On Tue, Apr 6, 2021 at 8:45 PM 'Saravana Kannan' via kernel-team <kernel-t...@android.com> wrote: > > Clocks can be turned on (by the hardware, bootloader, etc) upon a > reset/boot of a hardware platform. These "boot clocks" could be clocking > devices that are active before the kernel starts running. For example, > clocks needed for the interconnects, UART console, display, CPUs, DDR, > etc. > > When a boot clock is used by more than one consumer or multiple boot > clocks share a parent clock, the boot clock (or the common parent) can > be turned off when the first consumer probes. This can crash the device > or cause poor user experience. > > Fix this by explicitly enabling the boot clocks during clock > registration and then removing the enable vote when the clock provider > device gets its sync_state() callback. Since sync_state() callback comes > only when all the consumers of a device (not a specific clock) have > probed, this ensures the boot clocks are kept on at least until all > their consumers have had a chance to vote on them (in their respective > probe functions). > > Also, if a clock provider is loaded as a module and it has some boot > clocks, they get turned off only when a consumer explicitly turns them > off. So clocks that are boot clocks and are unused never get turned off > because the logic to turn off unused clocks has already run during > late_initcall_sync(). Adding sync_state() support also makes sure these > unused boot clocks are turned off once all the consumers have probed. > > Signed-off-by: Saravana Kannan <sarava...@google.com>
Hi Stephen, Gentle reminder. -Saravana > --- > drivers/clk/clk.c | 84 +++++++++++++++++++++++++++++++++++- > include/linux/clk-provider.h | 1 + > 2 files changed, 84 insertions(+), 1 deletion(-) > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > index d6301a3351f2..cd07f4d1254c 100644 > --- a/drivers/clk/clk.c > +++ b/drivers/clk/clk.c > @@ -72,6 +72,8 @@ struct clk_core { > unsigned long flags; > bool orphan; > bool rpm_enabled; > + bool need_sync; > + bool boot_enabled; > unsigned int enable_count; > unsigned int prepare_count; > unsigned int protect_count; > @@ -1215,6 +1217,15 @@ static void __init clk_unprepare_unused_subtree(struct > clk_core *core) > hlist_for_each_entry(child, &core->children, child_node) > clk_unprepare_unused_subtree(child); > > + /* > + * Orphan clocks might still not have their state held if one of their > + * ancestors hasn't been registered yet. We don't want to turn off > + * these orphan clocks now as they will be turned off later when their > + * device gets a sync_state() call. > + */ > + if (dev_has_sync_state(core->dev)) > + return; > + > if (core->prepare_count) > return; > > @@ -1246,6 +1257,15 @@ static void __init clk_disable_unused_subtree(struct > clk_core *core) > hlist_for_each_entry(child, &core->children, child_node) > clk_disable_unused_subtree(child); > > + /* > + * Orphan clocks might still not have their state held if one of their > + * ancestors hasn't been registered yet. We don't want to turn off > + * these orphan clocks now as they will be turned off later when their > + * device gets a sync_state() call. > + */ > + if (dev_has_sync_state(core->dev)) > + return; > + > if (core->flags & CLK_OPS_PARENT_ENABLE) > clk_core_prepare_enable(core->parent); > > @@ -1319,6 +1339,38 @@ static int __init clk_disable_unused(void) > } > late_initcall_sync(clk_disable_unused); > > +static void clk_unprepare_disable_dev_subtree(struct clk_core *core, > + struct device *dev) > +{ > + struct clk_core *child; > + > + lockdep_assert_held(&prepare_lock); > + > + hlist_for_each_entry(child, &core->children, child_node) > + clk_unprepare_disable_dev_subtree(child, dev); > + > + if (core->dev != dev || !core->need_sync) > + return; > + > + clk_core_disable_unprepare(core); > +} > + > +void clk_sync_state(struct device *dev) > +{ > + struct clk_core *core; > + > + clk_prepare_lock(); > + > + hlist_for_each_entry(core, &clk_root_list, child_node) > + clk_unprepare_disable_dev_subtree(core, dev); > + > + hlist_for_each_entry(core, &clk_orphan_list, child_node) > + clk_unprepare_disable_dev_subtree(core, dev); > + > + clk_prepare_unlock(); > +} > +EXPORT_SYMBOL_GPL(clk_sync_state); > + > static int clk_core_determine_round_nolock(struct clk_core *core, > struct clk_rate_request *req) > { > @@ -1725,6 +1777,30 @@ int clk_hw_get_parent_index(struct clk_hw *hw) > } > EXPORT_SYMBOL_GPL(clk_hw_get_parent_index); > > +static void clk_core_hold_state(struct clk_core *core) > +{ > + if (core->need_sync || !core->boot_enabled) > + return; > + > + if (core->orphan || !dev_has_sync_state(core->dev)) > + return; > + > + core->need_sync = !clk_core_prepare_enable(core); > +} > + > +static void __clk_core_update_orphan_hold_state(struct clk_core *core) > +{ > + struct clk_core *child; > + > + if (core->orphan) > + return; > + > + clk_core_hold_state(core); > + > + hlist_for_each_entry(child, &core->children, child_node) > + __clk_core_update_orphan_hold_state(child); > +} > + > /* > * Update the orphan status of @core and all its children. > */ > @@ -3392,6 +3468,7 @@ static void clk_core_reparent_orphans_nolock(void) > __clk_set_parent_after(orphan, parent, NULL); > __clk_recalc_accuracies(orphan); > __clk_recalc_rates(orphan, 0); > + __clk_core_update_orphan_hold_state(orphan); > } > } > } > @@ -3550,6 +3627,8 @@ static int __clk_core_init(struct clk_core *core) > rate = 0; > core->rate = core->req_rate = rate; > > + core->boot_enabled = clk_core_is_enabled(core); > + > /* > * Enable CLK_IS_CRITICAL clocks so newly added critical clocks > * don't get accidentally disabled when walking the orphan tree and > @@ -3572,6 +3651,7 @@ static int __clk_core_init(struct clk_core *core) > } > } > > + clk_core_hold_state(core); > clk_core_reparent_orphans_nolock(); > > > @@ -3837,8 +3917,10 @@ __clk_register(struct device *dev, struct device_node > *np, struct clk_hw *hw) > core->rpm_enabled = true; > core->dev = dev; > core->of_node = np; > - if (dev && dev->driver) > + if (dev && dev->driver) { > core->owner = dev->driver->owner; > + dev_set_drv_sync_state(dev, clk_sync_state); > + } > core->hw = hw; > core->flags = init->flags; > core->num_parents = init->num_parents; > diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h > index 58f6fe866ae9..429c413dadce 100644 > --- a/include/linux/clk-provider.h > +++ b/include/linux/clk-provider.h > @@ -1112,6 +1112,7 @@ void devm_clk_unregister(struct device *dev, struct clk > *clk); > > void clk_hw_unregister(struct clk_hw *hw); > void devm_clk_hw_unregister(struct device *dev, struct clk_hw *hw); > +void clk_sync_state(struct device *dev); > > /* helper functions */ > const char *__clk_get_name(const struct clk *clk); > -- > 2.31.1.295.g9ea45b61b8-goog > > -- > To unsubscribe from this group and stop receiving emails from it, send an > email to kernel-team+unsubscr...@android.com. >