firewire: ohci: wait for local CSR lock access to finish

Add a loop to wait for the controller to finish a locally-initiated CSR
lock operation.  Google shows some occurrences of the "swap not done
yet" message which might indicate that some OHCI controllers are not
fast enough to do the lock/swap in the time needed for one PCI access.

This also correctly handles the case where the lock operation did not
finish, instead of silently returning an uninitialized value.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 13 insertions, 7 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 82fb2e7e99ef..6e95f8fb56db 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -1158,7 +1158,7 @@ static void handle_local_lock(struct fw_ohci *ohci,
                               struct fw_packet *packet, u32 csr)
 {
         struct fw_packet response;
-        int tcode, length, ext_tcode, sel;
+        int tcode, length, ext_tcode, sel, try;
         __be32 *payload, lock_old;
         u32 lock_arg, lock_data;
 
@@ -1185,13 +1185,19 @@ static void handle_local_lock(struct fw_ohci *ohci,
         reg_write(ohci, OHCI1394_CSRCompareData, lock_arg);
         reg_write(ohci, OHCI1394_CSRControl, sel);
 
-        if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000)
-                lock_old = cpu_to_be32(reg_read(ohci, OHCI1394_CSRData));
-        else
-                fw_notify("swap not done yet\n");
+        for (try = 0; try < 20; try++)
+                if (reg_read(ohci, OHCI1394_CSRControl) & 0x80000000) {
+                        lock_old = cpu_to_be32(reg_read(ohci,
+                                                        OHCI1394_CSRData));
+                        fw_fill_response(&response, packet->header,
+                                         RCODE_COMPLETE,
+                                         &lock_old, sizeof(lock_old));
+                        goto out;
+                }
+
+        fw_error("swap not done (CSR lock timeout)\n");
+        fw_fill_response(&response, packet->header, RCODE_BUSY, NULL, 0);
 
-        fw_fill_response(&response, packet->header,
-                         RCODE_COMPLETE, &lock_old, sizeof(lock_old));
  out:
         fw_core_handle_response(&ohci->card, &response);
 }