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
9b0bf4f caused EEE support to be enabled in these devices. A fix for
this regression for the KSZ9477 alone was merged in commit 08c6d8b.
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: 69d3b36 ("net: dsa: microchip: enable EEE support") # for KSZ8567/KSZ9567/KSZ9896/KSZ9897
Link: https://lore.kernel.org/netdev/[email protected]/
Signed-off-by: Martin Whitaker <[email protected]>
Acked-by: Arun Ramadoss <[email protected]>
Reviewed-by: Oleksij Rempel <[email protected]>
Reviewed-by: Lukasz Majewski <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: martinwhitaker

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;
 	}