Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq events properly

[Brendan Higgins <brendanhiggins@google.com>]

On Thu, Aug 23, 2018 at 3:58 PM Jae Hyun Yoo
<jae.hyun.yoo@linux.intel.com> wrote:
>
> In most of cases, interrupt bits are set one by one but there are
> also a lot of other cases that Aspeed I2C IP sends multiple
> interrupt bits with combining master and slave events using a
> single interrupt call. It happens much more in multi-master
> environment than single-master. For an example, when master is
> waiting for a NORMAL_STOP interrupt in its MASTER_STOP state,
> SLAVE_MATCH and RX_DONE interrupts could come along with the
> NORMAL_STOP in case of an another master immediately sends data
> just after acquiring the bus. In this case, the NORMAL_STOP
> interrupt should be handled by master_irq and the SLAVE_MATCH and
> RX_DONE interrupts should be handled by slave_irq. This commit
> modifies irq hadling logic to handle the master/slave combined
> events properly.
>
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> ---
> Changes since v5:
> - Changed variable names in irq hanlders to represent proper meaning.
> - Fixed an error printing message again to make it use the irq_handled variable.
>
> Changes since v4:
> - Fixed an error printing message that handlers didn't handle all interrupts.
>
> Changes since v3:
> - Fixed typos in a comment.
>
> Changes since v2:
> - Changed the name of ASPEED_I2CD_INTR_ERRORS to ASPEED_I2CD_INTR_MASTER_ERRORS
> - Removed a member irq_status from the struct aspeed_i2c_bus and changed
>   master_irq and slave_irq handlers to make them return status_ack.
> - Added a comment to explain why it needs to try both irq handlers.
>
> Changes since v1:
> - Fixed a grammar issue in commit message.
> - Added a missing line feed character into a message printing.
>
>  drivers/i2c/busses/i2c-aspeed.c | 131 ++++++++++++++++++--------------
>  1 file changed, 76 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index a4f956c6d567..c258c4d9a4c0 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -82,6 +82,11 @@
>  #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_MASTER_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 |                           \
> @@ -227,32 +232,26 @@ 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)
> +static u32 aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>  {
> -       u32 command, irq_status, status_ack = 0;
> +       u32 command, irq_handled = 0;
>         struct i2c_client *slave = bus->slave;
> -       bool irq_handled = true;
>         u8 value;
>
> -       if (!slave) {
> -               irq_handled = false;
> -               goto out;
> -       }
> +       if (!slave)
> +               return 0;
>
>         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) {
> -               status_ack |= ASPEED_I2CD_INTR_SLAVE_MATCH;
> +               irq_handled |= 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 irq_handled;
>
>         dev_dbg(bus->dev, "slave irq status 0x%08x, cmd 0x%08x\n",
>                 irq_status, command);
> @@ -269,31 +268,31 @@ static bool aspeed_i2c_slave_irq(struct aspeed_i2c_bus *bus)
>                                 bus->slave_state =
>                                                 ASPEED_I2C_SLAVE_WRITE_REQUESTED;
>                 }
> -               status_ack |= ASPEED_I2CD_INTR_RX_DONE;
> +               irq_handled |= ASPEED_I2CD_INTR_RX_DONE;
>         }
>
>         /* Slave was asked to stop. */
>         if (irq_status & ASPEED_I2CD_INTR_NORMAL_STOP) {
> -               status_ack |= ASPEED_I2CD_INTR_NORMAL_STOP;
> +               irq_handled |= ASPEED_I2CD_INTR_NORMAL_STOP;
>                 bus->slave_state = ASPEED_I2C_SLAVE_STOP;
>         }
>         if (irq_status & ASPEED_I2CD_INTR_TX_NAK) {
> -               status_ack |= ASPEED_I2CD_INTR_TX_NAK;
> +               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)
>                         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))
>                         dev_err(bus->dev,
>                                 "Expected ACK after processed read.\n");
> @@ -317,13 +316,6 @@ 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:
>         return irq_handled;
>  }
>  #endif /* CONFIG_I2C_SLAVE */
> @@ -380,21 +372,21 @@ static int aspeed_i2c_is_irq_error(u32 irq_status)
>         return 0;
>  }
>
> -static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
> +static u32 aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus, u32 irq_status)
>  {
> -       u32 irq_status, status_ack = 0, command = 0;
> +       u32 irq_handled = 0, command = 0;
>         struct i2c_msg *msg;
>         u8 recv_byte;
>         int ret;
>
> -       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) {
>                 bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
> -               status_ack |= ASPEED_I2CD_INTR_BUS_RECOVER_DONE;
> +               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;
>         }
>
>         /*
> @@ -403,19 +395,22 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
>          * INACTIVE state.
>          */
>         ret = aspeed_i2c_is_irq_error(irq_status);
> -       if (ret < 0) {
> +       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;
>         }
>
>         /* We are in an invalid state; reset bus to a known state. */
>         if (!bus->msgs) {
> -               dev_err(bus->dev, "bus in unknown state\n");
