[PATCH v16 4/7] spi: pxa2xx: lock out runtime autosuspend for Intel LPSS SPI in PIO mode

[Andy Shevchenko]

On Tue, Jul 21, 2026 at 12:21:13AM +0800, Shih-Yuan Lee wrote:
> When operating in PIO mode on Intel LPSS SPI controllers, runtime PM
> autosuspend clock-gates the hardware block when idle. On subsequent
> transfers, MMIO accesses to trigger resume are performed before the runtime
> PM state machine can wake the controller, causing PCIe Completion Timeouts.
> This issue does not affect DMA mode, where the DMA engine holds the required
> resources, nor does it affect non-LPSS controllers.
> 
> Lock out runtime PM autosuspend for LPSS SPI controllers specifically
> when operating in PIO mode.
> 
> Acquire a runtime PM reference via pm_runtime_get_noresume() in
> pxa2xx_spi_probe() after registration, and release it via
> pm_runtime_put_noidle() in pxa2xx_spi_remove() before hardware teardown to
> ensure the runtime PM reference held in probe is released without invoking
> runtime_suspend on already-unclocked hardware.

.runtime_suspend()

// this is how we refer to the callbacks.


...

> +	/* Release the PM reference held in probe for LPSS PIO mode before
> +	 * hardware teardown so the PM core does not invoke runtime_suspend
> +	 * on already-unclocked hardware.
> +	 */

/*
 * Keep the comment style as per SPI and many other subsystems
 * and as in this example.
 */

-- 
With Best Regards,
Andy Shevchenko