[ Upstream commit d470be3c4f ]
The pm_runtime usage in lpass-sc7280 was broken in quite a few
ways. Specifically:
1. At the end of probe it called "put" twice. This is a no-no and will
end us up with a negative usage count. Even worse than calling
"put" twice, it never called "get" once. Thus after bootup it could
be seen that the runtime usage of the devices managed by this
driver was -2.
2. In some error cases it manually called pm_runtime_disable() even
though it had previously used devm_add_action_or_reset() to set
this up to be called automatically. This meant that in these error
cases we'd double-call pm_runtime_disable().
3. It forgot to call undo pm_runtime_use_autosuspend(), which can
sometimes have subtle problems (and the docs specifically mention
that you need to undo this function).
Overall the above seriously calls into question how this driver is
working. It seems like a combination of "it doesn't", "by luck", and
"because of the weirdness of runtime_pm". Specifically I put a
printout to the serial console every time the runtime suspend/resume
was called for the two devices created by this driver (I wrapped the
pm_clk calls). When I had serial console enabled, I found that the
calls got resumed at bootup (when the clk core probed and before our
double-put) and then never touched again. That's no good.
[ 0.829997] DOUG: my_pm_clk_resume, usage=1
[ 0.835487] DOUG: my_pm_clk_resume, usage=1
When I disabled serial console (speeding up boot), I got a different
pattern, which I guess (?) is better:
[ 0.089767] DOUG: my_pm_clk_resume, usage=1
[ 0.090507] DOUG: my_pm_clk_resume, usage=1
[ 0.151885] DOUG: my_pm_clk_suspend, usage=-2
[ 0.151914] DOUG: my_pm_clk_suspend, usage=-2
[ 1.825747] DOUG: my_pm_clk_resume, usage=-1
[ 1.825774] DOUG: my_pm_clk_resume, usage=-1
[ 1.888269] DOUG: my_pm_clk_suspend, usage=-2
[ 1.888282] DOUG: my_pm_clk_suspend, usage=-2
These different patterns have to do with the fact that the core PM
Runtime code really isn't designed to be robust to negative usage
counts and sometimes may happen to stumble upon a behavior that
happens to "work". For instance, you can see that
__pm_runtime_suspend() will treat any non-zero value (including
negative numbers) as if the device is in use.
In any case, let's fix the driver to be correct. We'll hold a
pm_runtime reference for the whole probe and then drop it (once!) at
the end. We'll get rid of manual pm_runtime_disable() calls in the
error handling. We'll also switch to devm_pm_runtime_enable(), which
magically handles undoing pm_runtime_use_autosuspend() as of commit
b4060db925 ("PM: runtime: Have devm_pm_runtime_enable() handle
pm_runtime_dont_use_autosuspend()").
While we're at this, let's also use devm_pm_clk_create() instead of
rolling it ourselves.
Note that the above changes make it obvious that
lpassaudio_create_pm_clks() was doing more than just creating
clocks. It was also setting up pm_runtime parameters. Let's rename it.
All of these problems were found by code inspection. I started looking
at this driver because it was involved in a deadlock that I reported a
while ago [1]. Though I bisected the deadlock to commit 1b771839de
("clk: qcom: gdsc: enable optional power domain support"), it was
never really clear why that patch affected it other than a luck of
timing changes. I'll also note that by fixing the timing (as done in
this change) we also seem to aboid the deadlock, which is a nice
benefit.
Also note that some of the fixes here are much the same type of stuff
that Dmitry did in commit 72cfc73f46 ("clk: qcom: use
devm_pm_runtime_enable and devm_pm_clk_create"), but I guess
lpassaudiocc-sc7280.c didn't exist then.
[1] https://lore.kernel.org/r/20220922154354.2486595-1-dianders@chromium.org
Fixes: a9dd26639d ("clk: qcom: lpass: Add support for LPASS clock controller for SC7280")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221104064055.1.I00a0e4564a25489e85328ec41636497775627564@changeid
Signed-off-by: Sasha Levin <sashal@kernel.org>
607ccb7d3d