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From:   Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
To:     Brendan Higgins <brendanhiggins@google.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>, linux-i2c@vger.kernel.org,
        openbmc@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org,
        linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org
Cc:     James Feist <james.feist@linux.intel.com>,
        Vernon Mauery <vernon.mauery@linux.intel.com>,
        Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Subject: [PATCH] i2c: aspeed: Improve driver to support multi-master use cases stably
Date:   Tue, 26 Jun 2018 09:58:12 -0700
Message-Id: <20180626165812.4141-1-jae.hyun.yoo@linux.intel.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

BMC firmware should support some multi-master use cases such as multi-node,
IPMB, BMC-ME link and so on but the current ASPEED I2C driver is a bit
unstable for the multi-master use case. So this patch improves ASPEED I2C
driver to support the multi-master use case stably.

Changes:
* Added XFER_MODE status register checking logic into
  aspeed_i2c_master_xfer to improve the current bus busy checking logic.
* Changed the order of enum aspeed_i2c_master_state and
  enum aspeed_i2c_slave_state defines to make their initial values set to
  ASPEED_I2C_MASTER_INACTIVE and ASPEED_I2C_SLAVE_STOP respectively.
  In case of multi-master use with previous code, if a slave data comes
  ahead of the first master xfer, master_state starts from an invalid
  state. This change fixed the issue.
* Adjusted spin_lock scope to make it wrap the whole irq handler using
  a single lock and unlock pair covers both master and slave handlers.
* Added irq_status variable as a member of the struct aspeed_i2c_bus to
  collect handled interrupt bits throughout the master and the slave irq
  handlers.
* Added control logic to put an order on calling the master and the slave
  irq handlers based on their current states.

Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
---
 drivers/i2c/busses/i2c-aspeed.c | 200 +++++++++++++++++++-------------
 1 file changed, 118 insertions(+), 82 deletions(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 60e4d0e939a3..ac3e17d9a365 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -4,6 +4,7 @@
  *  Copyright (C) 2012-2017 ASPEED Technology Inc.
  *  Copyright 2017 IBM Corporation
  *  Copyright 2017 Google, Inc.
+ *  Copyright (c) 2018 Intel Corporation
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License version 2 as
@@ -12,6 +13,7 @@
 
 #include <linux/clk.h>
 #include <linux/completion.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/i2c.h>
@@ -82,6 +84,11 @@
 #define ASPEED_I2CD_INTR_RX_DONE			BIT(2)
 #define ASPEED_I2CD_INTR_TX_NAK				BIT(1)
 #define ASPEED_I2CD_INTR_TX_ACK				BIT(0)
+#define ASPEED_I2CD_INTR_ERRORS						       \
+		(ASPEED_I2CD_INTR_SDA_DL_TIMEOUT |			       \
+		 ASPEED_I2CD_INTR_SCL_TIMEOUT |				       \
+		 ASPEED_I2CD_INTR_ABNORMAL |				       \
+		 ASPEED_I2CD_INTR_ARBIT_LOSS)
 #define ASPEED_I2CD_INTR_ALL						       \
 		(ASPEED_I2CD_INTR_SDA_DL_TIMEOUT |			       \
 		 ASPEED_I2CD_INTR_BUS_RECOVER_DONE |			       \
@@ -94,6 +101,7 @@
 		 ASPEED_I2CD_INTR_TX_ACK)
 
 /* 0x14 : I2CD Command/Status Register   */
+#define ASPEED_I2CD_XFER_MODE_STS_MASK			GENMASK(22, 19)
 #define ASPEED_I2CD_SCL_LINE_STS			BIT(18)
 #define ASPEED_I2CD_SDA_LINE_STS			BIT(17)
 #define ASPEED_I2CD_BUS_BUSY_STS			BIT(16)
@@ -110,23 +118,27 @@
 /* 0x18 : I2CD Slave Device Address Register   */
 #define ASPEED_I2CD_DEV_ADDR_MASK			GENMASK(6, 0)
 
