netdev - [PATCH v4 2/2] e1000e: ignore uninitialized checksum word on tgp

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Message-ID: <28347e4f-c6a7-4194-8a80-34508891c8ec@jacekk.info>
Date: Mon, 30 Jun 2025 10:35:00 +0200
From: Jacek Kowalski <jacek@...ekk.info>
To: Tony Nguyen <anthony.l.nguyen@...el.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Simon Horman <horms@...nel.org>, Vlad URSU <vlad@...u.me>
Cc: intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org
Subject: [PATCH v4 2/2] e1000e: ignore uninitialized checksum word on tgp

As described by Vitaly Lifshits:

> Starting from Tiger Lake, LAN NVM is locked for writes by SW, so the
> driver cannot perform checksum validation and correction. This means
> that all NVM images must leave the factory with correct checksum and
> checksum valid bit set.

Unfortunately some systems have left the factory with an uninitialized
value of 0xFFFF at register address 0x3F (checksum word location).
So on Tiger Lake platform we ignore the computed checksum when such
condition is encountered.

Signed-off-by: Jacek Kowalski <Jacek@...ekk.info>
Tested-by: Vlad URSU <vlad@...u.me>
Fixes: 4051f68318ca9 ("e1000e: Do not take care about recovery NVM checksum")
Cc: stable@...r.kernel.org
---
 drivers/net/ethernet/intel/e1000e/defines.h | 3 +++
 drivers/net/ethernet/intel/e1000e/nvm.c     | 6 ++++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/intel/e1000e/defines.h b/drivers/net/ethernet/intel/e1000e/defines.h
index 8294a7c4f122..ba331899d186 100644
--- a/drivers/net/ethernet/intel/e1000e/defines.h
+++ b/drivers/net/ethernet/intel/e1000e/defines.h
@@ -638,6 +638,9 @@
 /* For checksumming, the sum of all words in the NVM should equal 0xBABA. */
 #define NVM_SUM                    0xBABA

+/* Uninitialized ("empty") checksum word value */
+#define NVM_CHECKSUM_UNINITIALIZED 0xFFFF
+
 /* PBA (printed board assembly) number words */
 #define NVM_PBA_OFFSET_0           8
 #define NVM_PBA_OFFSET_1           9
diff --git a/drivers/net/ethernet/intel/e1000e/nvm.c b/drivers/net/ethernet/intel/e1000e/nvm.c
index e609f4df86f4..16369e6d245a 100644
--- a/drivers/net/ethernet/intel/e1000e/nvm.c
+++ b/drivers/net/ethernet/intel/e1000e/nvm.c
@@ -558,6 +558,12 @@ s32 e1000e_validate_nvm_checksum_generic(struct e1000_hw *hw)
 		checksum += nvm_data;
 	}

+	if (hw->mac.type == e1000_pch_tgp &&
+	    nvm_data == NVM_CHECKSUM_UNINITIALIZED) {
+		e_dbg("Uninitialized NVM Checksum on TGP platform - ignoring\n");
+		return 0;
+	}
+
 	if (checksum != (u16)NVM_SUM) {
 		e_dbg("NVM Checksum Invalid\n");
 		return -E1000_ERR_NVM;
-- 
2.47.2