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

[Claudiu Beznea <claudiu.beznea@kernel.org>]

Hi, Frank,

On 5/13/26 01:03, Frank Li wrote:
> 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@bp.renesas.com>
>> ---
>>
>> 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.

That's why the pm_runtime_irq_safe() was called in probe, to allow it being 
called in atomic context.

The series was tested with CONFIG_LOCKDEP=y and CONFIG_DEBUG_ATOMIC_SLEEP=y no 
issue was identified.

-- 
Thank you,
Claudiu