[PATCH v2 0/3] soundwire: intel: exit clock-stop mode before system suspend

From: Bard Liao
Date: Tue Aug 17 2021 - 22:50:17 EST

Intel validation reported an issue where the HW_RST self-clearing bit
is not cleared in hardware, which as a ripple effect creates issues
with the clock stop mode.

This happens is a specific sequence where the Intel manager is
pm_runtime suspended with the clock-stop mode enabled. During the
system suspend, we currently do nothing, which can lead to potential
issues on system resume and the following pm_runtime suspend,
depending on the hardware state.

This patch suggests a full resume if the clock-stop mode is used. This
may require extra time but will make the suspend/resume flows
completely symmetric. This also removes a race condition where we
could not access SHIM registers if the parent was suspended as
well. Resuming the link also resumes the parent by construction.

BugLink: https://github.com/thesofproject/linux/issues/2606

- Better comments and commit messages.
- Modified the .prepare callback to only deal with the corner case that is
NOT covered today instead of systematically doing a full resume.

Pierre-Louis Bossart (3):
soundwire: intel: fix potential race condition during power down
soundwire: intel: skip suspend/resume/wake when link was not started
soundwire: intel: conditionally exit clock stop mode on system suspend

drivers/soundwire/intel.c | 150 ++++++++++++++++++++++++++++++--------
drivers/soundwire/intel.h | 1 +
2 files changed, 119 insertions(+), 32 deletions(-)