Re: [PATCH v5 1/3] spi: tegra210-quad: Convert to hard IRQ with high-priority workqueue

[Mark Brown]

On Wed, Jul 08, 2026 at 01:12:55AM +0000, Vishwaroop A wrote:

> Threaded IRQ handlers suffer from scheduler latency on heavily loaded
> systems, causing false transfer timeouts. Convert to a hard IRQ handler
> that schedules work on a high-priority unbound workqueue.

The high priority workqueue is a SCHED_NORMAL task with priority -20 so
it can be starved by real time tasks running at SCHED_FIFO, interrupt
threads are SCHED_FIFO (see the start of irq_thread()) so are harder to
starve.

> -	if (!t) {
> +static void tegra_qspi_work_handler(struct work_struct *work)
>  {

> -	 * If no transfer is in progress, check if this was a real interrupt
> -	 * that the timeout handler already processed, or a spurious one.
> +	 * tegra_qspi_handle_timeout() calls cancel_work_sync() before it
> +	 * invokes handle_{cpu,dma}_based_xfer() itself, so this work is

That's actually in patch 2 so we have a bisect issue here.  Not sure how
critical that is though.

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