
> > int err;
> >
> > - if (chan->cyclic)
> > - xilinx_dma_chan_reset(chan);
>
> So reset is required for non cyclic cases as well now?
Yes. In absence of reset in non-cyclic case, when dmatest client
driver is stressed and loaded/unloaded multiple times we see dma
data comparison failures. Possibly IP is prefetching/holding the
previous state and reset ensures a clean state on each iteration.
>
> > -
> > - err = chan->stop_transfer(chan);
> > - if (err) {
> > - dev_err(chan->dev, "Cannot stop channel %p: %x\n",
> > - chan, dma_ctrl_read(chan,
> XILINX_DMA_REG_DMASR));
> > - chan->err = true;
> > + if (!chan->cyclic) {
> > + err = chan->stop_transfer(chan);
>
> no stop for cyclic now..?
After reset stop is not needed, so for the cyclic mode we only do reset.
>
> > + if (err) {
> > + dev_err(chan->dev, "Cannot stop channel %p: %x\n",
> > + chan, dma_ctrl_read(chan,
> > + XILINX_DMA_REG_DMASR));
> > + chan->err = true;
> > + }
> > }
> >
> > + xilinx_dma_chan_reset(chan);
> > /* Remove and free all of the descriptors in the lists */
> > xilinx_dma_free_descriptors(chan);
> > chan->idle = true;
> > --
> > 2.7.4
>
> --
> ~Vinod
