[alsa-devel] [PATCH 2/2] ALSA: hda: fix to wait for RIRB & CORB DMA to set

[Takashi Iwai]

On Thu, 28 Apr 2016 15:06:05 +0200,
Vinod Koul wrote:
> 
> From: Jeeja KP <jeeja.kp at intel.com>
> 
> After setting the stop bit of RIRB/CORB DMA, we should wait for
> stop bit to be set.

What does this actually fix?

 
> Signed-off-by: Jeeja KP <jeeja.kp at intel.com>
> Signed-off-by: Vinod Koul <vinod.koul at intel.com>
> ---
>  sound/hda/hdac_controller.c | 33 +++++++++++++++++++++++++++++++--
>  1 file changed, 31 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
> index 8c486235c905..cc020c1706e7 100644
> --- a/sound/hda/hdac_controller.c
> +++ b/sound/hda/hdac_controller.c
> @@ -80,6 +80,35 @@ void snd_hdac_bus_init_cmd_io(struct hdac_bus *bus)
>  }
>  EXPORT_SYMBOL_GPL(snd_hdac_bus_init_cmd_io);
>  
> +
> +/* Stop CORB DMA and poll till they are stopped */
> +static void hdac_stop_corb_dma(struct hdac_bus *bus)
> +{
> +	unsigned long timeout;
> +
> +	snd_hdac_chip_writew(bus, CORBCTL, 0);
> +
> +	udelay(3);
> +	timeout = jiffies + msecs_to_jiffies(100);
> +	while ((snd_hdac_chip_readb(bus, CORBCTL) & AZX_CORBCTL_RUN)
> +		&& time_before(jiffies, timeout))
> +		udelay(10);
> +}
> +
> +/* Stop RIRB DMA and poll till they are stopped */
> +static void hdac_stop_rirb_dma(struct hdac_bus *bus)
> +{
> +	unsigned long timeout;
> +
> +	snd_hdac_chip_writew(bus, RIRBCTL, 0);
> +
> +	udelay(3);
> +	timeout = jiffies + msecs_to_jiffies(100);
> +	while ((snd_hdac_chip_readb(bus, RIRBCTL) & AZX_RBCTL_DMA_EN)
> +		&& time_before(jiffies, timeout))
> +		udelay(10);
> +}
> +
>  /**
>   * snd_hdac_bus_stop_cmd_io - clean up CORB/RIRB buffers
>   * @bus: HD-audio core bus
> @@ -88,8 +117,8 @@ void snd_hdac_bus_stop_cmd_io(struct hdac_bus *bus)
>  {
>  	spin_lock_irq(&bus->reg_lock);
>  	/* disable ringbuffer DMAs */
> -	snd_hdac_chip_writeb(bus, RIRBCTL, 0);
> -	snd_hdac_chip_writeb(bus, CORBCTL, 0);
> +	hdac_stop_rirb_dma(bus);
> +	hdac_stop_corb_dma(bus);

Doing these one after another sequentially is a waste of time.
Clear two once, then sync them.


thanks,

Takashi