RE: [PATCH v3 2/2] dmaengine: vdma: Fix race condition in Non-SG mode

[Appana Durga Kedareswara Rao]

Hi Vinod,

> -----Original Message-----
> From: Vinod Koul [mailto:vinod.koul@xxxxxxxxx]
> Sent: Wednesday, April 06, 2016 3:23 AM
> To: Appana Durga Kedareswara Rao <appanad@xxxxxxxxxx>
> Cc: dan.j.williams@xxxxxxxxx; Michal Simek <michals@xxxxxxxxxx>; Soren
> Brinkmann <sorenb@xxxxxxxxxx>; Appana Durga Kedareswara Rao
> <appanad@xxxxxxxxxx>; moritz.fischer@xxxxxxxxx;
> laurent.pinchart@xxxxxxxxxxxxxxxx; luis@xxxxxxxxxxxxxxxxx; Srikanth
> Vemula <svemula@xxxxxxxxxx>; Anirudha Sarangi <anirudh@xxxxxxxxxx>;
> dmaengine@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v3 2/2] dmaengine: vdma: Fix race condition in Non-SG
> mode
> 
> On Fri, Mar 25, 2016 at 02:46:39PM +0530, Kedareswara rao Appana wrote:
> > When VDMA is configured in  Non-sg mode Users can queue descriptors
> > greater than h/w configured frames.
> >
> > Current driver allows the user to queue descriptors upto h/w configured.
> > Which is wrong for non-sg mode configuration.
> 
> I see to have standalone patch 2, where is 1st patch?
> 
> There seems to be an issue with other 6 patch series with threading broken and
> few patches showing up standalone and not part of series
> 
> Can you resend the whole thing please..

Ok Sure will resend both the patch series again....

Regards,
Kedar.

> 
> >
> > This patch fixes this issue.
> >
> > Signed-off-by: Kedareswara rao Appana <appanad@xxxxxxxxxx>
> > ---
> > Changes for v3:
> > ---> New patch.
> >
> >  drivers/dma/xilinx/xilinx_vdma.c | 25 +++++++++++++++++++------
> >  1 file changed, 19 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_vdma.c
> > b/drivers/dma/xilinx/xilinx_vdma.c
> > index abe915c..b873d98 100644
> > --- a/drivers/dma/xilinx/xilinx_vdma.c
> > +++ b/drivers/dma/xilinx/xilinx_vdma.c
> > @@ -209,6 +209,7 @@ struct xilinx_vdma_tx_descriptor {
> >   * @flush_on_fsync: Flush on Frame sync
> >   * @desc_pendingcount: Descriptor pending count
> >   * @ext_addr: Indicates 64 bit addressing is supported by dma channel
> > + * @desc_submitcount: Descriptor h/w submitted count
> >   */
> >  struct xilinx_vdma_chan {
> >  	struct xilinx_vdma_device *xdev;
> > @@ -233,6 +234,7 @@ struct xilinx_vdma_chan {
> >  	bool flush_on_fsync;
> >  	u32 desc_pendingcount;
> >  	bool ext_addr;
> > +	u32 desc_submitcount;
> >  };
> >
> >  /**
> > @@ -716,9 +718,10 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_vdma_chan *chan)
> >  		struct xilinx_vdma_tx_segment *segment, *last = NULL;
> >  		int i = 0;
> >
> > -		list_for_each_entry(desc, &chan->pending_list, node) {
> > -			segment = list_first_entry(&desc->segments,
> > -					   struct xilinx_vdma_tx_segment,
> node);
> > +		if (chan->desc_submitcount < chan->num_frms)
> > +			i = chan->desc_submitcount;
> > +
> > +		list_for_each_entry(segment, &desc->segments, node) {
> >  			if (chan->ext_addr)
> >  				vdma_desc_write_64(chan,
> >
> 	XILINX_VDMA_REG_START_ADDRESS_64(i++),
> > @@ -742,8 +745,17 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_vdma_chan *chan)
> >  		vdma_desc_write(chan, XILINX_VDMA_REG_VSIZE, last-
> >hw.vsize);
> >  	}
> >
> > -	list_splice_tail_init(&chan->pending_list, &chan->active_list);
> > -	chan->desc_pendingcount = 0;
> > +	if (!chan->has_sg) {
> > +		list_del(&desc->node);
> > +		list_add_tail(&desc->node, &chan->active_list);
> > +		chan->desc_submitcount++;
> > +		chan->desc_pendingcount--;
> > +		if (chan->desc_submitcount == chan->num_frms)
> > +			chan->desc_submitcount = 0;
> > +	} else {
> > +		list_splice_tail_init(&chan->pending_list, &chan->active_list);
> > +		chan->desc_pendingcount = 0;
> > +	}
> >  }
> >
> >  /**
> > @@ -927,7 +939,8 @@ append:
> >  	list_add_tail(&desc->node, &chan->pending_list);
> >  	chan->desc_pendingcount++;
> >
> > -	if (unlikely(chan->desc_pendingcount > chan->num_frms)) {
> > +	if (chan->has_sg &&
> > +	    unlikely(chan->desc_pendingcount > chan->num_frms)) {
> >  		dev_dbg(chan->dev, "desc pendingcount is too high\n");
> >  		chan->desc_pendingcount = chan->num_frms;
> >  	}
> > --
> > 2.1.2
> >
> > --
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> 
> --
> ~Vinod