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

On Tue, Jul 21, 2026 at 3:55 AM Andy Shevchenko
[off-list ref] wrote:

On Tue, Jul 21, 2026 at 12:21:13AM +0800, Shih-Yuan Lee wrote:

quoted

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.

Hi Andy,

Thanks for the feedback.

.runtime_suspend()

// this is how we refer to the callbacks.

Updated the commit message to format PM callbacks as .runtime_suspend().

...

quoted

+     /* 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.
 */

Updated the multi-line comment in pxa2xx_spi_remove() to adhere to the
standard Linux kernel multi-line comment style with an empty starting
line.

Thanks,
Shih-Yuan