Re: [PATCH 1/3] spi: tegra210-quad: Convert to hard IRQ with high-priority workqueue

[Jon Hunter]

On 18/05/2026 17:07, Vishwaroop A wrote:
> Threaded IRQ handlers suffer from scheduler latency on heavily loaded
> systems, causing false transfer timeouts. Convert to hard IRQ handler
> that schedules work on a high-priority unbound workqueue.
>
> The hard IRQ handler verifies the interrupt, caches FIFO status,
> clears and masks interrupts, then schedules bottom-half processing.
> The workqueue handler runs in process context (can sleep for DMA)
> and can execute on any CPU, avoiding CPU0 bottlenecks.
>
> Signed-off-by: Vishwaroop A <va@xxxxxxxxxx>
> ---
>   drivers/spi/spi-tegra210-quad.c | 120 ++++++++++++++++++++++----------
>   1 file changed, 83 insertions(+), 37 deletions(-)

...

>   static struct tegra_qspi_soc_data tegra210_qspi_soc_data = {
> @@ -1793,12 +1826,21 @@ static int tegra_qspi_probe(struct platform_device *pdev)
>   
>   	pm_runtime_put_autosuspend(&pdev->dev);
>   
> -	ret = request_threaded_irq(tqspi->irq, NULL,
> -				   tegra_qspi_isr_thread, IRQF_ONESHOT,
> -				   dev_name(&pdev->dev), tqspi);
> +	tqspi->wq = alloc_workqueue("%s", WQ_HIGHPRI | WQ_UNBOUND, 0,
> +				    dev_name(&pdev->dev));

Why not used devm_alloc_workqueue() here?

> +	if (!tqspi->wq) {
> +		dev_err(&pdev->dev, "failed to allocate workqueue\n");
> +		ret = -ENOMEM;
> +		goto exit_pm_disable;
> +	}
> +
> +	INIT_WORK(&tqspi->irq_work, tegra_qspi_work_handler);
> +
> +	ret = request_irq(tqspi->irq, tegra_qspi_isr, IRQF_SHARED,
> +			  dev_name(&pdev->dev), tqspi);

And use devm_request_irq() here?

>   	if (ret < 0) {
>   		dev_err(&pdev->dev, "failed to request IRQ#%u: %d\n", tqspi->irq, ret);
> -		goto exit_pm_disable;
> +		goto exit_destroy_wq;
>   	}
>   
>   	ret = spi_register_controller(host);
> @@ -1810,7 +1852,9 @@ static int tegra_qspi_probe(struct platform_device *pdev)
>   	return 0;
>   
>   exit_free_irq:
> -	free_irq(qspi_irq, tqspi);
> +	free_irq(tqspi->irq, tqspi);
> +exit_destroy_wq:
> +	destroy_workqueue(tqspi->wq);
>   exit_pm_disable:
>   	pm_runtime_dont_use_autosuspend(&pdev->dev);
>   	pm_runtime_force_suspend(&pdev->dev);
> @@ -1825,6 +1869,8 @@ static void tegra_qspi_remove(struct platform_device *pdev)
>   
>   	spi_unregister_controller(host);
>   	free_irq(tqspi->irq, tqspi);
> +	flush_workqueue(tqspi->wq);
> +	destroy_workqueue(tqspi->wq);
>   	pm_runtime_dont_use_autosuspend(&pdev->dev);
>   	pm_runtime_force_suspend(&pdev->dev);
>   	tegra_qspi_deinit_dma(tqspi);

Jon

--
nvpublic