[PATCH 07/13] powerpc/eeh: Clean up pci_ers_result handling

[Sam Bobroff]

As EEH event handling progresses, a cumulative result of type
pci_ers_result is built up by (some of) the eeh_report_*() functions
using either:
        if (rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
        if (*res == PCI_ERS_RESULT_NONE) *res = rc;
or:
        if ((*res == PCI_ERS_RESULT_NONE) ||
            (*res == PCI_ERS_RESULT_RECOVERED)) *res = rc;
        if (*res == PCI_ERS_RESULT_DISCONNECT &&
            rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
(Where *res is the accumulator.)

However, the intent is not immediately clear and the result in some
situations is order dependent.

Address this by assigning a priority to each result value, and always
merging to the highest priority. This renders the intent clear, and
provides a stable value for all orderings.

Signed-off-by: Sam Bobroff <sbobr...@linux.ibm.com>
---
 arch/powerpc/kernel/eeh_driver.c | 36 ++++++++++++++++++++++++++----------
 1 file changed, 26 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/eeh_driver.c b/arch/powerpc/kernel/eeh_driver.c
index 188d15c4fe3a..f33dd68a9ca2 100644
--- a/arch/powerpc/kernel/eeh_driver.c
+++ b/arch/powerpc/kernel/eeh_driver.c
@@ -39,6 +39,29 @@ struct eeh_rmv_data {
        int removed;
 };
 
+static int eeh_result_priority(enum pci_ers_result result)
+{
+       switch (result) {
+       case PCI_ERS_RESULT_NONE: return 0;
+       case PCI_ERS_RESULT_NO_AER_DRIVER: return 1;
+       case PCI_ERS_RESULT_RECOVERED: return 2;
+       case PCI_ERS_RESULT_CAN_RECOVER: return 3;
+       case PCI_ERS_RESULT_DISCONNECT: return 4;
+       case PCI_ERS_RESULT_NEED_RESET: return 5;
+       default:
+               WARN_ONCE(1, "Unknown pci_ers_result value");
+               return 0;
+       }
+};
+
+static enum pci_ers_result merge_result(enum pci_ers_result old,
+                                       enum pci_ers_result new)
+{
+       if (eeh_result_priority(new) > eeh_result_priority(old))
+               return new;
+       return old;
+}
+
 /**
  * eeh_pcid_get - Get the PCI device driver
  * @pdev: PCI device
@@ -206,9 +229,7 @@ static void *eeh_report_error(struct eeh_dev *edev, void 
*userdata)
 
        rc = driver->err_handler->error_detected(dev, pci_channel_io_frozen);
 
-       /* A driver that needs a reset trumps all others */
-       if (rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
-       if (*res == PCI_ERS_RESULT_NONE) *res = rc;
+       *res = merge_result(*res, rc);
 
        edev->in_error = true;
        pci_uevent_ers(dev, PCI_ERS_RESULT_NONE);
@@ -249,9 +270,7 @@ static void *eeh_report_mmio_enabled(struct eeh_dev *edev, 
void *userdata)
 
        rc = driver->err_handler->mmio_enabled(dev);
 
-       /* A driver that needs a reset trumps all others */
-       if (rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
-       if (*res == PCI_ERS_RESULT_NONE) *res = rc;
+       *res = merge_result(*res, rc);
 
 out:
        eeh_pcid_put(dev);
@@ -294,10 +313,7 @@ static void *eeh_report_reset(struct eeh_dev *edev, void 
*userdata)
                goto out;
 
        rc = driver->err_handler->slot_reset(dev);
-       if ((*res == PCI_ERS_RESULT_NONE) ||
-           (*res == PCI_ERS_RESULT_RECOVERED)) *res = rc;
-       if (*res == PCI_ERS_RESULT_DISCONNECT &&
-            rc == PCI_ERS_RESULT_NEED_RESET) *res = rc;
+       *res = merge_result(*res, rc);
 
 out:
        eeh_pcid_put(dev);
-- 
2.16.1.74.g9b0b1f47b