diff mbox series

[v2,06/11] xen/cpufreq: only set gov NULL when cpufreq_driver.setpolicy is NULL

Message ID 20250206083255.1296363-7-Penny.Zheng@amd.com (mailing list archive)
State New
Headers show
Series amd-cppc CPU Performance Scaling Driver | expand

Commit Message

Penny, Zheng Feb. 6, 2025, 8:32 a.m. UTC 
From: Penny Zheng <penny.zheng@amd.com>

amd-cppc on active mode bypasses the scaling governor layer, and
provides its own P-state selection algorithms in hardware. Consequently,
when it is used, the driver's -> setpolicy() callback is invoked
to register per-CPU utilization update callbacks, not the ->target()
callback.

So, only when cpufreq_driver.setpolicy is NULL, we need to deliberately
set old gov as NULL to trigger the according gov starting.

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
---
v1 -> v2:
- Change condition check to .setpolicy being NULL
---
 xen/drivers/cpufreq/cpufreq.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Comments

Jan Beulich Feb. 12, 2025, 3:38 p.m. UTC | #1 
On 06.02.2025 09:32, Penny Zheng wrote:
> From: Penny Zheng <penny.zheng@amd.com>
> 
> amd-cppc on active mode bypasses the scaling governor layer, and
> provides its own P-state selection algorithms in hardware. Consequently,
> when it is used, the driver's -> setpolicy() callback is invoked
> to register per-CPU utilization update callbacks, not the ->target()
> callback.
> 
> So, only when cpufreq_driver.setpolicy is NULL, we need to deliberately
> set old gov as NULL to trigger the according gov starting.
> 
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
diff mbox series

Patch

diff --git a/xen/drivers/cpufreq/cpufreq.c b/xen/drivers/cpufreq/cpufreq.c
index c0c6dc4c42..860ae32c8a 100644
--- a/xen/drivers/cpufreq/cpufreq.c
+++ b/xen/drivers/cpufreq/cpufreq.c
@@ -317,7 +317,13 @@  int cpufreq_add_cpu(unsigned int cpu)
     if (hw_all || (cpumask_weight(cpufreq_dom->map) ==
                    perf->domain_info.num_processors)) {
         memcpy(&new_policy, policy, sizeof(struct cpufreq_policy));
-        policy->governor = NULL;
+
+       /*
+        * Only when cpufreq_driver.setpolicy == NULL, we need to deliberately
+        * set old gov as NULL to trigger the according gov starting.
+        */
+       if ( cpufreq_driver.setpolicy == NULL )
+            policy->governor = NULL;
 
         cpufreq_cmdline_common_para(&new_policy);