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@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: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
index 62a931de5b1a74d0037ee6eb94a87478bbf0d9b8..a78cc65a38f2f7734193280096dbd0af15dc41f5 100644 (file)
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
@@ -61,14 +61,23 @@ 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;
 }