linux-kernel - [PATCH] i40e: fix the wrong PTP frequency calculation

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Date:   Tue, 27 Jun 2023 10:26:58 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, richardcochran@...il.com,
        jacob.e.keller@...el.com
Cc:     intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yajun Deng <yajun.deng@...ux.dev>,
        stable@...r.kernel.org
Subject: [PATCH] i40e: fix the wrong PTP frequency calculation

The new adjustment should be based on the base frequency, not the
I40E_PTP_40GB_INCVAL in i40e_ptp_adjfine().

This issue was introduced in commit 3626a690b717 ("i40e: use
mul_u64_u64_div_u64 for PTP frequency calculation"), and was fixed in
commit 1060707e3809 ("ptp: introduce helpers to adjust by scaled
parts per million"). However the latter is a new feature and hasn't been
backported to the stable releases.

This issue affects both v6.0 and v6.1 versions, and the v6.1 version is
an LTS version.

Fixes: 3626a690b717 ("i40e: use mul_u64_u64_div_u64 for PTP frequency calculation")
Cc: <stable@...r.kernel.org> # 6.1
Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
---
 drivers/net/ethernet/intel/i40e/i40e_ptp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/i40e/i40e_ptp.c b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
index ffea0c9c82f1..97a9efe7b713 100644
--- a/drivers/net/ethernet/intel/i40e/i40e_ptp.c
+++ b/drivers/net/ethernet/intel/i40e/i40e_ptp.c
@@ -361,9 +361,9 @@ static int i40e_ptp_adjfine(struct ptp_clock_info *ptp, long scaled_ppm)
 				   1000000ULL << 16);
 
 	if (neg_adj)
-		adj = I40E_PTP_40GB_INCVAL - diff;
+		adj = freq - diff;
 	else
-		adj = I40E_PTP_40GB_INCVAL + diff;
+		adj = freq + diff;
 
 	wr32(hw, I40E_PRTTSYN_INC_L, adj & 0xFFFFFFFF);
 	wr32(hw, I40E_PRTTSYN_INC_H, adj >> 32);
-- 
2.25.1