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Subject[PATCH v2] i2c: aspeed: Add multi-master use case support
Date
In multi-master environment, this driver's master cannot know
exactly when a peer master sends data to this driver's slave so
cases can be happened that this master tries sending data through
the master_xfer function but slave data from a peer master is still
being processed or slave xfer is started by a peer immediately
after it queues a master command. To support multi-master use cases
properly, this H/W provides arbitration in physical level and it
provides priority based command handling too to avoid conflicts in
multi-master environment, means that if a master and a slave events
happen at the same time, H/W will handle a higher priority event
first and a pending event will be handled when bus comes back to
the idle state.

To support this H/W feature properly, this patch adds the 'pending'
state of master and its handling code so that the pending master
xfer can be continued after slave operation properly.

Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
---
Changes since v9:
* Removed cppcheck warnings.

drivers/i2c/busses/i2c-aspeed.c | 119 +++++++++++++++++++++++++-------
1 file changed, 93 insertions(+), 26 deletions(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 8dc9161ced38..882c4ab1d18a 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -117,6 +117,7 @@

enum aspeed_i2c_master_state {
ASPEED_I2C_MASTER_INACTIVE,
+ ASPEED_I2C_MASTER_PENDING,
ASPEED_I2C_MASTER_START,
ASPEED_I2C_MASTER_TX_FIRST,
ASPEED_I2C_MASTER_TX,
@@ -126,12 +127,13 @@ enum aspeed_i2c_master_state {
};

enum aspeed_i2c_slave_state {
- ASPEED_I2C_SLAVE_STOP,
+ ASPEED_I2C_SLAVE_INACTIVE,
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 {
@@ -156,6 +158,8 @@ struct aspeed_i2c_bus {
int cmd_err;
/* Protected only by i2c_lock_bus */
int master_xfer_result;
+ /* Multi-master */
+ bool multi_master;
#if IS_ENABLED(CONFIG_I2C_SLAVE)
struct i2c_client *slave;
enum aspeed_i2c_slave_state slave_state;
@@ -251,7 +255,7 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
}

/* Slave is not currently active, irq was for someone else. */
- if (bus->slave_state == ASPEED_I2C_SLAVE_STOP)
+ if (bus->slave_state == ASPEED_I2C_SLAVE_INACTIVE)
return irq_handled;

dev_dbg(bus->dev, "slave irq status 0x%08x, cmd 0x%08x\n",
@@ -277,16 +281,15 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
irq_handled |= ASPEED_I2CD_INTR_NORMAL_STOP;
bus->slave_state = ASPEED_I2C_SLAVE_STOP;
}
- if (irq_status & ASPEED_I2CD_INTR_TX_NAK) {
+ if (irq_status & ASPEED_I2CD_INTR_TX_NAK &&
+ bus->slave_state == ASPEED_I2C_SLAVE_READ_PROCESSED) {
irq_handled |= ASPEED_I2CD_INTR_TX_NAK;
bus->slave_state = ASPEED_I2C_SLAVE_STOP;
}
- if (irq_status & ASPEED_I2CD_INTR_TX_ACK)
- irq_handled |= ASPEED_I2CD_INTR_TX_ACK;

switch (bus->slave_state) {
case ASPEED_I2C_SLAVE_READ_REQUESTED:
- if (irq_status & ASPEED_I2CD_INTR_TX_ACK)
+ if (unlikely(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);
@@ -294,9 +297,12 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
writel(ASPEED_I2CD_S_TX_CMD, bus->base + ASPEED_I2C_CMD_REG);
break;
case ASPEED_I2C_SLAVE_READ_PROCESSED:
- if (!(irq_status & ASPEED_I2CD_INTR_TX_ACK))
+ if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
dev_err(bus->dev,
"Expected ACK after processed read.\n");
+ break;
+ }
+ irq_handled |= ASPEED_I2CD_INTR_TX_ACK;
i2c_slave_event(slave, I2C_SLAVE_READ_PROCESSED, &value);
writel(value, bus->base + ASPEED_I2C_BYTE_BUF_REG);
writel(ASPEED_I2CD_S_TX_CMD, bus->base + ASPEED_I2C_CMD_REG);
@@ -310,10 +316,15 @@ static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
break;
case ASPEED_I2C_SLAVE_STOP:
i2c_slave_event(slave, I2C_SLAVE_STOP, &value);
+ bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
+ break;
+ case ASPEED_I2C_SLAVE_START:
+ /* Slave was just started. Waiting for the next event. */;
break;
default:
- dev_err(bus->dev, "unhandled slave_state: %d\n",
+ dev_err(bus->dev, "unknown slave_state: %d\n",
bus->slave_state);
+ bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
break;
}

