On Thu, Nov 03, 2022 at 11:30:30AM -0700, Stephen Boyd wrote: > We shouldn't be calling runtime PM APIs from within the genpd > enable/disable path for a couple reasons. > > First, this causes an AA lockdep splat[1] because genpd can call into > genpd code again while holding the genpd lock. > Second, this confuses runtime PM on CoachZ for the camera devices by > causing the camera clock controller's runtime PM usage_count to go > negative after resuming from suspend. This is because runtime PM is > being used on the clock controller while runtime PM is disabled for the > device. > > The reason for the negative count is because a GDSC is represented as a > genpd and each genpd that is attached to a device is resumed during the > noirq phase of system wide suspend/resume (see the noirq suspend ops > assignment in pm_genpd_init() for more details). The camera GDSCs are > attached to camera devices with the 'power-domains' property in DT. > Every device has runtime PM disabled in the late system suspend phase > via __device_suspend_late(). Runtime PM is not usable until runtime PM > is enabled in device_resume_early(). The noirq phases run after the > 'late' and before the 'early' phase of suspend/resume. When the genpds > are resumed in genpd_resume_noirq(), we call down into gdsc_enable() > that calls pm_runtime_resume_and_get() and that returns -EACCES to > indicate failure to resume because runtime PM is disabled for all > devices. > > Upon closer inspection, calling runtime PM APIs like this in the GDSC > driver doesn't make sense. It was intended to make sure the GDSC for the > clock controller providing other GDSCs was enabled, specifically the > MMCX GDSC for the display clk controller on SM8250 (sm8250-dispcc), so > that GDSC register accesses succeeded. That will already happen because > we make the 'dev->pm_domain' a parent domain of each GDSC we register in > gdsc_register() via pm_genpd_add_subdomain(). When any of these GDSCs > are accessed, we'll enable the parent domain (in this specific case > MMCX). > > We also remove any getting of runtime PM during registration, because > when a genpd is registered it increments the count on the parent if the > genpd itself is already enabled. > > Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> > Cc: Johan Hovold <johan+linaro@xxxxxxxxxx> > Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx> > Cc: Taniya Das <quic_tdas@xxxxxxxxxxx> > Cc: Satya Priya <quic_c_skakit@xxxxxxxxxxx> > Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > Cc: Matthias Kaehlcke <mka@xxxxxxxxxxxx> > Reported-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> > Link: https://lore.kernel.org/r/CAE-0n52xbZeJ66RaKwggeRB57fUAwjvxGxfFMKOKJMKVyFTe+w@xxxxxxxxxxxxxx [1] > Fixes: 1b771839de05 ("clk: qcom: gdsc: enable optional power domain support") > Signed-off-by: Stephen Boyd <swboyd@xxxxxxxxxxxx> > --- > > Changes from v2 (https://lore.kernel.org/r/20221102170717.1262547-1-swboyd@xxxxxxxxxxxx): > * Drop dev assignment and remove struct member > * Update commit text, add link to report > > Changes from v1 (https://lore.kernel.org/r/20221101233421.997149-1-swboyd@xxxxxxxxxxxx): > * Fix ret thinko > * Update kerneldoc on 'dev' member Reviewed-by: Johan Hovold <johan+linaro@xxxxxxxxxx> Tested-by: Johan Hovold <johan+linaro@xxxxxxxxxx> Johan
