Re: [PATCH] dmaengine: rcar-dmac: Wait for IRQs completion when freeing channel

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Vinod,

On Monday 05 October 2015 15:11:55 Vinod Koul wrote:
> On Tue, Sep 15, 2015 at 12:11:33AM +0000, Kuninori Morimoto wrote:
> > Hi Laurent
> > 
> > > When freeing channel resources we need to ensure that no IRQ will occur
> > > for the given channel. In order to do so the driver stops the hardware,
> > > but an IRQ handler could still be running, especially given that the
> > > channel IRQ is threaded. Fix it by waiting for pending IRQs completion
> > > with synchronize_irq()
> > > 
> > > Signed-off-by: Laurent Pinchart
> > > <laurent.pinchart+renesas@ideasonboard.com>
> > > ---
> > > 
> > >  drivers/dma/sh/rcar-dmac.c | 37 +++++++++++++++++++------------------
> > >  1 file changed, 19 insertions(+), 18 deletions(-)
> > > 
> > > Hi Morimoto-san,
> > > 
> > > This patch is compile-tested only. Would you be able to check if it
> > > fixes the issue you've reported with SDHI and rcar-dmac ?
> > 
> > Thanks. I will ask to BSP team
> 
> Patch looks okay, but if we get this confirmation it would be great.

I've just received a report that the patch has been successfully tested to get 
rid of the oops, but it introduced another issue in that synchronize_irq() 
gets called from non-sleeptable context through terminate_all(). 

The DMA engine API states that

   * device_terminate_all
     - Aborts all the pending and ongoing transfers on the channel
     - This command should operate synchronously on the channel,
       terminating right away all the channels

I wonder how to interpret "synchronously" here, should terminate_all() wait 
for termination to be complete ? In that case it wouldn't be valid to call it 
from non-sleepable context.

-- 
Regards,

Laurent Pinchart