linux-kernel - [PATCH] cpufreq: dt: check the error returned by dev_pm_opp_of_cpumask_add

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Message-Id: <20210325043129.2255918-1-quanyang.wang@windriver.com>
Date:   Thu, 25 Mar 2021 12:31:29 +0800
From:   quanyang.wang@...driver.com
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Quanyang Wang <quanyang.wang@...driver.com>
Subject: [PATCH] cpufreq: dt: check the error returned by dev_pm_opp_of_cpumask_add_table

From: Quanyang Wang <quanyang.wang@...driver.com>

The function dev_pm_opp_of_cpumask_add_table may return zero or an
error. When it returns an error, this means that no OPP table is
added for the cpumask because _dev_pm_opp_cpumask_remove_table is
called to free all OPPs associated with the cpu devices in the error
label "remove_table". So continuing to run the next function
dev_pm_opp_get_opp_count is meaningless since it always return the
count value as 0.

There is another reason why we should check the error returned by
dev_pm_opp_of_cpumask_add_table is that it may return -EPROBE_DEFER
which comes from clk_get(dev, NULL) in _update_opp_table_clk. When
the clk for cpu device isn't ready, dt_cpufreq_probe should be deferred
and wait to be called again. But if we ignore the return error of
dev_pm_opp_of_cpumask_add_table, dt_cpufreq_probe will return -ENODEV
because dev_pm_opp_get_opp_count returns the count value as 0,
the cpufreq-dt driver will fail with the error log as below:

[    0.724069] cpu cpu0: OPP table can't be empty

Signed-off-by: Quanyang Wang <quanyang.wang@...driver.com>
---
 drivers/cpufreq/cpufreq-dt.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/cpufreq/cpufreq-dt.c b/drivers/cpufreq/cpufreq-dt.c
index b1e1bdc63b01..f24359f47b1a 100644
--- a/drivers/cpufreq/cpufreq-dt.c
+++ b/drivers/cpufreq/cpufreq-dt.c
@@ -255,10 +255,16 @@ static int dt_cpufreq_early_init(struct device *dev, int cpu)
 	 * before updating priv->cpus. Otherwise, we will end up creating
 	 * duplicate OPPs for the CPUs.
 	 *
-	 * OPPs might be populated at runtime, don't check for error here.
+	 * We need check the return value here, if it is non-zero, there is
+	 * need to go on.
 	 */
-	if (!dev_pm_opp_of_cpumask_add_table(priv->cpus))
-		priv->have_static_opps = true;
+	ret = dev_pm_opp_of_cpumask_add_table(priv->cpus);
+	if (ret) {
+		dev_err(cpu_dev, "Failed to add OPP table for CPUs\n");
+		goto out;
+	}
+
+	priv->have_static_opps = true;

 	/*
 	 * The OPP table must be initialized, statically or dynamically, by this
-- 
2.25.1