net: dsa: microchip: ksz8795: handle eee specif erratum

According to erratum described in DS80000687C[1]: "Module 2: Link drops with
some EEE link partners.", we need to "Disable the EEE next page
exchange in EEE Global Register 2"

1 - https://ww1.microchip.com/downloads/en/DeviceDoc/KSZ87xx-Errata-DS80000687C.pdfSigned-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20220316125529.1489045-1-o.rempel@pengutronix.deSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/microchip/ksz8.h

@@ -16,6 +16,7 @@ enum ksz_regs {
 	REG_IND_DATA_HI,
 	REG_IND_DATA_LO,
 	REG_IND_MIB_CHECK,
+	REG_IND_BYTE,
 	P_FORCE_CTRL,
 	P_LINK_STATUS,
 	P_LOCAL_CTRL,

drivers/net/dsa/microchip/ksz8795.c

@@ -33,6 +33,7 @@ static const u8 ksz8795_regs[] = {
 	[REG_IND_DATA_HI]		= 0x71,
 	[REG_IND_DATA_LO]		= 0x75,
 	[REG_IND_MIB_CHECK]		= 0x74,
+	[REG_IND_BYTE]			= 0xA0,
 	[P_FORCE_CTRL]			= 0x0C,
 	[P_LINK_STATUS]			= 0x0E,
 	[P_LOCAL_CTRL]			= 0x07,
@@ -222,6 +223,25 @@ static void ksz_port_cfg(struct ksz_device *dev, int port, int offset, u8 bits,
 			   bits, set ? bits : 0);
 }
 
+static int ksz8_ind_write8(struct ksz_device *dev, u8 table, u16 addr, u8 data)
+{
+	struct ksz8 *ksz8 = dev->priv;
+	const u8 *regs = ksz8->regs;
+	u16 ctrl_addr;
+	int ret = 0;
+
+	mutex_lock(&dev->alu_mutex);
+
+	ctrl_addr = IND_ACC_TABLE(table) | addr;
+	ret = ksz_write8(dev, regs[REG_IND_BYTE], data);
+	if (!ret)
+		ret = ksz_write16(dev, regs[REG_IND_CTRL_0], ctrl_addr);
+
+	mutex_unlock(&dev->alu_mutex);
+
+	return ret;
+}
+
 static int ksz8_reset_switch(struct ksz_device *dev)
 {
 	if (ksz_is_ksz88x3(dev)) {
@@ -1391,6 +1411,23 @@ static void ksz8_config_cpu_port(struct dsa_switch *ds)
 	}
 }
 
+static int ksz8_handle_global_errata(struct dsa_switch *ds)
+{
+	struct ksz_device *dev = ds->priv;
+	int ret = 0;
+
+	/* KSZ87xx Errata DS80000687C.
+	 * Module 2: Link drops with some EEE link partners.
+	 *   An issue with the EEE next page exchange between the
+	 *   KSZ879x/KSZ877x/KSZ876x and some EEE link partners may result in
+	 *   the link dropping.
+	 */
+	if (dev->ksz87xx_eee_link_erratum)
+		ret = ksz8_ind_write8(dev, TABLE_EEE, REG_IND_EEE_GLOB2_HI, 0);
+
+	return ret;
+}
+
 static int ksz8_setup(struct dsa_switch *ds)
 {
 	struct ksz_device *dev = ds->priv;
@@ -1458,7 +1495,7 @@ static int ksz8_setup(struct dsa_switch *ds)
 
 	ds->configure_vlan_while_not_filtering = false;
 
-	return 0;
+	return ksz8_handle_global_errata(ds);
 }
 
 static void ksz8_get_caps(struct dsa_switch *ds, int port,
@@ -1575,6 +1612,7 @@ struct ksz_chip_data {
 	int num_statics;
 	int cpu_ports;
 	int port_cnt;
+	bool ksz87xx_eee_link_erratum;
 };
 
 static const struct ksz_chip_data ksz8_switch_chips[] = {
@@ -1586,6 +1624,7 @@ static const struct ksz_chip_data ksz8_switch_chips[] = {
 		.num_statics = 8,
 		.cpu_ports = 0x10,	/* can be configured as cpu port */
 		.port_cnt = 5,		/* total cpu and user ports */
+		.ksz87xx_eee_link_erratum = true,
 	},
 	{
 		/*
@@ -1609,6 +1648,7 @@ static const struct ksz_chip_data ksz8_switch_chips[] = {
 		.num_statics = 8,
 		.cpu_ports = 0x10,	/* can be configured as cpu port */
 		.port_cnt = 4,		/* total cpu and user ports */
+		.ksz87xx_eee_link_erratum = true,
 	},
 	{
 		.chip_id = 0x8765,
@@ -1618,6 +1658,7 @@ static const struct ksz_chip_data ksz8_switch_chips[] = {
 		.num_statics = 8,
 		.cpu_ports = 0x10,	/* can be configured as cpu port */
 		.port_cnt = 5,		/* total cpu and user ports */
+		.ksz87xx_eee_link_erratum = true,
 	},
 	{
 		.chip_id = 0x8830,
@@ -1652,6 +1693,8 @@ static int ksz8_switch_init(struct ksz_device *dev)
 			dev->host_mask = chip->cpu_ports;
 			dev->port_mask = (BIT(dev->phy_port_cnt) - 1) |
 					 chip->cpu_ports;
+			dev->ksz87xx_eee_link_erratum =
+				chip->ksz87xx_eee_link_erratum;
 			break;
 		}
 	}

drivers/net/dsa/microchip/ksz8795_reg.h

@@ -812,6 +812,10 @@
 
 #define IND_ACC_TABLE(table)		((table) << 8)
 
+/* */
+#define REG_IND_EEE_GLOB2_LO		0x34
+#define REG_IND_EEE_GLOB2_HI		0x35
+
 /* Driver set switch broadcast storm protection at 10% rate. */
 #define BROADCAST_STORM_PROT_RATE	10
 

drivers/net/dsa/microchip/ksz_common.h

@@ -77,6 +77,7 @@ struct ksz_device {
 	phy_interface_t compat_interface;
 	u32 regs_size;
 	bool phy_errata_9477;
+	bool ksz87xx_eee_link_erratum;
 	bool synclko_125;
 	bool synclko_disable;