net: ti: cpsw-mdio: Add workaround for errata i2329

In certain TI SoCs, on the CPSW and ICSS peripherals, there is
a possibility that the MDIO interface returns corrupt data on
MDIO reads or writes incorrect data on MDIO writes. There is also
a possibility for the MDIO interface to become unavailable until
the next peripheral reset.

The workaround is to configure the MDIO in manual mode and disable the
MDIO state machine and emulate the MDIO protocol by reading and writing
appropriate fields in MDIO_MANUAL_IF_REG register of the MDIO controller
to manipulate the MDIO clock and data pins.

More details about the errata i2329 and the workaround is available in:
https://www.ti.com/lit/er/sprz487a/sprz487a.pdf

Add implementation to disable MDIO state machine, configure MDIO in manual
mode and provide software MDIO read and writes via MDIO bitbanging. Allow
the MDIO to be initialized based on the need for manual mode.

Signed-off-by: Ravi Gunasekaran <r-gunasekaran@ti.com>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>

5 files changed, 258 insertions, 8 deletions

diff --git a/drivers/net/ti/am65-cpsw-nuss.c b/drivers/net/ti/am65-cpsw-nuss.c
index b79e06290a2..3d0a329aa1a 100644
--- a/drivers/net/ti/am65-cpsw-nuss.c
+++ b/drivers/net/ti/am65-cpsw-nuss.c
@@ -552,7 +552,8 @@ static int am65_cpsw_mdio_init(struct udevice *dev)
 	cpsw_common->bus = cpsw_mdio_init(dev->name,
 					  cpsw_common->mdio_base,
 					  cpsw_common->bus_freq,
-					  clk_get_rate(&cpsw_common->fclk));
+					  clk_get_rate(&cpsw_common->fclk),
+					  false);
 	if (!cpsw_common->bus)
 		return -EFAULT;
 
diff --git a/drivers/net/ti/cpsw.c b/drivers/net/ti/cpsw.c
index 8988c21e667..41cba7930d1 100644
--- a/drivers/net/ti/cpsw.c
+++ b/drivers/net/ti/cpsw.c
@@ -922,7 +922,8 @@ int _cpsw_register(struct cpsw_priv *priv)
 		idx = idx + 1;
 	}
 
-	priv->bus = cpsw_mdio_init(priv->dev->name, data->mdio_base, 0, 0);
+	priv->bus = cpsw_mdio_init(priv->dev->name, data->mdio_base, 0, 0,
+				   false);
 	if (!priv->bus)
 		return -EFAULT;
 
diff --git a/drivers/net/ti/cpsw_mdio.c b/drivers/net/ti/cpsw_mdio.c
index f4cb86d10a7..a5ba73b7398 100644
--- a/drivers/net/ti/cpsw_mdio.c
+++ b/drivers/net/ti/cpsw_mdio.c
@@ -23,6 +23,11 @@ struct cpsw_mdio_regs {
 #define CONTROL_FAULT_ENABLE	BIT(18)
 #define CONTROL_DIV_MASK	GENMASK(15, 0)
 
+#define MDIO_MAN_MDCLK_O        BIT(2)
+#define MDIO_MAN_OE             BIT(1)
+#define MDIO_MAN_PIN            BIT(0)
+#define MDIO_MANUALMODE         BIT(31)
+
 	u32	alive;
 	u32	link;
 	u32	linkintraw;
@@ -32,7 +37,9 @@ struct cpsw_mdio_regs {
 	u32	userintmasked;
 	u32	userintmaskset;
 	u32	userintmaskclr;
-	u32	__reserved_1[20];
+	u32	manualif;
+	u32	poll;
+	u32	__reserved_1[18];
 
 	struct {
 		u32		access;
@@ -51,6 +58,13 @@ struct cpsw_mdio_regs {
 #define PHY_REG_MASK		0x1f
 #define PHY_ID_MASK		0x1f
 
+#define MDIO_BITRANGE           0x8000
+#define C22_READ_PATTERN        0x6
+#define C22_WRITE_PATTERN       0x5
+#define C22_BITRANGE            0x8
+#define PHY_BITRANGE            0x10
+#define PHY_DATA_BITRANGE       0x8000
+
 /*
  * This timeout definition is a worst-case ultra defensive measure against
  * unexpected controller lock ups.  Ideally, we should never ever hit this
@@ -58,12 +72,239 @@ struct cpsw_mdio_regs {
  */
 #define CPSW_MDIO_TIMEOUT            100 /* msecs */
 
+enum cpsw_mdio_manual {
+	MDIO_PIN = 0,
+	MDIO_OE,
+	MDIO_MDCLK,
+};
+
 struct cpsw_mdio {
 	struct cpsw_mdio_regs *regs;
 	struct mii_dev *bus;
 	int div;
 };
 
