ptp: ocp: Improve PCIe delay estimation

The PCIe bus can be pretty busy during boot and probe function can see excessive delays. Let's find the minimal value out of several tests and use it as estimated value. Signed-off-by: Vadim Fedorenko <[email protected]> Link: https://patch.msgid.link/[email protected] Signed-off-by: Jakub Kicinski <[email protected]>
sirdarckcat · Sep 7, 2024 · aa05fe6 · aa05fe6
1 parent 9a95eed
commit aa05fe6
Showing 1 changed file with 11 additions and 9 deletions.
diff --git a/drivers/ptp/ptp_ocp.c b/drivers/ptp/ptp_ocp.c
@@ -1558,22 +1558,24 @@ ptp_ocp_watchdog(struct timer_list *t)
 static void
 ptp_ocp_estimate_pci_timing(struct ptp_ocp *bp)
 {
-	ktime_t start, end;
-	ktime_t delay;
+	ktime_t start, end, delay = U64_MAX;
 	u32 ctrl;
+	int i;
 
-	ctrl = ioread32(&bp->reg->ctrl);
-	ctrl = OCP_CTRL_READ_TIME_REQ | OCP_CTRL_ENABLE;
+	for (i = 0; i < 3; i++) {
+		ctrl = ioread32(&bp->reg->ctrl);
+		ctrl = OCP_CTRL_READ_TIME_REQ | OCP_CTRL_ENABLE;
 
-	iowrite32(ctrl, &bp->reg->ctrl);
+		iowrite32(ctrl, &bp->reg->ctrl);
 
-	start = ktime_get_ns();
+		start = ktime_get_raw_ns();
 
-	ctrl = ioread32(&bp->reg->ctrl);
+		ctrl = ioread32(&bp->reg->ctrl);
 
-	end = ktime_get_ns();
+		end = ktime_get_raw_ns();
 
-	delay = end - start;
+		delay = min(delay, end - start);
+	}
 	bp->ts_window_adjust = (delay >> 5) * 3;
 }