linux-kernel - [PATCH net-next v6 4/6] ptp: clockmatrix: dco input-to-output delay is 20 FOD cycles + 8ns

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Message-ID: <PH7PR03MB7064A9C11FB1252AEED5EF13A082A@PH7PR03MB7064.namprd03.prod.outlook.com>
Date:   Thu, 30 Nov 2023 13:46:32 -0500
From:   Min Li <lnimi@...mail.com>
To:     richardcochran@...il.com, lee@...nel.org
Cc:     linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Min Li <min.li.xe@...esas.com>
Subject: [PATCH net-next v6 4/6] ptp: clockmatrix: dco input-to-output delay is 20 FOD cycles + 8ns

From: Min Li <min.li.xe@...esas.com>

Signed-off-by: Min Li <min.li.xe@...esas.com>
---
 drivers/ptp/ptp_clockmatrix.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ptp/ptp_clockmatrix.c b/drivers/ptp/ptp_clockmatrix.c
index d069b6e451ef..21f3a2c179f5 100644
--- a/drivers/ptp/ptp_clockmatrix.c
+++ b/drivers/ptp/ptp_clockmatrix.c
@@ -2165,7 +2165,7 @@ static int configure_channel_pll(struct idtcm_channel *channel)
 
 /*
  * Compensate for the PTP DCO input-to-output delay.
- * This delay is 18 FOD cycles.
+ * This delay is 20 FOD cycles + 8ns.
  */
 static u32 idtcm_get_dco_delay(struct idtcm_channel *channel)
 {
@@ -2196,7 +2196,7 @@ static u32 idtcm_get_dco_delay(struct idtcm_channel *channel)
 	fodFreq = (u32)div_u64(m, n);
 
 	if (fodFreq >= 500000000)
-		return (u32)div_u64(18 * (u64)NSEC_PER_SEC, fodFreq);
+		return (u32)div_u64(20 * (u64)NSEC_PER_SEC, fodFreq) + 8;
 
 	return 0;
 }
-- 
2.39.2