[PATCH i2c-next 2/2] i2c: aspeed: add slave inactive timeout support

[Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>]

In case of multi-master environment, if a peer master incorrectly handles
a bus in the middle of a transaction, I2C hardware hangs in slave state
and it can't escape from the slave state, so this commit adds slave
inactive timeout support to recover the bus in the case.

Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Tao Ren <taoren@fb.com>
---
 drivers/i2c/busses/i2c-aspeed.c | 83 ++++++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index a7be6f24450b..d43687cd2ddc 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -7,6 +7,7 @@
  *  Copyright 2017 Google, Inc.
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/completion.h>
 #include <linux/err.h>
@@ -43,6 +44,7 @@
 
 /* Device Register Definition */
 /* 0x00 : I2CD Function Control Register  */
+#define ASPEED_I2CD_BUS_AUTO_RECOVERY_EN		BIT(17)
 #define ASPEED_I2CD_MULTI_MASTER_DIS			BIT(15)
 #define ASPEED_I2CD_SDA_DRIVE_1T_EN			BIT(8)
 #define ASPEED_I2CD_M_SDA_DRIVE_1T_EN			BIT(7)
@@ -58,10 +60,14 @@
 #define ASPEED_I2CD_TIME_SCL_HIGH_MASK			GENMASK(19, 16)
 #define ASPEED_I2CD_TIME_SCL_LOW_SHIFT			12
 #define ASPEED_I2CD_TIME_SCL_LOW_MASK			GENMASK(15, 12)
+#define ASPEED_I2CD_TIME_TIMEOUT_BASE_DIVISOR_SHIFT	8
+#define ASPEED_I2CD_TIME_TIMEOUT_BASE_DIVISOR_MASK	GENMASK(9, 8)
 #define ASPEED_I2CD_TIME_BASE_DIVISOR_MASK		GENMASK(3, 0)
 #define ASPEED_I2CD_TIME_SCL_REG_MAX			GENMASK(3, 0)
+
 /* 0x08 : I2CD Clock and AC Timing Control Register #2 */
-#define ASPEED_NO_TIMEOUT_CTRL				0
+#define ASPEED_I2CD_TIMEOUT_CYCLES_SHIFT		0
+#define ASPEED_I2CD_TIMEOUT_CYCLES_MASK			GENMASK(4, 0)
 
 /* 0x0c : I2CD Interrupt Control Register &
  * 0x10 : I2CD Interrupt Status Register
@@ -69,6 +75,7 @@
  * These share bit definitions, so use the same values for the enable &
  * status bits.
  */
+#define ASPEED_I2CD_INTR_SLAVE_INACTIVE_TIMEOUT		BIT(15)
 #define ASPEED_I2CD_INTR_SDA_DL_TIMEOUT			BIT(14)
 #define ASPEED_I2CD_INTR_BUS_RECOVER_DONE		BIT(13)
 #define ASPEED_I2CD_INTR_SLAVE_MATCH			BIT(7)
@@ -84,8 +91,11 @@
 		 ASPEED_I2CD_INTR_SCL_TIMEOUT |				       \
 		 ASPEED_I2CD_INTR_ABNORMAL |				       \
 		 ASPEED_I2CD_INTR_ARBIT_LOSS)
+#define ASPEED_I2CD_INTR_SLAVE_ERRORS					       \
+		ASPEED_I2CD_INTR_SLAVE_INACTIVE_TIMEOUT
 #define ASPEED_I2CD_INTR_ALL						       \
-		(ASPEED_I2CD_INTR_SDA_DL_TIMEOUT |			       \
+		(ASPEED_I2CD_INTR_SLAVE_INACTIVE_TIMEOUT |		       \
+		 ASPEED_I2CD_INTR_SDA_DL_TIMEOUT |			       \
 		 ASPEED_I2CD_INTR_BUS_RECOVER_DONE |			       \
 		 ASPEED_I2CD_INTR_SCL_TIMEOUT |				       \
 		 ASPEED_I2CD_INTR_ABNORMAL |				       \
@@ -151,6 +161,7 @@ struct aspeed_i2c_bus {
 							   u32 divisor);
 	unsigned long			parent_clk_frequency;
 	u32				bus_frequency;
+	u32				hw_timeout_ms;
 	/* Transaction state. */
 	enum aspeed_i2c_master_state	master_state;
 	struct i2c_msg			*msgs;
@@ -240,6 +251,14 @@ static int aspeed_i2c_recover_bus(struct aspeed_i2c_bus *bus)
 }
 
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
+static int aspeed_i2c_check_slave_error(u32 irq_status)
+{
+	if (irq_status & ASPEED_I2CD_INTR_SLAVE_INACTIVE_TIMEOUT)
+		return -EIO;
+
+	return 0;
+}
+
 static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 {
 	u32 command, irq_handled = 0;
@@ -249,6 +268,14 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 	if (!slave)
 		return 0;
 