+static void cpsw_mdio_disable(struct cpsw_mdio *mdio)
+{
+	u32 reg;
+	/* Disable MDIO state machine */
+	reg = readl(&mdio->regs->control);
+	reg &= ~CONTROL_ENABLE;
+
+	writel(reg, &mdio->regs->control);
+}
+
+static void cpsw_mdio_enable_manual_mode(struct cpsw_mdio *mdio)
+{
+	u32 reg;
+
+	/* set manual mode */
+	reg = readl(&mdio->regs->poll);
+	reg |= MDIO_MANUALMODE;
+
+	writel(reg, &mdio->regs->poll);
+}
+
+static void cpsw_mdio_sw_set_bit(struct cpsw_mdio *mdio,
+				 enum cpsw_mdio_manual bit)
+{
+	u32 reg;
+
+	reg = readl(&mdio->regs->manualif);
+
+	switch (bit) {
+	case MDIO_OE:
+		reg |= MDIO_MAN_OE;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	case MDIO_PIN:
+		reg |= MDIO_MAN_PIN;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	case MDIO_MDCLK:
+		reg |= MDIO_MAN_MDCLK_O;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	default:
+		break;
+	};
+}
+
+static void cpsw_mdio_sw_clr_bit(struct cpsw_mdio *mdio,
+				 enum cpsw_mdio_manual bit)
+{
+	u32 reg;
+
+	reg = readl(&mdio->regs->manualif);
+
+	switch (bit) {
+	case MDIO_OE:
+		reg &= ~MDIO_MAN_OE;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	case MDIO_PIN:
+		reg &= ~MDIO_MAN_PIN;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	case MDIO_MDCLK:
+		reg = readl(&mdio->regs->manualif);
+		reg &= ~MDIO_MAN_MDCLK_O;
+		writel(reg, &mdio->regs->manualif);
+		break;
+	default:
+		break;
+	};
+}
+
+static int cpsw_mdio_test_man_bit(struct cpsw_mdio *mdio,
+				  enum cpsw_mdio_manual bit)
+{
+	u32 reg;
+
+	reg = readl(&mdio->regs->manualif);
+	return test_bit(bit, &reg);
+}
+
+static void cpsw_mdio_toggle_man_bit(struct cpsw_mdio *mdio,
+				     enum cpsw_mdio_manual bit)
+{
+	cpsw_mdio_sw_clr_bit(mdio, bit);
+	cpsw_mdio_sw_set_bit(mdio, bit);
+}
+
+static void cpsw_mdio_man_send_pattern(struct cpsw_mdio *mdio,
+				       u32 bitrange, u32 val)
+{
+	u32 i;
+
+	for (i = bitrange; i; i = i >> 1) {
+		if (i & val)
+			cpsw_mdio_sw_set_bit(mdio, MDIO_PIN);
+		else
+			cpsw_mdio_sw_clr_bit(mdio, MDIO_PIN);
+
+		cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+	}
+}
+
+static void cpsw_mdio_sw_preamble(struct cpsw_mdio *mdio)
+{
+	u32 i;
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_OE);
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_set_bit(mdio, MDIO_MDCLK);
+
+	for (i = 0; i < 32; i++) {
+		cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+		cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+		cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+		cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+	}
+}
+
+static int cpsw_mdio_sw_read(struct mii_dev *bus, int phy_id,
+			     int dev_addr, int phy_reg)
+{
+	struct cpsw_mdio *mdio = bus->priv;
+	u32 reg, i;
+	u8 ack;
+
+	if (phy_reg & ~PHY_REG_MASK || phy_id & ~PHY_ID_MASK)
+		return -EINVAL;
+
+	cpsw_mdio_disable(mdio);
+	cpsw_mdio_enable_manual_mode(mdio);
+	cpsw_mdio_sw_preamble(mdio);
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_set_bit(mdio, MDIO_OE);
+
+	/* Issue clause 22 MII read function {0,1,1,0} */
+	cpsw_mdio_man_send_pattern(mdio, C22_BITRANGE, C22_READ_PATTERN);
+
+	/* Send the device number MSB first */
+	cpsw_mdio_man_send_pattern(mdio, PHY_BITRANGE, phy_id);
+
+	/* Send the register number MSB first */
+	cpsw_mdio_man_send_pattern(mdio, PHY_BITRANGE, phy_reg);
+
+	/* Send turn around cycles */
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_OE);
+
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+	ack = cpsw_mdio_test_man_bit(mdio, MDIO_PIN);
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+	reg = 0;
+	if (ack == 0) {
+		for (i = MDIO_BITRANGE; i; i = i >> 1) {
+			if (cpsw_mdio_test_man_bit(mdio, MDIO_PIN))
+				reg |= i;
+
+			cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+		}
+	} else {
+		for (i = MDIO_BITRANGE; i; i = i >> 1)
+			cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+		reg = 0xFFFF;
+	}
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_set_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_set_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+	return reg;
+}
+
+static int cpsw_mdio_sw_write(struct mii_dev *bus, int phy_id,
+			      int dev_addr, int phy_reg, u16 phy_data)
+{
+	struct cpsw_mdio *mdio = bus->priv;
+
+	if ((phy_reg & ~PHY_REG_MASK) || (phy_id & ~PHY_ID_MASK))
+		return -EINVAL;
+
+	cpsw_mdio_disable(mdio);
+	cpsw_mdio_enable_manual_mode(mdio);
+	cpsw_mdio_sw_preamble(mdio);
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_set_bit(mdio, MDIO_OE);
+
+	/* Issue clause 22 MII write function {0,1,0,1} */
+	cpsw_mdio_man_send_pattern(mdio, C22_BITRANGE, C22_WRITE_PATTERN);
+
+	/* Send the device number MSB first */
+	cpsw_mdio_man_send_pattern(mdio, PHY_BITRANGE, phy_id);
+
+	/* Send the register number MSB first */
+	cpsw_mdio_man_send_pattern(mdio, PHY_BITRANGE, phy_reg);
+
+	/* set turn-around cycles */
+	cpsw_mdio_sw_set_bit(mdio, MDIO_PIN);
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_PIN);
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+	/* Send Register data MSB first */
+	cpsw_mdio_man_send_pattern(mdio, PHY_DATA_BITRANGE, phy_data);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_OE);
+
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_sw_clr_bit(mdio, MDIO_MDCLK);
+	cpsw_mdio_toggle_man_bit(mdio, MDIO_MDCLK);
+
+	return 0;
+}
+
 /* wait until hardware is ready for another user access */
 static int cpsw_mdio_wait_for_user_access(struct cpsw_mdio *mdio)
 {
@@ -130,7 +371,7 @@ u32 cpsw_mdio_get_alive(struct mii_dev *bus)
 }
 