+/* Timeout for bus busy checking */
+#define BUS_BUSY_CHECK_TIMEOUT				250000 /* 250ms */
+#define BUS_BUSY_CHECK_INTERVAL				10000  /* 10ms */
+
 enum aspeed_i2c_master_state {
+	ASPEED_I2C_MASTER_INACTIVE,
 	ASPEED_I2C_MASTER_START,
 	ASPEED_I2C_MASTER_TX_FIRST,
 	ASPEED_I2C_MASTER_TX,
 	ASPEED_I2C_MASTER_RX_FIRST,
 	ASPEED_I2C_MASTER_RX,
 	ASPEED_I2C_MASTER_STOP,
-	ASPEED_I2C_MASTER_INACTIVE,
 };
 
 enum aspeed_i2c_slave_state {
+	ASPEED_I2C_SLAVE_STOP,
 	ASPEED_I2C_SLAVE_START,
 	ASPEED_I2C_SLAVE_READ_REQUESTED,
 	ASPEED_I2C_SLAVE_READ_PROCESSED,
 	ASPEED_I2C_SLAVE_WRITE_REQUESTED,
 	ASPEED_I2C_SLAVE_WRITE_RECEIVED,
-	ASPEED_I2C_SLAVE_STOP,
 };
 
 struct aspeed_i2c_bus {
@@ -150,6 +162,7 @@ struct aspeed_i2c_bus {
 	int				cmd_err;
 	/* Protected only by i2c_lock_bus */
 	int				master_xfer_result;
+	u32				irq_status;
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 	struct i2c_client		*slave;
 	enum aspeed_i2c_slave_state	slave_state;
@@ -229,37 +242,30 @@ static int aspeed_i2c_recover_bus(struct aspeed_i2c_bus *bus)
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 static bool aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus)
 {
-	u32 command, irq_status, status_ack = 0;
+	u32 command, status_ack = 0;
 	struct i2c_client *slave = bus->slave;
-	bool irq_handled = true;
 	u8 value;
 
-	spin_lock(&bus->lock);
-	if (!slave) {
-		irq_handled = false;
-		goto out;
-	}
+	if (!slave)
+		return false;
 
 	command = readl(bus->base + ASPEED_I2C_CMD_REG);
-	irq_status = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
 
 	/* Slave was requested, restart state machine. */
-	if (irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH) {
+	if (bus->irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH) {
 		status_ack |= ASPEED_I2CD_INTR_SLAVE_MATCH;
 		bus->slave_state = ASPEED_I2C_SLAVE_START;
 	}
 
 	/* Slave is not currently active, irq was for someone else. */
-	if (bus->slave_state == ASPEED_I2C_SLAVE_STOP) {
-		irq_handled = false;
-		goto out;
-	}
+	if (bus->slave_state == ASPEED_I2C_SLAVE_STOP)
+		return false;
 
 	dev_dbg(bus->dev, "slave irq status 0x%08x, cmd 0x%08x\n",
-		irq_status, command);
+		bus->irq_status, command);
 
 	/* Slave was sent something. */
-	if (irq_status & ASPEED_I2CD_INTR_RX_DONE) {
+	if (bus->irq_status & ASPEED_I2CD_INTR_RX_DONE) {
 		value = readl(bus->base + ASPEED_I2C_BYTE_BUF_REG) >> 8;
 		/* Handle address frame. */
 		if (bus->slave_state == ASPEED_I2C_SLAVE_START) {
@@ -274,28 +280,29 @@ static bool aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus)
 	}
 
 	/* Slave was asked to stop. */
-	if (irq_status & ASPEED_I2CD_INTR_NORMAL_STOP) {
+	if (bus->irq_status & ASPEED_I2CD_INTR_NORMAL_STOP) {
 		status_ack |= ASPEED_I2CD_INTR_NORMAL_STOP;
 		bus->slave_state = ASPEED_I2C_SLAVE_STOP;
 	}
-	if (irq_status & ASPEED_I2CD_INTR_TX_NAK) {
+	if (bus->irq_status & ASPEED_I2CD_INTR_TX_NAK) {
 		status_ack |= ASPEED_I2CD_INTR_TX_NAK;
 		bus->slave_state = ASPEED_I2C_SLAVE_STOP;
 	}
+	if (bus->irq_status & ASPEED_I2CD_INTR_TX_ACK) {
+		status_ack |= ASPEED_I2CD_INTR_TX_ACK;
+	}
 