+	if (aspeed_i2c_check_slave_error(irq_status)) {
+		dev_dbg(bus->dev, "received slave error interrupt: 0x%08x\n",
+			irq_status);
+		irq_handled |= (irq_status & ASPEED_I2CD_INTR_SLAVE_ERRORS);
+		bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
+		return irq_handled;
+	}
+
 	command = readl(bus->base + ASPEED_I2C_CMD_REG);
 
 	/* Slave was requested, restart state machine. */
@@ -386,7 +413,7 @@ static void aspeed_i2c_next_msg_or_stop(struct aspeed_i2c_bus *bus)
 	}
 }
 
-static int aspeed_i2c_is_irq_error(u32 irq_status)
+static int aspeed_i2c_check_master_error(u32 irq_status)
 {
 	if (irq_status & ASPEED_I2CD_INTR_ARBIT_LOSS)
 		return -EAGAIN;
@@ -417,9 +444,9 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 	 * should clear the command queue effectively taking us back to the
 	 * INACTIVE state.
 	 */
-	ret = aspeed_i2c_is_irq_error(irq_status);
+	ret = aspeed_i2c_check_master_error(irq_status);
 	if (ret) {
-		dev_dbg(bus->dev, "received error interrupt: 0x%08x\n",
+		dev_dbg(bus->dev, "received master error interrupt: 0x%08x\n",
 			irq_status);
 		irq_handled |= (irq_status & ASPEED_I2CD_INTR_MASTER_ERRORS);
 		if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE) {
@@ -875,6 +902,7 @@ static u32 aspeed_i2c_25xx_get_clk_reg_val(struct device *dev, u32 divisor)
 /* precondition: bus.lock has been acquired. */
 static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus)
 {
+	u32 timeout_base_divisor, timeout_tick_us, timeout_cycles;
 	u32 divisor, clk_reg_val;
 
 	divisor = DIV_ROUND_UP(bus->parent_clk_frequency, bus->bus_frequency);
@@ -883,8 +911,46 @@ static int aspeed_i2c_init_clk(struct aspeed_i2c_bus *bus)
 			ASPEED_I2CD_TIME_THDSTA_MASK |
 			ASPEED_I2CD_TIME_TACST_MASK);
 	clk_reg_val |= bus->get_clk_reg_val(bus->dev, divisor);
+
+	if (bus->hw_timeout_ms) {
+		u8 div_max = ASPEED_I2CD_TIME_TIMEOUT_BASE_DIVISOR_MASK >>
+			     ASPEED_I2CD_TIME_TIMEOUT_BASE_DIVISOR_SHIFT;
+		u8 cycles_max = ASPEED_I2CD_TIMEOUT_CYCLES_MASK >>
+				ASPEED_I2CD_TIMEOUT_CYCLES_SHIFT;
+
+		timeout_base_divisor = 0;
+
+		do {
+			timeout_tick_us = 1000 * (16384 <<
+						  (timeout_base_divisor << 1)) /
+					  (bus->parent_clk_frequency / 1000);
+
+			if (timeout_base_divisor == div_max ||
+			    timeout_tick_us * ASPEED_I2CD_TIMEOUT_CYCLES_MASK >=
+			    bus->hw_timeout_ms * 1000)
+				break;
+		} while (timeout_base_divisor++ < div_max);
+
+		if (timeout_tick_us) {
+			timeout_cycles = DIV_ROUND_UP(bus->hw_timeout_ms * 1000,
+						      timeout_tick_us);
+			if (timeout_cycles == 0)
+				timeout_cycles = 1;
+			else if (timeout_cycles > cycles_max)
+				timeout_cycles = cycles_max;
+		} else {
+			timeout_cycles = 0;
+		}
+	} else {
+		timeout_base_divisor = 0;
+		timeout_cycles = 0;
+	}
+
+	clk_reg_val |= FIELD_PREP(ASPEED_I2CD_TIME_TIMEOUT_BASE_DIVISOR_MASK,
+				  timeout_base_divisor);
+
 	writel(clk_reg_val, bus->base + ASPEED_I2C_AC_TIMING_REG1);
-	writel(ASPEED_NO_TIMEOUT_CTRL, bus->base + ASPEED_I2C_AC_TIMING_REG2);
+	writel(timeout_cycles, bus->base + ASPEED_I2C_AC_TIMING_REG2);
 
 	return 0;
 }
@@ -899,6 +965,11 @@ static int aspeed_i2c_init(struct aspeed_i2c_bus *bus,
 	/* Disable everything. */
 	writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
 
+	device_property_read_u32(&pdev->dev, "aspeed,hw-timeout-ms",
+				 &bus->hw_timeout_ms);
+	if (bus->hw_timeout_ms)
+		fun_ctrl_reg |= ASPEED_I2CD_BUS_AUTO_RECOVERY_EN;
+
 	ret = aspeed_i2c_init_clk(bus);
 	if (ret < 0)
 		return ret;
-- 
2.23.0