[PATCH 4/5 V4] PCI: only return true when dev io state is really changed

[Ethan Zhao]

When uncorrectable error happens, AER driver and DPC driver interrupt
handlers likely call

   pcie_do_recovery()
   ->pci_walk_bus()
     ->report_frozen_detected()

with pci_channel_io_frozen the same time.
   If pci_dev_set_io_state() return true even if the original state is
pci_channel_io_frozen, that will cause AER or DPC handler re-enter
the error detecting and recovery procedure one after another.
   The result is the recovery flow mixed between AER and DPC.
So simplify the pci_dev_set_io_state() function to only return true
when dev->error_state is changed.

Signed-off-by: Ethan Zhao <haifeng.z...@intel.com>
Tested-by: Wen Jin <wen....@intel.com>
Tested-by: Shanshan Zhang <shanshanx.zh...@intel.com>
Reviewed-by: Alexandru Gagniuc <mr.nuke...@gmail.com>
---
Changnes:
 V2: revise description and code according to suggestion from Andy.
 V3: change code to simpler.
 V4: no change.
 V5: no change.
 
 drivers/pci/pci.h | 37 +++++--------------------------------
 1 file changed, 5 insertions(+), 32 deletions(-)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index fa12f7cbc1a0..a2c1c7d5f494 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -359,39 +359,12 @@ struct pci_sriov {
 static inline bool pci_dev_set_io_state(struct pci_dev *dev,
                                        pci_channel_state_t new)
 {
-       bool changed = false;
-
        device_lock_assert(&dev->dev);
-       switch (new) {
-       case pci_channel_io_perm_failure:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-               case pci_channel_io_perm_failure:
-                       changed = true;
-                       break;
-               }
-               break;
-       case pci_channel_io_frozen:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-                       changed = true;
-                       break;
-               }
-               break;
-       case pci_channel_io_normal:
-               switch (dev->error_state) {
-               case pci_channel_io_frozen:
-               case pci_channel_io_normal:
-                       changed = true;
-                       break;
-               }
-               break;
-       }
-       if (changed)
-               dev->error_state = new;
-       return changed;
+       if (dev->error_state == new)
+               return false;
+
+       dev->error_state = new;
+       return true;
 }
 
 static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
-- 
2.18.4