 	switch (bus->slave_state) {
 	case ASPEED_I2C_SLAVE_READ_REQUESTED:
-		if (irq_status & ASPEED_I2CD_INTR_TX_ACK)
+		if (bus->irq_status & ASPEED_I2CD_INTR_TX_ACK)
 			dev_err(bus->dev, "Unexpected ACK on read request.\n");
 		bus->slave_state = ASPEED_I2C_SLAVE_READ_PROCESSED;
-
 		i2c_slave_event(slave, I2C_SLAVE_READ_REQUESTED, &value);
 		writel(value, bus->base + ASPEED_I2C_BYTE_BUF_REG);
 		writel(ASPEED_I2CD_S_TX_CMD, bus->base + ASPEED_I2C_CMD_REG);
 		break;
 	case ASPEED_I2C_SLAVE_READ_PROCESSED:
-		status_ack |= ASPEED_I2CD_INTR_TX_ACK;
-		if (!(irq_status & ASPEED_I2CD_INTR_TX_ACK))
+		if (!(bus->irq_status & ASPEED_I2CD_INTR_TX_ACK))
 			dev_err(bus->dev,
 				"Expected ACK after processed read.\n");
 		i2c_slave_event(slave, I2C_SLAVE_READ_PROCESSED, &value);
@@ -318,15 +325,8 @@ static bool aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus)
 		break;
 	}
 
-	if (status_ack != irq_status)
-		dev_err(bus->dev,
-			"irq handled != irq. expected %x, but was %x\n",
-			irq_status, status_ack);
-	writel(status_ack, bus->base + ASPEED_I2C_INTR_STS_REG);
-
-out:
-	spin_unlock(&bus->lock);
-	return irq_handled;
+	bus->irq_status ^= status_ack;
+	return !bus->irq_status;
 }
 #endif /* CONFIG_I2C_SLAVE */
 
@@ -384,20 +384,19 @@ static int aspeed_i2c_is_irq_error(u32 irq_status)
 
 static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 {
-	u32 irq_status, status_ack = 0, command = 0;
+	u32 status_ack = 0, command = 0;
 	struct i2c_msg *msg;
 	u8 recv_byte;
 	int ret;
 
-	spin_lock(&bus->lock);
-	irq_status = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
-	/* Ack all interrupt bits. */
-	writel(irq_status, bus->base + ASPEED_I2C_INTR_STS_REG);
-
-	if (irq_status & ASPEED_I2CD_INTR_BUS_RECOVER_DONE) {
+	if (bus->irq_status & ASPEED_I2CD_INTR_BUS_RECOVER_DONE) {
 		bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
 		status_ack |= ASPEED_I2CD_INTR_BUS_RECOVER_DONE;
 		goto out_complete;
+	} else {
+		/* Master is not currently active, irq was for someone else. */
+		if (bus->master_state == ASPEED_I2C_MASTER_INACTIVE)
+			goto out_no_complete;
 	}
 
 	/*
@@ -405,20 +404,23 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 	 * should clear the command queue effectively taking us back to the
 	 * INACTIVE state.
 	 */
-	ret = aspeed_i2c_is_irq_error(irq_status);
-	if (ret < 0) {
-		dev_dbg(bus->dev, "received error interrupt: 0x%08x",
-			irq_status);
+	ret = aspeed_i2c_is_irq_error(bus->irq_status);
+	if (ret) {
+		dev_dbg(bus->dev, "received error interrupt: 0x%08x\n",
+			bus->irq_status);
 		bus->cmd_err = ret;
 		bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
+		status_ack |= (bus->irq_status & ASPEED_I2CD_INTR_ERRORS);
 		goto out_complete;
 	}
 
