[v6] amd-cppc CPU Performance Scaling Driver

[PATCH v6 04/19] x86/cpufreq: continue looping other than -EBUSY or successful return

Posted by Penny Zheng 3 months, 3 weeks ago

Right now, only when we failed cpufreq driver registration with -ENODEV, we get
the chance to try the fallback option.
There are two code path erroring out other than -ENODEV in cpufreq driver
registration: one is when the driver itself is broken, like missing mandatory
hooks, cpufreq_register_driver() will fail with -EINVAL, in which we shall
be able to try the fallback option, and the other is -EBUSY due to repeated
registration, in which we shall just exit the loop.

So in conclusion, when error code is -EBUSY or successful return, both
indicating a proper driver is already registered, we shall bail the loop,
other than that, we shall continue to try the fallback option.

Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>
---
v5 -> v6:
- new commit
---
 xen/arch/x86/acpi/cpufreq/cpufreq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/xen/arch/x86/acpi/cpufreq/cpufreq.c b/xen/arch/x86/acpi/cpufreq/cpufreq.c
index 61e98b67bd..45f301f354 100644
--- a/xen/arch/x86/acpi/cpufreq/cpufreq.c
+++ b/xen/arch/x86/acpi/cpufreq/cpufreq.c
@@ -150,7 +150,7 @@ static int __init cf_check cpufreq_driver_init(void)
                     break;
                 }
 
-                if ( ret != -ENODEV )
+                if ( !ret || ret == -EBUSY )
                     break;
             }
             break;
-- 
2.34.1

Re: [PATCH v6 04/19] x86/cpufreq: continue looping other than -EBUSY or successful return

Posted by Jan Beulich 3 months, 2 weeks ago

On 11.07.2025 05:50, Penny Zheng wrote:
> Right now, only when we failed cpufreq driver registration with -ENODEV, we get
> the chance to try the fallback option.
> There are two code path erroring out other than -ENODEV in cpufreq driver
> registration: one is when the driver itself is broken, like missing mandatory
> hooks, cpufreq_register_driver() will fail with -EINVAL, in which we shall
> be able to try the fallback option, and the other is -EBUSY due to repeated
> registration, in which we shall just exit the loop.
> 
> So in conclusion, when error code is -EBUSY or successful return, both
> indicating a proper driver is already registered, we shall bail the loop,
> other than that, we shall continue to try the fallback option.
> 
> Signed-off-by: Penny Zheng <Penny.Zheng@amd.com>

Reviewed-by: Jan Beulich <jbeulich@suse.com>
(and perhaps also a Reported-by: or Suggested-by: ...)