On 7/8/25 3:38 PM, Rafael J. Wysocki wrote: > On Tue, Jul 8, 2025 at 4:28 PM Tudor Ambarus <tudor.ambarus@xxxxxxxxxx> wrote: >> >> On some platforms, device dependencies are not properly represented by >> device links, which can cause issues when asynchronous power management >> is enabled. While it is possible to disable this via sysfs, doing so >> at runtime can race with the first system suspend event. >> >> This patch introduces a kernel command-line parameter, "pm_async", which >> can be set to "off" to globally disable asynchronous suspend and resume >> operations from early boot. This provides a robust way to fall back to >> synchronous (sequential) operation, which can stabilize platforms with >> problematic dependencies and also serve as a useful debugging tool. >> >> The default behavior remains unchanged (asynchronous enabled). To disable >> it, boot the kernel with the "pm_async=off" parameter. > > IIUC, this effectively is a way to change the initial value of the > existing pm_async sysfs knob. > > Might be worth mentioning in the changelog. > Right. Will update shortly. >> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx> >> --- >> Dealing with the pixel6 downstream drivers to cope with the changes from >> https://lore.kernel.org/linux-pm/10629535.nUPlyArG6x@xxxxxxxxxxxxx/. >> >> Similar to what people already reported it seems pixel6 lacks proper >> device links dependencies downstream causing i2c and spi client drivers >> to fail to suspend. Add kernel param to disable async suspend/resume. >> --- >> Documentation/admin-guide/kernel-parameters.txt | 9 +++++++++ >> kernel/power/main.c | 9 +++++++++ >> 2 files changed, 18 insertions(+) >> >> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt >> index f1f2c0874da9ddfc95058c464fdf5dabaf0de713..55ba3e747d86c09a0696e105a1d9cd99218f0c07 100644 >> --- a/Documentation/admin-guide/kernel-parameters.txt >> +++ b/Documentation/admin-guide/kernel-parameters.txt >> @@ -5000,6 +5000,15 @@ >> that number, otherwise (e.g., 'pmu_override=on'), MMCR1 >> remains 0. >> >> + pm_async [PM] >> + If set to "off", disables asynchronous suspend and >> + resume of devices during system-wide power transitions. >> + This can be useful on platforms where device >> + dependencies are not well-defined, or for debugging >> + power management issues. Defaults to "on" (asynchronous >> + operations enabled). > > And here too because it is now unclear how this relates to the pm_sync > under /sys/power/. Sounds good.
