Re: [PATCH v5 13/17] dmaengine: sh: rz-dmac: Add runtime PM support

[Frank Li]

On Tue, May 12, 2026 at 03:12:14PM +0300, Claudiu Beznea wrote:
> Protect the driver exposed APIs with runtime PM suspend/resume calls
> before accessing HW registers. As the current driver leaves runtime PM
> enabled in probe, the purpose of the changes in this patch is to avoid
> accessing HW registers after a failed system suspend leaves the runtime
> PM state of the device improperly reinitialized.
>
> In that case, the driver remains bound to the device, the APIs are still
> exposed, and any access to HW registers without runtime resuming the
> device may lead to synchronous aborts.
>
> This patch prepares the driver for suspend-to-RAM support.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
> ---
>
> Changes in v5:
> - none, this patch is new
>
>  drivers/dma/sh/rz-dmac.c | 48 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 48 insertions(+)
>
> diff --git a/drivers/dma/sh/rz-dmac.c b/drivers/dma/sh/rz-dmac.c
> index d6ad070be705..df91657fd5e3 100644
> --- a/drivers/dma/sh/rz-dmac.c
> +++ b/drivers/dma/sh/rz-dmac.c
> @@ -488,7 +488,15 @@ static void rz_dmac_prepare_descs_for_cyclic(struct rz_dmac_chan *channel)
>
>  static void rz_dmac_xfer_desc(struct rz_dmac_chan *chan)
>  {
> +	struct dma_chan *ch = &chan->vc.chan;
> +	struct rz_dmac *dmac = to_rz_dmac(ch->device);
>  	struct virt_dma_desc *vd;
> +	int ret;
> +
> +	PM_RUNTIME_ACQUIRE_IF_ENABLED(dmac->dev, pm);
> +	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
> +	if (ret)
> +		return;

According vnod comment *_prep() call may be called in atomic context
(complete callback). but runtime_pm may sleep.

Frank

>