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>
diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index de5ff37..65b9bdb 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -474,12 +474,17 @@
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 @@
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");