Re: [PATCH v3 2/2] spi: qcom-geni: Add panic notifier to cancel and reset DMA during panic

[Jyothi Kumar Seerapu <jyothi.seerapu@oss.qualcomm.com>]

On 8/18/2026 6:58 PM, Praveen Talari wrote:
> When a VM crashes with an active SPI DMA transfer in progress, the
> SMMU raises context faults as the DMA engine continues to access
> IOVAs that are invalidated when the VM's memory context is torn down.
> These faults can affect other VMs sharing the same SMMU instance and
> obscure the root cause of the crash.
> 
> Register a panic notifier that cancels (or aborts, if cancel doesn't
> complete) the in-flight command and resets the TX/RX DMA FSMs, so the
> DMA engine stops issuing transactions against invalidated IOVAs
> before the system halts. For GPI DMA mode, the DMA channels are
> terminated directly via dmaengine_terminate_async().
> 
> The notifier bails out early if the device is not runtime-active or
> if there's no active GENI command, avoiding unnecessary register
> accesses while the SE is clock-gated or idle.
> 
> Since panic notifiers run with IRQs and preemption disabled,
> completion-based waits used by the regular error-handling path
> (handle_se_timeout()) cannot be reused here. Instead, the relevant
> status registers are polled directly with
> readl_poll_timeout_atomic(), which is safe to call in this context.
> 
> Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
> ---
>   drivers/spi/spi-geni-qcom.c | 68 +++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 68 insertions(+)
> 
> diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
> index c65c1788325d..f272bd0cb640 100644
> --- a/drivers/spi/spi-geni-qcom.c
> +++ b/drivers/spi/spi-geni-qcom.c
> @@ -12,8 +12,10 @@
>   #include <linux/dma/qcom-gpi-dma.h>
>   #include <linux/interrupt.h>
>   #include <linux/io.h>
> +#include <linux/iopoll.h>
>   #include <linux/log2.h>
>   #include <linux/module.h>
> +#include <linux/panic_notifier.h>
>   #include <linux/platform_device.h>
>   #include <linux/pm_opp.h>
>   #include <linux/pm_runtime.h>
> @@ -115,6 +117,7 @@ struct spi_geni_master {
>   	struct dma_chan *rx;
>   	int cur_xfer_mode;
>   	const struct geni_spi_desc *dev_data;
> +	struct notifier_block panic_nb;
>   };
>   
>   static void spi_slv_setup(struct spi_geni_master *mas)
> @@ -1073,6 +1076,62 @@ static void spi_geni_shutdown(struct platform_device *pdev)
>   	spi_controller_suspend(spi);
>   }
>   
> +static int spi_geni_panic_notifier(struct notifier_block *nb,
> +				   unsigned long action, void *data)
> +{
> +	struct spi_geni_master *mas = container_of(nb, struct spi_geni_master, panic_nb);
> +	struct spi_controller *spi = dev_get_drvdata(mas->dev);
> +	struct geni_se *se = &mas->se;
> +	u32 val;
> +
> +	if (!pm_runtime_active(mas->dev))
> +		return NOTIFY_OK;
> +
> +	if (mas->cur_xfer_mode == GENI_GPI_DMA) {
> +		dmaengine_terminate_async(mas->tx);
> +		dmaengine_terminate_async(mas->rx);
> +		return NOTIFY_OK;
> +	}
> +
> +	if (!(readl_relaxed(se->base + SE_GENI_STATUS) & M_GENI_CMD_ACTIVE))
> +		return NOTIFY_OK;
> +
> +	if (!spi->target) {
> +		geni_se_cancel_m_cmd(se);
> +		if (!readl_poll_timeout_atomic(se->base + SE_GENI_M_IRQ_STATUS, val,
> +					       val & M_CMD_CANCEL_EN, 10, 50000)) {
> +			writel_relaxed(M_CMD_CANCEL_EN, se->base + SE_GENI_M_IRQ_CLEAR);
> +			return NOTIFY_OK;
Looks like a successful cancel here returns NOTIFY_OK directly, skipping 
the FSM reset block below it entirely. Is that the correct expectation 
?> +		}
> +	}
> +
> +	geni_se_abort_m_cmd(se);
> +	if (!readl_poll_timeout_atomic(se->base + SE_GENI_M_IRQ_STATUS, val,
> +				       val & M_CMD_ABORT_EN, 10, 50000))
> +		writel_relaxed(M_CMD_ABORT_EN, se->base + SE_GENI_M_IRQ_CLEAR);
> +
> +	if (mas->cur_xfer_mode == GENI_SE_DMA) {
> +		writel_relaxed(1, se->base + SE_DMA_TX_FSM_RST);
> +		readl_poll_timeout_atomic(se->base + SE_DMA_TX_IRQ_STAT, val,
> +					  val & TX_RESET_DONE, 10, 50000);
> +		writel_relaxed(val, se->base + SE_DMA_TX_IRQ_CLR);
> +
> +		writel_relaxed(1, se->base + SE_DMA_RX_FSM_RST);
> +		readl_poll_timeout_atomic(se->base + SE_DMA_RX_IRQ_STAT, val,
> +					  val & RX_RESET_DONE, 10, 50000);
> +		writel_relaxed(val, se->base + SE_DMA_RX_IRQ_CLR);
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static void spi_geni_unregister_notifiers(void *data)
> +{
> +	struct spi_geni_master *mas = data;
> +
> +	atomic_notifier_chain_unregister(&panic_notifier_list, &mas->panic_nb);
> +}
> +
>   static int spi_geni_probe(struct platform_device *pdev)
>   {
>   	int ret, irq;
> @@ -1161,6 +1220,15 @@ static int spi_geni_probe(struct platform_device *pdev)
>   	if (ret)
>   		return ret;
>   
> +	mas->panic_nb.notifier_call = spi_geni_panic_notifier;
> +	ret = atomic_notifier_chain_register(&panic_notifier_list, &mas->panic_nb);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_add_action_or_reset(dev, spi_geni_unregister_notifiers, mas);
> +	if (ret)
> +		return ret;
> +
>   	return devm_spi_register_controller(dev, spi);
>   }
>   
>