> +               dev_err(bus->dev, "bus in unknown state. irq_status: 0x%x\n",
> +                       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;
>         }
> @@ -428,13 +423,18 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
>          */
>         if (bus->master_state == ASPEED_I2C_MASTER_START) {
>                 if (unlikely(!(irq_status & ASPEED_I2CD_INTR_TX_ACK))) {
> +                       if (unlikely(!(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\n", msg->addr);
> -                       status_ack |= ASPEED_I2CD_INTR_TX_NAK;
> +                       irq_handled |= ASPEED_I2CD_INTR_TX_NAK;
>                         bus->cmd_err = -ENXIO;
>                         aspeed_i2c_do_stop(bus);
>                         goto out_no_complete;
>                 }
> -               status_ack |= ASPEED_I2CD_INTR_TX_ACK;
> +               irq_handled |= ASPEED_I2CD_INTR_TX_ACK;
>                 if (msg->len == 0) { /* SMBUS_QUICK */
>                         aspeed_i2c_do_stop(bus);
>                         goto out_no_complete;
> @@ -449,13 +449,13 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
>         case ASPEED_I2C_MASTER_TX:
>                 if (unlikely(irq_status & ASPEED_I2CD_INTR_TX_NAK)) {
>                         dev_dbg(bus->dev, "slave NACKed TX\n");
> -                       status_ack |= ASPEED_I2CD_INTR_TX_NAK;
> +                       irq_handled |= 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\n");
>                         goto error_and_stop;
>                 }
> -               status_ack |= ASPEED_I2CD_INTR_TX_ACK;
> +               irq_handled |= ASPEED_I2CD_INTR_TX_ACK;
>                 /* fallthrough intended */
>         case ASPEED_I2C_MASTER_TX_FIRST:
>                 if (bus->buf_index < msg->len) {
> @@ -478,7 +478,7 @@ static bool aspeed_i2c_master_irq(struct aspeed_i2c_bus *bus)
>                         dev_err(bus->dev, "master failed to RX\n");
>                         goto error_and_stop;
>                 }
> -               status_ack |= ASPEED_I2CD_INTR_RX_DONE;
> +               irq_handled |= ASPEED_I2CD_INTR_RX_DONE;
>
>                 recv_byte = readl(bus->base + ASPEED_I2C_BYTE_BUF_REG) >> 8;
>                 msg->buf[bus->buf_index++] = recv_byte;
> @@ -506,11 +506,13 @@ 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\n");
> +                       dev_err(bus->dev,
> +                               "master failed to STOP. irq_status:0x%x\n",
> +                               irq_status);
>                         bus->cmd_err = -EIO;
>                         /* Do not STOP as we have already tried. */
>                 } else {
> -                       status_ack |= ASPEED_I2CD_INTR_NORMAL_STOP;
> +                       irq_handled |= ASPEED_I2CD_INTR_NORMAL_STOP;
>                 }
>
>                 bus->master_state = ASPEED_I2C_MASTER_INACTIVE;
> @@ -540,33 +542,52 @@ 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);
> -       return !!irq_status;
> +       return irq_handled;
>  }
>
>  static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
>  {
>         struct aspeed_i2c_bus *bus = dev_id;
> -       bool ret;
> +       u32 irq_received, irq_remaining, irq_handled;
>
>         spin_lock(&bus->lock);
> +       irq_received = readl(bus->base + ASPEED_I2C_INTR_STS_REG);
> +       irq_remaining = irq_received;
>
>  #if IS_ENABLED(CONFIG_I2C_SLAVE)
> -       if (aspeed_i2c_slave_irq(bus)) {
> -               dev_dbg(bus->dev, "irq handled by slave.\n");
> -               ret = true;
> -               goto out;
> +       /*
> +        * In most cases, interrupt bits will be set one by one, although
> +        * multiple interrupt bits could be set at the same time. It's also
> +        * possible that master interrupt bits could be set along with slave
> +        * interrupt bits. Each case needs to be handled using corresponding
> +        * handlers depending on the current state.
> +        */
> +       if (bus->master_state != ASPEED_I2C_MASTER_INACTIVE) {
> +               irq_handled = aspeed_i2c_master_irq(bus, irq_remaining);
> +               irq_remaining &= ~irq_handled;
> +               if (irq_remaining)
> +                       irq_handled |= aspeed_i2c_slave_irq(bus, irq_remaining);
> +       } else {
> +               irq_handled = aspeed_i2c_slave_irq(bus, irq_remaining);
> +               irq_remaining &= ~irq_handled;
> +               if (irq_remaining)
> +                       irq_handled |= aspeed_i2c_master_irq(bus,
> +                                                            irq_remaining);
>         }
> +#else
> +       irq_handled = aspeed_i2c_master_irq(bus, irq_remaining);
>  #endif /* CONFIG_I2C_SLAVE */
>
> -       ret = aspeed_i2c_master_irq(bus);
> +       irq_remaining &= ~irq_handled;
> +       if (irq_remaining)
> +               dev_err(bus->dev,
> +                       "irq handled != irq. expected 0x%08x, but was 0x%08x\n",
> +                       irq_received, irq_handled);
>
> -out:
> +       /* Ack all interrupt bits. */
> +       writel(irq_received, bus->base + ASPEED_I2C_INTR_STS_REG);
>         spin_unlock(&bus->lock);
> -       return ret ? IRQ_HANDLED : IRQ_NONE;
> +       return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
>  }
>
>  static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
> --
> 2.18.0
>

Looks awesome! Thanks!

Reviewed-by: Brendan Higgins <brendanhiggins@google.com>