From d8b35cfe97e1a54f1542da0e2e328108b7c9e32e Mon Sep 17 00:00:00 2001
From: Pavan Chebbi <pavan.chebbi@broadcom.com>
Date: Mon, 11 Jul 2022 22:26:18 -0400
Subject: [PATCH 09/28] bnxt_en: Fix bnxt_refclk_read()
Git-commit: ddde5412fdaa5048bbca31529d46cb8da882870c
Patch-mainline: v5.19-rc7
References: git-fixes

The upper 32-bit PHC register is not latched when reading the lower
32-bit PHC register.  Current code leaves a small window where we may
not read correct higher order bits if the lower order bits are just about
to wrap around.

This patch fixes this by reading higher order bits twice and makes
sure that final value is correctly paired with its lower 32 bits.

Fixes: 30e96f487f64 ("bnxt_en: Do not read the PTP PHC during chip reset")
Cc: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Denis Kirjanov <denis.kirjanov@suse.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
index 4eca32a29c9b..10f08a9a49c8 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
@@ -59,14 +59,23 @@ static int bnxt_refclk_read(struct bnxt *bp, struct ptp_system_timestamp *sts,
 			    u64 *ns)
 {
 	struct bnxt_ptp_cfg *ptp = bp->ptp_cfg;
+	u32 high_before, high_now, low;
 
 	if (test_bit(BNXT_STATE_IN_FW_RESET, &bp->state))
 		return -EIO;
 
+	high_before = readl(bp->bar0 + ptp->refclk_mapped_regs[1]);
 	ptp_read_system_prets(sts);
-	*ns = readl(bp->bar0 + ptp->refclk_mapped_regs[0]);
+	low = readl(bp->bar0 + ptp->refclk_mapped_regs[0]);
 	ptp_read_system_postts(sts);
-	*ns |= (u64)readl(bp->bar0 + ptp->refclk_mapped_regs[1]) << 32;
+	high_now = readl(bp->bar0 + ptp->refclk_mapped_regs[1]);
+	if (high_now != high_before) {
+		ptp_read_system_prets(sts);
+		low = readl(bp->bar0 + ptp->refclk_mapped_regs[0]);
+		ptp_read_system_postts(sts);
+	}
+	*ns = ((u64)high_now << 32) | low;
+
 	return 0;
 }
 
-- 
2.16.4