netdev - [PATCH net] net: dsa: microchip: disable EEE for KSZ8567/KSZ9567/KSZ9896/KSZ9897.

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Message-ID: <20240807205209.21464-1-foss@martin-whitaker.me.uk>
Date: Wed,  7 Aug 2024 21:52:09 +0100
From: Martin Whitaker <foss@...tin-whitaker.me.uk>
To: netdev@...r.kernel.org
Cc: UNGLinuxDriver@...rochip.com,
	Woojung.Huh@...rochip.com,
	o.rempel@...gutronix.de,
	lukma@...x.de,
	Arun.Ramadoss@...rochip.com,
	kuba@...nel.org,
	Martin Whitaker <foss@...tin-whitaker.me.uk>
Subject: [PATCH net] net: dsa: microchip: disable EEE for KSZ8567/KSZ9567/KSZ9896/KSZ9897.

As noted in the device errata [1-8], EEE support is not fully operational
in the KSZ8567, KSZ9477, KSZ9567, KSZ9896, and KSZ9897 devices, causing
link drops when connected to another device that supports EEE. The patch
series "net: add EEE support for KSZ9477 switch family" merged in commit
9b0bf4f77162 caused EEE support to be enabled in these devices. A fix for
this regression for the KSZ9477 alone was merged in commit 08c6d8bae48c2.
This patch extends this fix to the other affected devices.

[1] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ8567R-Errata-DS80000752.pdf
[2] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ8567S-Errata-DS80000753.pdf
[3] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9477S-Errata-DS80000754.pdf
[4] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9567R-Errata-DS80000755.pdf
[5] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9567S-Errata-DS80000756.pdf
[6] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9896C-Errata-DS80000757.pdf
[7] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9897R-Errata-DS80000758.pdf
[8] https://ww1.microchip.com/downloads/aemDocuments/documents/UNG/ProductDocuments/Errata/KSZ9897S-Errata-DS80000759.pdf

Fixes: 69d3b36ca045 ("net: dsa: microchip: enable EEE support") # for KSZ8567/KSZ9567/KSZ9896/KSZ9897
Link: https://lore.kernel.org/netdev/137ce1ee-0b68-4c96-a717-c8164b514eec@martin-whitaker.me.uk/
Signed-off-by: Martin Whitaker <foss@...tin-whitaker.me.uk>
---
 drivers/net/dsa/microchip/ksz_common.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index b074b4bb0629..cebc6eaa932b 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -2578,7 +2578,11 @@ static u32 ksz_get_phy_flags(struct dsa_switch *ds, int port)
 		if (!port)
 			return MICREL_KSZ8_P1_ERRATA;
 		break;
+	case KSZ8567_CHIP_ID:
 	case KSZ9477_CHIP_ID:
+	case KSZ9567_CHIP_ID:
+	case KSZ9896_CHIP_ID:
+	case KSZ9897_CHIP_ID:
 		/* KSZ9477 Errata DS80000754C
 		 *
 		 * Module 4: Energy Efficient Ethernet (EEE) feature select must
@@ -2588,6 +2592,13 @@ static u32 ksz_get_phy_flags(struct dsa_switch *ds, int port)
 		 *   controls. If not disabled, the PHY ports can auto-negotiate
 		 *   to enable EEE, and this feature can cause link drops when
 		 *   linked to another device supporting EEE.
+		 *
+		 * The same item appears in the errata for the KSZ9567, KSZ9896,
+		 * and KSZ9897.
+		 *
+		 * A similar item appears in the errata for the KSZ8567, but
+		 * provides an alternative workaround. For now, use the simple
+		 * workaround of disabling the EEE feature for this device too.
 		 */
 		return MICREL_NO_EEE;
 	}
--
2.41.1