[PATCH] dmaengine: ti: omap-dma: Block PM if SDMA is busy to fix audio

[Peter Ujfalusi]

Hi Tony,

On 09/11/2020 17.40, Tony Lindgren wrote:
> We now use cpu_pm for saving and restoring device context for deeper SoC
> idle states. But for omap3, we must also block idle if SDMA is busy.
> 
> If we don't block idle when SDMA is busy, we eventually end up saving and
> restoring SDMA register state on PER domain idle while SDMA is active and
> that causes at least audio playback to fail.

Thanks for the fix!

Tested-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi at ti.com>

Vinod: Can you take this for 5.10 as a fix? The off mode got enabled by
default in 5.10-rc1 and audio got broken out of box.

Thanks,
- Péter

> Fixes: 4c74ecf79227 ("dmaengine: ti: omap-dma: Add device tree match data and use it for cpu_pm")
> Reported-by: Peter Ujfalusi <peter.ujfalusi at ti.com>
> Signed-off-by: Tony Lindgren <tony at atomide.com>
> ---
>  drivers/dma/ti/omap-dma.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
> --- a/drivers/dma/ti/omap-dma.c
> +++ b/drivers/dma/ti/omap-dma.c
> @@ -1522,29 +1522,38 @@ static void omap_dma_free(struct omap_dmadev *od)
>  	}
>  }
>  
> +/* Currently used by omap2 & 3 to block deeper SoC idle states */
> +static bool omap_dma_busy(struct omap_dmadev *od)
> +{
> +	struct omap_chan *c;
> +	int lch = -1;
> +
> +	while (1) {
> +		lch = find_next_bit(od->lch_bitmap, od->lch_count, lch + 1);
> +		if (lch >= od->lch_count)
> +			break;
> +		c = od->lch_map[lch];
> +		if (!c)
> +			continue;
> +		if (omap_dma_chan_read(c, CCR) & CCR_ENABLE)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +
>  /* Currently only used for omap2. For omap1, also a check for lcd_dma is needed */
>  static int omap_dma_busy_notifier(struct notifier_block *nb,
>  				  unsigned long cmd, void *v)
>  {
>  	struct omap_dmadev *od;
> -	struct omap_chan *c;
> -	int lch = -1;
>  
>  	od = container_of(nb, struct omap_dmadev, nb);
>  
>  	switch (cmd) {
>  	case CPU_CLUSTER_PM_ENTER:
> -		while (1) {
> -			lch = find_next_bit(od->lch_bitmap, od->lch_count,
> -					    lch + 1);
> -			if (lch >= od->lch_count)
> -				break;
> -			c = od->lch_map[lch];
> -			if (!c)
> -				continue;
> -			if (omap_dma_chan_read(c, CCR) & CCR_ENABLE)
> -				return NOTIFY_BAD;
> -		}
> +		if (omap_dma_busy(od))
> +			return NOTIFY_BAD;
>  		break;
>  	case CPU_CLUSTER_PM_ENTER_FAILED:
>  	case CPU_CLUSTER_PM_EXIT:
> @@ -1595,6 +1604,8 @@ static int omap_dma_context_notifier(struct notifier_block *nb,
>  
>  	switch (cmd) {
>  	case CPU_CLUSTER_PM_ENTER:
> +		if (omap_dma_busy(od))
> +			return NOTIFY_BAD;
>  		omap_dma_context_save(od);
>  		break;
>  	case CPU_CLUSTER_PM_ENTER_FAILED:
> 
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