 	/* We are in an invalid state; reset bus to a known state. */
 	if (!bus->msgs) {
-		dev_err(bus->dev, "bus in unknown state");
+		dev_err(bus->dev, "bus in unknown state irq_status: 0x%x\n",
+			bus->irq_status);
 		bus->cmd_err = -EIO;
-		if (bus->master_state != ASPEED_I2C_MASTER_STOP)
+		if (bus->master_state != ASPEED_I2C_MASTER_STOP &&
+		    bus->master_state != ASPEED_I2C_MASTER_INACTIVE)
 			aspeed_i2c_do_stop(bus);
 		goto out_no_complete;
 	}
@@ -430,7 +432,13 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 	 * then update the state and handle the new state below.
 	 */
 	if (bus->master_state == ASPEED_I2C_MASTER_START) {
-		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
+		if (unlikely(!(bus->irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
+			if (unlikely(!(bus->irq_status &
+				     ASPEED_I2CD_INTR_TX_NAK))) {
+				bus->cmd_err = -ENXIO;
+				bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
+				goto out_complete;
+			}
 			pr_devel("no slave present at %02x", msg->addr);
 			status_ack |= ASPEED_I2CD_INTR_TX_NAK;
 			bus->cmd_err = -ENXIO;
@@ -450,12 +458,13 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 
 	switch (bus->master_state) {
 	case ASPEED_I2C_MASTER_TX:
-		if (unlikely(irq_status & ASPEED_I2CD_INTR_TX_NAK)) {
-			dev_dbg(bus->dev, "slave NACKed TX");
+		if (unlikely(bus->irq_status & ASPEED_I2CD_INTR_TX_NAK)) {
+			dev_dbg(bus->dev, "slave NACKed TX\n");
 			status_ack |= ASPEED_I2CD_INTR_TX_NAK;
 			goto error_and_stop;
-		} else if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
-			dev_err(bus->dev, "slave failed to ACK TX");
+		} else if (unlikely(!(bus->irq_status &
+				      ASPEED_I2CD_INTR_TX_ACK))) {
+			dev_err(bus->dev, "slave failed to ACK TX\n");
 			goto error_and_stop;
 		}
 		status_ack |= ASPEED_I2CD_INTR_TX_ACK;
@@ -473,12 +482,12 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 		goto out_no_complete;
 	case ASPEED_I2C_MASTER_RX_FIRST:
 		/* RX may not have completed yet (only address cycle) */
-		if (!(irq_status & ASPEED_I2CD_INTR_RX_DONE))
+		if (!(bus->irq_status & ASPEED_I2CD_INTR_RX_DONE))
 			goto out_no_complete;
 		/* fallthrough intended */
 	case ASPEED_I2C_MASTER_RX:
-		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_RX_DONE))) {
-			dev_err(bus->dev, "master failed to RX");
+		if (unlikely(!(bus->irq_status & ASPEED_I2CD_INTR_RX_DONE))) {
+			dev_err(bus->dev, "master failed to RX\n");
 			goto error_and_stop;
 		}
 		status_ack |= ASPEED_I2CD_INTR_RX_DONE;
@@ -508,8 +517,11 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 		}
 		goto out_no_complete;
 	case ASPEED_I2C_MASTER_STOP:
-		if (unlikely(!(irq_status & ASPEED_I2CD_INTR_NORMAL_STOP))) {
-			dev_err(bus->dev, "master failed to STOP");
+		if (unlikely(!(bus->irq_status &
+			       ASPEED_I2CD_INTR_NORMAL_STOP))) {
+			dev_err(bus->dev,
+				"master failed to STOP irq_status:0x%x\n",
+				bus->irq_status);
 			bus->cmd_err = -EIO;
 			/* Do not STOP as we have already tried. */
 		} else {
@@ -520,8 +532,8 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 		goto out_complete;
 	case ASPEED_I2C_MASTER_INACTIVE:
 		dev_err(bus->dev,
-			"master received interrupt 0x%08x, but is inactive",
-			irq_status);
+			"master received interrupt 0x%08x, but is inactive\n",
+			bus->irq_status);
 		bus->cmd_err = -EIO;
 		/* Do not STOP as we should be inactive. */
 		goto out_complete;
@@ -543,26 +555,61 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
 		bus->master_xfer_result = bus->msgs_index + 1;
 	complete(&bus->cmd_complete);
 out_no_complete:
-	if (irq_status != status_ack)
-		dev_err(bus->dev,
-			"irq handled != irq. expected 0x%08x, but was 0x%08x\n",
-			irq_status, status_ack);
-	spin_unlock(&bus->lock);
-	return !!irq_status;
+	bus->irq_status ^= status_ack;
+	return !bus->irq_status;
 }
 
