[PATCH] cpufreq: Fix policy initialization for internal governor drivers

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

Before commit 1e4f63aecb53 ("cpufreq: Avoid creating excessively
large stack frames") the initial value of the policy field in struct
cpufreq_policy set by the driver's ->init() callback was implicitly
passed from cpufreq_init_policy() to cpufreq_set_policy() if the
default governor was neither "performance" nor "powersave".  After
that commit, however, cpufreq_init_policy() must take that case into
consideration explicitly and handle it as appropriate, so make that
happen.

Fixes: 1e4f63aecb53 ("cpufreq: Avoid creating excessively large stack frames")
Link: https://lore.kernel.org/linux-pm/39fb762880c27da110086741315ca8b111d781cd.camel@xxxxxxxxx/
Reported-by: Artem Bityutskiy <dedekind1@xxxxxxxxx>
Cc: 5.4+ <stable@xxxxxxxxxxxxxxx> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---

Note that I'm going to fast-track this patch for 5.6-rc4 which means that
it will go into my linux-next branch as soon as it shows up in the lists.

Thanks and sorry for the breakage!

---
 drivers/cpufreq/cpufreq.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/cpufreq/cpufreq.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/cpufreq.c
+++ linux-pm/drivers/cpufreq/cpufreq.c
@@ -1076,9 +1076,17 @@ static int cpufreq_init_policy(struct cp
 			pol = policy->last_policy;
 		} else if (def_gov) {
 			pol = cpufreq_parse_policy(def_gov->name);
-		} else {
-			return -ENODATA;
+			/*
+			 * In case the default governor is neiter "performance"
+			 * nor "powersave", fall back to the initial policy
+			 * value set by the driver.
+			 */
+			if (pol == CPUFREQ_POLICY_UNKNOWN)
+				pol = policy->policy;
 		}
+		if (pol != CPUFREQ_POLICY_PERFORMANCE &&
+		    pol != CPUFREQ_POLICY_POWERSAVE)
+			return -ENODATA;
 	}
 
 	return cpufreq_set_policy(policy, gov, pol);