Re: [PATCH] cpufreq/amd-pstate: Fix amd_pstate mode switch on shared memory systems

From: Mario Limonciello
Date: Mon Oct 07 2024 - 12:32:00 EST


On 10/4/2024 07:23, Dhananjay Ugwekar wrote:
While switching the driver mode between active and passive, Collaborative
Processor Performance Control (CPPC) is disabled in
amd_pstate_unregister_driver(). But, it is not enabled back while registering
the new driver (passive or active). This leads to the new driver mode not
working correctly, so enable it back in amd_pstate_register_driver().

Fixes: 3ca7bc818d8c ("cpufreq: amd-pstate: Add guided mode control support via sysfs")
Signed-off-by: Dhananjay Ugwekar <Dhananjay.Ugwekar@xxxxxxx>

Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxx>

I think as a minimally risky fix to go to 6.12-rcX this makes sense, but looking at all this code there is a bit of duplication that exists that we should do a more general cleanup for 6.13.

So I'll queue this up in my -fixes branch for 6.12-rcX. but please do the bigger cleanup as a follow up that we can land for 6.13.

---
drivers/cpufreq/amd-pstate.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index cdc08d2ddd52..4acf5fbeb116 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1191,11 +1191,21 @@ static int amd_pstate_register_driver(int mode)
return -EINVAL;
cppc_state = mode;
+
+ ret = amd_pstate_enable(true);
+ if (ret) {
+ pr_err("failed to enable cppc during amd-pstate driver registration, return %d\n",
+ ret);
+ amd_pstate_driver_cleanup();
+ return ret;
+ }
+
ret = cpufreq_register_driver(current_pstate_driver);
if (ret) {
amd_pstate_driver_cleanup();
return ret;
}
+
return 0;
}