Patch "bnxt_en: Fix bnxt_refclk_read()" has been added to the 5.18-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    bnxt_en: Fix bnxt_refclk_read()

to the 5.18-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bnxt_en-fix-bnxt_refclk_read.patch
and it can be found in the queue-5.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit cf6794f66a76e793b7b8b43252ee7388ea117d1e
Author: Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx>
Date:   Mon Jul 11 22:26:18 2022 -0400

    bnxt_en: Fix bnxt_refclk_read()
    
    [ Upstream commit ddde5412fdaa5048bbca31529d46cb8da882870c ]
    
    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@xxxxxxxxx>
    Signed-off-by: Pavan Chebbi <pavan.chebbi@xxxxxxxxxxxx>
    Signed-off-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
index f9c94e5fe718..3221911e25fe 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
@@ -76,14 +76,23 @@ 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;
 }