 struct mii_dev *cpsw_mdio_init(const char *name, phys_addr_t mdio_base,
-			       u32 bus_freq, int fck_freq)
+			       u32 bus_freq, int fck_freq, bool manual_mode)
 {
 	struct cpsw_mdio *cpsw_mdio;
 	int ret;
@@ -172,8 +413,14 @@ struct mii_dev *cpsw_mdio_init(const char *name, phys_addr_t mdio_base,
 	 */
 	mdelay(1);
 
-	cpsw_mdio->bus->read = cpsw_mdio_read;
-	cpsw_mdio->bus->write = cpsw_mdio_write;
+	if (manual_mode) {
+		cpsw_mdio->bus->read = cpsw_mdio_sw_read;
+		cpsw_mdio->bus->write = cpsw_mdio_sw_write;
+	} else {
+		cpsw_mdio->bus->read = cpsw_mdio_read;
+		cpsw_mdio->bus->write = cpsw_mdio_write;
+	}
+
 	cpsw_mdio->bus->priv = cpsw_mdio;
 	snprintf(cpsw_mdio->bus->name, sizeof(cpsw_mdio->bus->name), name);
 
diff --git a/drivers/net/ti/cpsw_mdio.h b/drivers/net/ti/cpsw_mdio.h
index dbf4a2dcacb..9b98763656f 100644
--- a/drivers/net/ti/cpsw_mdio.h
+++ b/drivers/net/ti/cpsw_mdio.h
@@ -11,7 +11,7 @@
 struct cpsw_mdio;
 
 struct mii_dev *cpsw_mdio_init(const char *name, phys_addr_t mdio_base,
-			       u32 bus_freq, int fck_freq);
+			       u32 bus_freq, int fck_freq, bool manual_mode);
 void cpsw_mdio_free(struct mii_dev *bus);
 u32 cpsw_mdio_get_alive(struct mii_dev *bus);
 
diff --git a/drivers/net/ti/keystone_net.c b/drivers/net/ti/keystone_net.c
index fbec69f5717..1bdbd599d7b 100644
--- a/drivers/net/ti/keystone_net.c
+++ b/drivers/net/ti/keystone_net.c
@@ -571,7 +571,8 @@ static int ks2_eth_probe(struct udevice *dev)
 		mdio_bus = cpsw_mdio_init("ethernet-mdio",
 					  priv->mdio_base,
 					  EMAC_MDIO_CLOCK_FREQ,
-					  EMAC_MDIO_BUS_FREQ);
+					  EMAC_MDIO_BUS_FREQ,
+					  false);
 		if (!mdio_bus) {
 			pr_err("MDIO alloc failed\n");
 			return -ENOMEM;