Re: [PATCH 2/4] dmaengine: ti: cppi41: Fix register access in suspend_late

["Adivi, Sai Sree Kartheek" <s-adivi@ti.com>]

On 04/11/26 01:07, Markus Schneider-Pargmann (TI) wrote:
> cppi41_suspend() and cppi41_resume() access registers. However the
> device may be runtime suspended in which case it is not allowed to
> access the registers.
>
> On suspend do not run disable_sched() when it is runtime suspended. This
> avoids accessing the registers and crashing the kernel during suspend.
>
> Resume when runtime suspended is delayed until cppi41_runtime_resume()
> is called using the variable ctx_lost. This keeps any access while the
> device is runtime suspended.
>
> Fixes: fdea2d09b997 ("dmaengine: cppi41: Add basic PM runtime support")
> Cc: stable@vger.kernel.org
> Signed-off-by: Markus Schneider-Pargmann (TI) <msp@baylibre.com>
Reviewed-by: Sai Sree Kartheek Adivi <s-adivi@ti.com>
> ---
>   drivers/dma/ti/cppi41.c | 16 +++++++++++++++-
>   1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/ti/cppi41.c b/drivers/dma/ti/cppi41.c
> index 458d20b12462..f5a824418fe7 100644
> --- a/drivers/dma/ti/cppi41.c
> +++ b/drivers/dma/ti/cppi41.c
> @@ -146,6 +146,9 @@ struct cppi41_dd {
>   	struct list_head pending;	/* Pending queued transfers */
>   	spinlock_t lock;		/* Lock for pending list */
>   
> +	/* Register context may have been lost during system suspend */
> +	bool ctx_lost;
> +
>   	bool is_suspended;
>   };
>   
> @@ -1171,7 +1174,10 @@ static int __maybe_unused cppi41_suspend(struct device *dev)
>   {
>   	struct cppi41_dd *cdd = dev_get_drvdata(dev);
>   
> -	disable_sched(cdd);
> +	if (!pm_runtime_status_suspended(dev))
> +		disable_sched(cdd);
> +
> +	cdd->ctx_lost = true;
>   
>   	return 0;
>   }
> @@ -1182,6 +1188,9 @@ static int __maybe_unused cppi41_resume(struct device *dev)
>   	struct cppi41_channel *c;
>   	int i;
>   
> +	if (pm_runtime_status_suspended(dev))
> +		return 0;
> +
>   	for (i = 0; i < DESCS_AREAS; i++)
>   		cppi_writel(cdd->descs_phys, cdd->qmgr_mem + QMGR_MEMBASE(i));
>   
> @@ -1196,6 +1205,8 @@ static int __maybe_unused cppi41_resume(struct device *dev)
>   	cppi_writel(QMGR_SCRATCH_SIZE, cdd->qmgr_mem + QMGR_LRAM_SIZE);
>   	cppi_writel(0, cdd->qmgr_mem + QMGR_LRAM1_BASE);
>   
> +	cdd->ctx_lost = false;
> +
>   	return 0;
>   }
>   
> @@ -1217,6 +1228,9 @@ static int __maybe_unused cppi41_runtime_resume(struct device *dev)
>   	struct cppi41_dd *cdd = dev_get_drvdata(dev);
>   	unsigned long flags;
>   
> +	if (cdd->ctx_lost)
> +		cppi41_resume(dev);
> +
>   	spin_lock_irqsave(&cdd->lock, flags);
>   	cdd->is_suspended = false;
>   	cppi41_run_queue(cdd);
>