Re: [PATCH v2 0/3] dmaengine: rcar-dmac: fix resource freeing synchronization

[Vinod Koul <vinod.koul@intel.com>]

On Tue, May 16, 2017 at 01:09:14AM +0200, Niklas S�derlund wrote:
> Hi,
> 
> This series fix resource freeing synchronization by:
> 
> 1. Patch 1/3
>    Store the IRQ number in the global struct so it can be used later
>    together with synchronize_irq().
> 
> 2. Patch 2/3
>    Adding support for the device_synchronize() callback in patch 2/3.
> 
> 3. Patch 3/3
>    Waiting for any ISR that might still be running after the channel is
>    halted prior to freeing its resources. This was patch previously part
>    of a patch sent out by Yoshihiro Shimoda and authored by Hiroyuki
>    Yokoyama, see [1].
> 
>    In that thread it was suggested by Lars-Peter Clausen to instead
>    implement the device_synchronize() callback. Unfortunately this is not
>    enough to solve the issue. In rcar_dmac_free_chan_resources() the
>    channel is halted by a call to rcar_dmac_chan_halt() and then directly
>    moves on to freeing resources, here it is still needed to add a wait
>    for any ISR to finish before freeing the resources, despite that a
>    device_synchronize() have been added.  This is because call chain:
> 
>    dma_release_channel()
>      dma_chan_put()
>        dmaengine_synchronize()
>        rcar_dmac_free_chan_resources()
>          rcar_dmac_chan_halt()
> 
>    Here dmaengine_synchronize() is called prior to rcar_dmac_chan_halt()
>    so an extra synchronisation to wait for any running ISR is still
>    needed.
> 
> By both adding a device_synchronize() which can be used in conjunction
> with device_terminate_all() and fiends and by adding an explicit
> synchronize_irq() when freeing channel resources I feel the
> synchronisation for freeing channel resources are in a much better
> shape. It also solves the issue in the original mail thread.

Applied now, thanks

-- 
~Vinod