firewire: ohci: do not clear PHY interrupt status inadvertently

The interrupt status bits in PHY register 5 are cleared by writing a one
bit.  To avoid clearing them unadvertently, do not write them back when
they were read as set, but only when they have been explicitly requested
to be set.

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

2 files changed, 8 insertions, 0 deletions

diff --git a/drivers/firewire/core.h b/drivers/firewire/core.h
index fb0321300cc..b2a7b651473 100644
--- a/drivers/firewire/core.h
+++ b/drivers/firewire/core.h
@@ -28,6 +28,7 @@ struct fw_packet;
 #define PHY_CONTENDER           0x40
 #define PHY_BUS_RESET           0x40
 #define PHY_BUS_SHORT_RESET     0x40
+#define PHY_INT_STATUS_BITS     0x3c
 
 #define BANDWIDTH_AVAILABLE_INITIAL     4915
 #define BROADCAST_CHANNEL_INITIAL       (1 << 31 | 31)
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 8ebccda94df..525848f71c3 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -490,6 +490,13 @@ static int ohci_update_phy_reg(struct fw_card *card, int addr,
         if (err < 0)
                 return err;
 
+        /*
+         * The interrupt status bits are cleared by writing a one bit.
+         * Avoid clearing them unless explicitly requested in set_bits.
+         */
+        if (addr == 5)
+                clear_bits |= PHY_INT_STATUS_BITS;
+
         old = (old & ~clear_bits) | set_bits;
         reg_write(ohci, OHCI1394_PhyControl,
                   OHCI1394_PhyControl_Write(addr, old));