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.pdf

Signed-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.de
Signed-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;