@@ -329,6 +340,17 @@ static void aspeed_i2c_do_start(struct aspeed_i2c_bus *bus)
u8 slave_addr = i2c_8bit_addr_from_msg(msg);

bus->master_state = ASPEED_I2C_MASTER_START;
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+ /*
+ * If it's requested in the middle of a slave session, set the master
+ * state to 'pending' then H/W will continue handling this master
+ * command when the bus comes back to the idle state.
+ */
+ if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE)
+ bus->master_state = ASPEED_I2C_MASTER_PENDING;
+#endif /* CONFIG_I2C_SLAVE */
+
bus->buf_index = 0;

if (msg->flags & I2C_M_RD) {
@@ -384,10 +406,6 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
irq_handled |= 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;
}

/*
@@ -399,11 +417,32 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
if (ret) {
dev_dbg(bus->dev, "received error interrupt: 0x%08x\n",
irq_status);
- bus->cmd_err = ret;
- bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
irq_handled |= (irq_status & ASPEED_I2CD_INTR_MASTER_ERRORS);
- goto out_complete;
+ if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE) {
+ bus->cmd_err = ret;
+ bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
+ goto out_complete;
+ }
+ }
+
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+ /*
+ * A pending master command will be started by H/W when the bus comes
+ * back to idle state after completing a slave operation so change the
+ * master state from 'pending' to 'start' at here if slave is inactive.
+ */
+ if (bus->master_state == ASPEED_I2C_MASTER_PENDING) {
+ if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE)
+ goto out_no_complete;
+
+ bus->master_state = ASPEED_I2C_MASTER_START;
}
+#endif /* CONFIG_I2C_SLAVE */
+
+ /* Master is not currently active, irq was for someone else. */
+ if (bus->master_state == ASPEED_I2C_MASTER_INACTIVE ||
+ bus->master_state == ASPEED_I2C_MASTER_PENDING)
+ goto out_no_complete;

/* We are in an invalid state; reset bus to a known state. */
if (!bus->msgs) {
@@ -423,6 +462,20 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
* then update the state and handle the new state below.
*/
if (bus->master_state == ASPEED_I2C_MASTER_START) {
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+ /*
+ * If a peer master starts a xfer immediately after it queues a
+ * master command, change its state to 'pending' then H/W will
+ * continue the queued master xfer just after completing the
+ * slave mode session.
+ */
+ if (unlikely(irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH)) {
+ bus->master_state = ASPEED_I2C_MASTER_PENDING;
+ dev_dbg(bus->dev,
+ "master goes pending due to a slave start\n");
+ goto out_no_complete;
+ }
+#endif /* CONFIG_I2C_SLAVE */
if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_NAK))) {
bus->cmd_err = -ENXIO;
@@ -566,7 +619,8 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
* interrupt bits. Each case needs to be handled using corresponding
* handlers depending on the current state.
*/
- if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE) {
+ if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE &&
+ bus->master_state != ASPEED_I2C_MASTER_PENDING) {
irq_handled = aspeed_i2c_master_irq(bus, irq_remaining);
irq_remaining &= ~irq_handled;
if (irq_remaining)
@@ -601,15 +655,16 @@ 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) {
+ /* If bus is busy in a single master environment, attempt recovery. */
+ if (!bus->multi_master &&
+ (readl(bus->base + ASPEED_I2C_CMD_REG) &
+ ASPEED_I2CD_BUS_BUSY_STS)) {
+ int ret;
+
spin_unlock_irqrestore(&bus->lock, flags);
ret = aspeed_i2c_recover_bus(bus);
if (ret)
@@ -629,10 +684,20 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
time_left = wait_for_completion_timeout(&bus->cmd_complete,
bus->adap.timeout);

- if (time_left == 0)
+ if (time_left == 0) {
+ /*
+ * If timed out and bus is still busy in a multi master
+ * environment, attempt recovery at here.
+ */
+ if (bus->multi_master &&
+ (readl(bus->base + ASPEED_I2C_CMD_REG) &
+ ASPEED_I2CD_BUS_BUSY_STS))
+ aspeed_i2c_recover_bus(bus);
+
return -ETIMEDOUT;
- else
- return bus->master_xfer_result;
+ }
+
+ return bus->master_xfer_result;
}

static u32 aspeed_i2c_functionality(struct i2c_adapter *adap)
@@ -672,7 +737,7 @@ static int aspeed_i2c_reg_slave(struct i2c_client *client)
__aspeed_i2c_reg_slave(bus, client->addr);

bus->slave = client;
- bus->slave_state = ASPEED_I2C_SLAVE_STOP;
+ bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
spin_unlock_irqrestore(&bus->lock, flags);

return 0;
@@ -827,7 +892,9 @@ static int aspeed_i2c_init(struct aspeed_i2c_bus *bus,
if (ret < 0)
return ret;

- if (!of_property_read_bool(pdev->dev.of_node, "multi-master"))
+ if (of_property_read_bool(pdev->dev.of_node, "multi-master"))
+ bus->multi_master = true;
+ else
fun_ctrl_reg |= ASPEED_I2CD_MULTI_MASTER_DIS;

/* Enable Master Mode */
--
2.20.1
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