firewire: ohci: speed up PHY register accesses

Most PHY chips, when idle, can complete a register access in the time
needed for two or three PCI read transactions; bigger delays occur only
when data is currently being moved over the link/PHY interface.  So if
we busy-wait a few times when waiting for the register access to finish,
it is likely that we can finish without having to sleep.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index de5ff376231c..65b9bdb8541a 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -474,12 +474,17 @@ static int read_phy_reg(struct fw_ohci *ohci, int addr)
         int i;
 
         reg_write(ohci, OHCI1394_PhyControl, OHCI1394_PhyControl_Read(addr));
-        for (i = 0; i < 10; i++) {
+        for (i = 0; i < 3 + 100; i++) {
                 val = reg_read(ohci, OHCI1394_PhyControl);
                 if (val & OHCI1394_PhyControl_ReadDone)
                         return OHCI1394_PhyControl_ReadData(val);
 
-                msleep(1);
+                /*
+                 * Try a few times without waiting.  Sleeping is necessary
+                 * only when the link/PHY interface is busy.
+                 */
+                if (i >= 3)
+                        msleep(1);
         }
         fw_error("failed to read phy reg\n");
 
@@ -492,12 +497,13 @@ static int write_phy_reg(const struct fw_ohci *ohci, int addr, u32 val)
 
         reg_write(ohci, OHCI1394_PhyControl,
                   OHCI1394_PhyControl_Write(addr, val));
-        for (i = 0; i < 100; i++) {
+        for (i = 0; i < 3 + 100; i++) {
                 val = reg_read(ohci, OHCI1394_PhyControl);
                 if (!(val & OHCI1394_PhyControl_WritePending))
                         return 0;
 
-                msleep(1);
+                if (i >= 3)
+                        msleep(1);
         }
         fw_error("failed to write phy reg\n");