 static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
 {
 	struct aspeed_i2c_bus *bus = dev_id;
+	u32 irq_received;
+
+	spin_lock(&bus->lock);
+	irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
+	bus->irq_status = irq_received;
 
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
-	if (aspeed_i2c_slave_irq(bus)) {
-		dev_dbg(bus->dev, "irq handled by slave.\n");
-		return IRQ_HANDLED;
+	if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE) {
+		if (!aspeed_i2c_master_irq(bus))
+			aspeed_i2c_slave_irq(bus);
+	} else {
+		if (!aspeed_i2c_slave_irq(bus))
+			aspeed_i2c_master_irq(bus);
 	}
+#else
+	aspeed_i2c_master_irq(bus);
 #endif /* CONFIG_I2C_SLAVE */
 
-	return aspeed_i2c_master_irq(bus) ? IRQ_HANDLED : IRQ_NONE;
+	if (bus->irq_status)
+		dev_err(bus->dev,
+			"irq handled != irq. expected 0x%08x, but was 0x%08x\n",
+			irq_received, irq_received ^ bus->irq_status);
+
+	/* Ack all interrupt bits. */
+	writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
+	spin_unlock(&bus->lock);
+	return bus->irq_status ? IRQ_NONE : IRQ_HANDLED;
+}
+
+static int aspeed_i2c_check_bus_busy_timeout(struct aspeed_i2c_bus *bus)
+{
+	ktime_t timeout = ktime_add_us(ktime_get(), BUS_BUSY_CHECK_TIMEOUT);
+
+	might_sleep();
+
+	for (;;) {
+		if (!(readl(bus->base + ASPEED_I2C_CMD_REG) &
+		      (ASPEED_I2CD_BUS_BUSY_STS |
+		       ASPEED_I2CD_XFER_MODE_STS_MASK)))
+			return 0;
+		if (ktime_compare(ktime_get(), timeout) > 0)
+			break;
+		usleep_range((BUS_BUSY_CHECK_INTERVAL >> 2) + 1,
+			     BUS_BUSY_CHECK_INTERVAL);
+	}
+
+	dev_err(bus->dev, "timeout waiting for idle. attempting recovery\n");
+	return aspeed_i2c_recover_bus(bus);
 }
 
 static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
@@ -570,22 +617,11 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
 {
 	struct aspeed_i2c_bus *bus = i2c_get_adapdata(adap);
 	unsigned long time_left, flags;
-	int ret = 0;
-
-	spin_lock_irqsave(&bus->lock, flags);
-	bus->cmd_err = 0;
 
-	/* If bus is busy, attempt recovery. We assume a single master
-	 * environment.
-	 */
-	if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_BUS_BUSY_STS) {
-		spin_unlock_irqrestore(&bus->lock, flags);
-		ret = aspeed_i2c_recover_bus(bus);
-		if (ret)
-			return ret;
-		spin_lock_irqsave(&bus->lock, flags);
-	}
+	if (aspeed_i2c_check_bus_busy_timeout(bus))
+		return -EAGAIN;
 
+	spin_lock_irqsave(&bus->lock, flags);
 	bus->cmd_err = 0;
 	bus->msgs = msgs;
 	bus->msgs_index = 0;
@@ -851,7 +887,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
 	bus->rst = devm_reset_control_get_shared(&pdev->dev, NULL);
 	if (IS_ERR(bus->rst)) {
 		dev_err(&pdev->dev,
-			"missing or invalid reset controller device tree entry");
+			"missing or invalid reset controller device tree entry\n");
 		return PTR_ERR(bus->rst);
 	}
 	reset_control_deassert(bus->rst);
-- 
2.17.1