i2c: aspeed: fix master pending state handling

In case of master pending state, it should not trigger a master
command, otherwise data could be corrupted because this H/W shares
the same data buffer for slave and master operations. It also means
that H/W command queue handling is unreliable because of the buffer
sharing issue. To fix this issue, it clears command queue if a
master command is queued in pending state to use S/W solution
instead of H/W command queue handling. Also, it refines restarting
mechanism of the pending master command.

Fixes: 2e57b7cebb98 ("i2c: aspeed: Add multi-master use case support")
Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Acked-by: Joel Stanley <joel@jms.id.au>
Tested-by: Tao Ren <taoren@fb.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index fa66951..7b098ff 100644 (file)
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -108,6 +108,12 @@
 #define ASPEED_I2CD_S_TX_CMD                           BIT(2)
 #define ASPEED_I2CD_M_TX_CMD                           BIT(1)
 #define ASPEED_I2CD_M_START_CMD                                BIT(0)
+#define ASPEED_I2CD_MASTER_CMDS_MASK                                          \
+               (ASPEED_I2CD_M_STOP_CMD |                                      \
+                ASPEED_I2CD_M_S_RX_CMD_LAST |                                 \
+                ASPEED_I2CD_M_RX_CMD |                                        \
+                ASPEED_I2CD_M_TX_CMD |                                        \
+                ASPEED_I2CD_M_START_CMD)
 
 /* 0x18 : I2CD Slave Device Address Register   */
 #define ASPEED_I2CD_DEV_ADDR_MASK                      GENMASK(6, 0)
@@ -336,18 +342,19 @@ static void aspeed_i2c_do_start(struct aspeed_i2c_bus *bus)
        struct i2c_msg *msg = &bus->msgs[bus->msgs_index];
        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)
+       if (bus->slave_state != ASPEED_I2C_SLAVE_INACTIVE) {
                bus->master_state = ASPEED_I2C_MASTER_PENDING;
+               return;
+       }
 #endif /* CONFIG_I2C_SLAVE */
 
+       bus->master_state = ASPEED_I2C_MASTER_START;
        bus->buf_index = 0;
 
        if (msg->flags & I2C_M_RD) {
@@ -422,20 +429,6 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
                }
        }
 
-#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)
@@ -462,11 +455,15 @@ static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
 #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.
+                * master command, clear the queued master command and change
+                * its state to 'pending'. To simplify handling of pending
+                * cases, it uses S/W solution instead of H/W command queue
+                * handling.
                 */
                if (unlikely(irq_status & ASPEED_I2CD_INTR_SLAVE_MATCH)) {
+                       writel(readl(bus->base + ASPEED_I2C_CMD_REG) &
+                               ~ASPEED_I2CD_MASTER_CMDS_MASK,
+                              bus->base + ASPEED_I2C_CMD_REG);
                        bus->master_state = ASPEED_I2C_MASTER_PENDING;
                        dev_dbg(bus->dev,
                                "master goes pending due to a slave start\n");
@@ -629,6 +626,14 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
                        irq_handled |= aspeed_i2c_master_irq(bus,
                                                             irq_remaining);
        }
+
+       /*
+        * Start a pending master command at here if a slave operation is
+        * completed.
+        */
+       if (bus->master_state == ASPEED_I2C_MASTER_PENDING &&
+           bus->slave_state == ASPEED_I2C_SLAVE_INACTIVE)
+               aspeed_i2c_do_start(bus);
 #else
        irq_handled = aspeed_i2c_master_irq(bus, irq_remaining);
 #endif /* CONFIG_I2C_SLAVE */
@@ -691,6 +696,15 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
                     ASPEED_I2CD_BUS_BUSY_STS))
                        aspeed_i2c_recover_bus(bus);
 
+               /*
+                * If timed out and the state is still pending, drop the pending
+                * master command.
+                */
+               spin_lock_irqsave(&bus->lock, flags);
+               if (bus->master_state == ASPEED_I2C_MASTER_PENDING)
+                       bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
+               spin_unlock_irqrestore(&bus->lock, flags);
+
                return -ETIMEDOUT;
        }