[CFT 01/11] dmaengine: add OMAP DMA engine driver

[Russell King - ARM Linux]

On Fri, Jun 08, 2012 at 03:30:23PM +0530, Shilimkar, Santosh wrote:
> On Fri, Jun 8, 2012 at 2:32 PM, Russell King - ARM Linux
> <linux at arm.linux.org.uk> wrote:
> > On Thu, Jun 07, 2012 at 12:06:32PM +0100, Russell King wrote:
> >> Tested-by: Tony Lindgren <tony at atomide.com>
> >> Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> >> ---
> >>  drivers/dma/Kconfig      |    6 +
> >>  drivers/dma/Makefile     |    1 +
> >>  drivers/dma/omap-dma.c   |  522 ++++++++++++++++++++++++++++++++++++++++++++++
> >>  include/linux/omap-dma.h |   24 ++
> >>  4 files changed, 553 insertions(+), 0 deletions(-)
> >>  create mode 100644 drivers/dma/omap-dma.c
> >>  create mode 100644 include/linux/omap-dma.h
> >
> > There is a bug in here which no one has spotted... I just noticed it.
> >
> > diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
> > index 500bc71..02eb2fd 100644
> > --- a/drivers/dma/omap-dma.c
> > +++ b/drivers/dma/omap-dma.c
> > @@ -130,14 +130,13 @@ static void omap_dma_callback(int ch, u16 status, void *data)
> >
> >        spin_lock_irqsave(&c->vc.lock, flags);
> >        d = c->desc;
> > -       if (!d)
> > -               return;
> > -
> > -       if (++c->sgidx < d->sglen) {
> > -               omap_dma_start_sg(c, d, c->sgidx);
> > -       } else {
> > -               omap_dma_start_desc(c);
> > -               vchan_cookie_complete(&d->vd);
> > +       if (d) {
> > +               if (++c->sgidx < d->sglen) {
> > +                       omap_dma_start_sg(c, d, c->sgidx);
> > +               } else {
> > +                       omap_dma_start_desc(c);
> > +                       vchan_cookie_complete(&d->vd);
> > +               }
> >        }
> >        spin_unlock_irqrestore(&c->vc.lock, flags);
> >  }
> >
> You mean the lock release, right ?

Yes, if c->desc is NULL, we exit this function with the lock held,
which will lead to a lockup.