amd-pstate: Fix amd_pstate mode switch

amd_pstate mode can be changed by writing the mode name to the `status`
sysfs. But some combinations are not working. Fix this issue by taking
care of the edge cases.

Before the fix the mode change combination test fails:

 #./pst_test.sh
Test passed: from: disable, to
Test passed: from: disable, to disable
Test failed: 1, From mode: disable, to mode: passive
Test failed: 1, From mode: disable, to mode: active
Test failed: 1, From mode: passive, to mode: active
Test passed: from: passive, to disable
Test failed: 1, From mode: passive, to mode: passive
Test failed: 1, From mode: passive, to mode: active
Test failed: 1, From mode: active, to mode: active
Test passed: from: active, to disable
Test failed: 1, From mode: active, to mode: passive
Test failed: 1, From mode: active, to mode: active

After the fix test passes:

 #./pst_test.sh
Test passed: from: disable, to
Test passed: from: disable, to disable
Test passed: from: disable, to passive
Test passed: from: disable, to active
Test passed: from: passive, to active
Test passed: from: passive, to disable
Test passed: from: passive, to passive
Test passed: from: passive, to active
Test passed: from: active, to active
Test passed: from: active, to disable
Test passed: from: active, to passive
Test passed: from: active, to active

Fixes: abd61c08ef349 ("cpufreq: amd-pstate: add driver working mode switch support")
Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 73c7643..8dd46fa 100644 (file)
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -840,22 +840,20 @@ static int amd_pstate_update_status(const char *buf, size_t size)
 
        switch(mode_idx) {
        case AMD_PSTATE_DISABLE:
-               if (!current_pstate_driver)
-                       return -EINVAL;
-               if (cppc_state == AMD_PSTATE_ACTIVE)
-                       return -EBUSY;
-               cpufreq_unregister_driver(current_pstate_driver);
-               amd_pstate_driver_cleanup();
+               if (current_pstate_driver) {
+                       cpufreq_unregister_driver(current_pstate_driver);
+                       amd_pstate_driver_cleanup();
+               }
                break;
        case AMD_PSTATE_PASSIVE:
                if (current_pstate_driver) {
                        if (current_pstate_driver == &amd_pstate_driver)
                                return 0;
                        cpufreq_unregister_driver(current_pstate_driver);
-                       cppc_state = AMD_PSTATE_PASSIVE;
-                       current_pstate_driver = &amd_pstate_driver;
                }
 
+               current_pstate_driver = &amd_pstate_driver;
+               cppc_state = AMD_PSTATE_PASSIVE;
                ret = cpufreq_register_driver(current_pstate_driver);
                break;
        case AMD_PSTATE_ACTIVE:
@@ -863,10 +861,10 @@ static int amd_pstate_update_status(const char *buf, size_t size)
                        if (current_pstate_driver == &amd_pstate_epp_driver)
                                return 0;
                        cpufreq_unregister_driver(current_pstate_driver);
-                       current_pstate_driver = &amd_pstate_epp_driver;
-                       cppc_state = AMD_PSTATE_ACTIVE;
                }
 
+               current_pstate_driver = &amd_pstate_epp_driver;
+               cppc_state = AMD_PSTATE_ACTIVE;
                ret = cpufreq_register_driver(current_pstate_driver);
                break;
        default: