[PATCH v9 6/7] cpufreq: amd-pstate: introduce per CPU frequency boost control

[Perry Yuan <perry.yuan@amd.com>]

Add a new sysfs attribute file to support per CPU frequency boost
control, allowing individual CPUs to enable or disable CPB separately.

The new sysfs attribute file is located at below path,
`/sys/devices/system/cpu/cpuX/cpufreq/amd_pstate_boost_cpb`,
where `X` represents the CPU number.

To disable CPB for a specific CPU, you can use the following command:
$ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpuX/cpufreq/amd_pstate_boost_cpb"

After disabling CPB, the CPU frequency will no longer boost beyond
the base frequency for that particular CPU.

for example:
----------------------------------------------------------------------
CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ       MHZ
  0    0      0    0 0:0:0:0          yes 4208.0000 400.0000 1666.7740
  1    0      0    0 0:0:0:0          yes 4208.0000 400.0000  400.0000

----------------------------------------------------------------------
$ sudo bash -c "echo 0 > /sys/devices/system/cpu/cpu0/cpufreq/amd_pstate_boost_cpb"

CPU NODE SOCKET CORE L1d:L1i:L2:L3 ONLINE    MAXMHZ   MINMHZ       MHZ
  0    0      0    0 0:0:0:0          yes 3501.0000 400.0000 4154.3140
  1    0      0    0 0:0:0:0          yes 4208.0000 400.0000  400.0000

Please be aware that modifying the global variable
`amd_pstate_global_params.cpb_boost` will overwrite the individual CPU settings.

Signed-off-by: Perry Yuan <perry.yuan@amd.com>
---
 drivers/cpufreq/amd-pstate.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 11bce2c1db32..44531711a5fa 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1371,6 +1371,30 @@ static int amd_pstate_cpu_boost(int cpu, bool state)
 	return ret < 0 ? ret : 0;
 }
 
+static ssize_t show_amd_pstate_boost_cpb(struct cpufreq_policy *policy, char *buf)
+{
+	struct amd_cpudata *cpudata = policy->driver_data;
+	bool boost_val;
+
+	boost_val = READ_ONCE(cpudata->boost_state);
+
+	return sysfs_emit(buf, "%u\n", boost_val);
+}
+
+static ssize_t store_amd_pstate_boost_cpb(
+		struct cpufreq_policy *policy, const char *buf, size_t count)
+{
+	bool boost_val;
+	int ret;
+
+	if (sscanf(buf, "%d", &boost_val) != 1)
+		return -EINVAL;
+
+	ret = amd_pstate_cpu_boost(policy->cpu, boost_val);
+
+	return ret < 0 ? ret : count;
+}
+
 static ssize_t cpb_boost_show(struct device *dev,
 			   struct device_attribute *attr, char *buf)
 {
@@ -1416,6 +1440,7 @@ cpufreq_freq_attr_ro(amd_pstate_prefcore_ranking);
 cpufreq_freq_attr_ro(amd_pstate_hw_prefcore);
 cpufreq_freq_attr_rw(energy_performance_preference);
 cpufreq_freq_attr_ro(energy_performance_available_preferences);
+cpufreq_freq_attr_rw(amd_pstate_boost_cpb);
 static DEVICE_ATTR_RW(status);
 static DEVICE_ATTR_RO(prefcore);
 static DEVICE_ATTR_RW(cpb_boost);
@@ -1426,6 +1451,7 @@ static struct freq_attr *amd_pstate_attr[] = {
 	&amd_pstate_highest_perf,
 	&amd_pstate_prefcore_ranking,
 	&amd_pstate_hw_prefcore,
+	&amd_pstate_boost_cpb,
 	NULL,
 };
 
@@ -1437,6 +1463,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
 	&amd_pstate_hw_prefcore,
 	&energy_performance_preference,
 	&energy_performance_available_preferences,
+	&amd_pstate_boost_cpb,
 	NULL,
 };
 
-- 
2.34.1