[PATCH] i2c: aspeed: Improve driver to support multi-master use cases stably

From: Jae Hyun Yoo
Date: Tue Jun 26 2018 - 12:58:39 EST

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@xxxxxxxxxxxxxxx>
---
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