[PATCH 6.1.y] cpufreq: amd-pstate: Add ->fast_switch() callback

[Wyes Karny <wyes.karny@amd.com>]

From: "Gautham R. Shenoy" <gautham.shenoy@amd.com>

[ Upstream commit 4badf2eb1e986bdbf34dd2f5d4c979553a86fe54 ]

Schedutil normally calls the adjust_perf callback for drivers with
adjust_perf callback available and fast_switch_possible flag set.
However, when frequency invariance is disabled and schedutil tries to
invoke fast_switch. So, there is a chance of kernel crash if this
function pointer is not set. To protect against this scenario add
fast_switch callback to amd_pstate driver.

Fixes: 1d215f0319c2 ("cpufreq: amd-pstate: Add fast switch function for AMD P-State")
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 4badf2eb1e986bdbf34dd2f5d4c979553a86fe54)
---
 drivers/cpufreq/amd-pstate.c | 37 +++++++++++++++++++++++++++++-------
 1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index c17bd845f5fc..446edc0fd192 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -249,9 +249,8 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy)
 	return 0;
 }
 
-static int amd_pstate_target(struct cpufreq_policy *policy,
-			     unsigned int target_freq,
-			     unsigned int relation)
+static int amd_pstate_update_freq(struct cpufreq_policy *policy,
+				  unsigned int target_freq, bool fast_switch)
 {
 	struct cpufreq_freqs freqs;
 	struct amd_cpudata *cpudata = policy->driver_data;
@@ -270,14 +269,36 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
 	des_perf = DIV_ROUND_CLOSEST(target_freq * cap_perf,
 				     cpudata->max_freq);
 
-	cpufreq_freq_transition_begin(policy, &freqs);
-	amd_pstate_update(cpudata, min_perf, des_perf,
-			  max_perf, false);
-	cpufreq_freq_transition_end(policy, &freqs, false);
+	WARN_ON(fast_switch && !policy->fast_switch_enabled);
+	/*
+	 * If fast_switch is desired, then there aren't any registered
+	 * transition notifiers. See comment for
+	 * cpufreq_enable_fast_switch().
+	 */
+	if (!fast_switch)
+		cpufreq_freq_transition_begin(policy, &freqs);
+
+	amd_pstate_update(cpudata, min_perf, des_perf, max_perf, fast_switch);
+
+	if (!fast_switch)
+		cpufreq_freq_transition_end(policy, &freqs, false);
 
 	return 0;
 }
 
+static int amd_pstate_target(struct cpufreq_policy *policy,
+			     unsigned int target_freq,
+			     unsigned int relation)
+{
+	return amd_pstate_update_freq(policy, target_freq, false);
+}
+
+static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy,
+				  unsigned int target_freq)
+{
+	return amd_pstate_update_freq(policy, target_freq, true);
+}
+
 static void amd_pstate_adjust_perf(unsigned int cpu,
 				   unsigned long _min_perf,
 				   unsigned long target_perf,
@@ -517,6 +538,7 @@ static int amd_pstate_cpu_exit(struct cpufreq_policy *policy)
 
 	freq_qos_remove_request(&cpudata->req[1]);
 	freq_qos_remove_request(&cpudata->req[0]);
+	policy->fast_switch_possible = false;
 	kfree(cpudata);
 
 	return 0;
@@ -608,6 +630,7 @@ static struct cpufreq_driver amd_pstate_driver = {
 	.flags		= CPUFREQ_CONST_LOOPS | CPUFREQ_NEED_UPDATE_LIMITS,
 	.verify		= amd_pstate_verify,
 	.target		= amd_pstate_target,
+	.fast_switch    = amd_pstate_fast_switch,
 	.init		= amd_pstate_cpu_init,
 	.exit		= amd_pstate_cpu_exit,
 	.suspend	= amd_pstate_cpu_suspend,
-- 
2.34.1