On 18-01-21, 21:35, Dmitry Osipenko wrote:

18.01.2021 11:20, Viresh Kumar пишет:

quoted

quoted

+int dev_pm_opp_sync_regulators(struct device *dev)
+{
+	struct opp_table *opp_table;
+	struct regulator *reg;
+	int i, ret = 0;
+
+	/* Device may not have OPP table */
+	opp_table = _find_opp_table(dev);
+	if (IS_ERR(opp_table))
+		return 0;
+
+	/* Regulator may not be required for the device */
+	if (!opp_table->regulators)
+		goto put_table;
+
+	mutex_lock(&opp_table->lock);

What exactly do you need this lock for ?

It is needed for protecting simultaneous invocations of
dev_pm_opp_sync_regulators() and dev_pm_opp_set_voltage().

The sync_regulators() should be invoked only after completion of the
set_voltage() in a case of Tegra power domain driver since potentially
both could be running in parallel. For example device driver may be
changing performance state in a work thread, while PM domain state is
syncing.

I think just checking the 'enabled' flag should be enough here (you may need a
lock for it though, but the lock should cover only the area it is supposed to
cover and nothing else.

But maybe it will be better to move the protection to the PM driver
since we're focused on sync_regulators() and set_voltage() here, but
there are other OPP API functions which use regulators. I'll need to
take a closer look at it.

-- 
viresh