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>

1 files changed, 34 insertions, 20 deletions

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index fa66951b05d0..7b098ff5f5dd 100644
--- 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;
         }