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Subject: Re: [PATCH i2c-next v6] i2c: aspeed: Handle master/slave combined irq
 events properly
To:     Brendan Higgins <brendanhiggins@google.com>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Joel Stanley <joel@jms.id.au>,
        Andrew Jeffery <andrew@aj.id.au>, linux-i2c@vger.kernel.org,
        OpenBMC Maillist <openbmc@lists.ozlabs.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-aspeed@lists.ozlabs.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        jarkko.nikula@linux.intel.com, james.feist@linux.intel.com,
        vernon.mauery@linux.intel.com
References: <20180823225731.19063-1-jae.hyun.yoo@linux.intel.com>
 <CAFd5g46fRrYW8E8FsPB=5fWSGxemgc4ENc4D2fT7yBfH6p4ERg@mail.gmail.com>
From:   Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Message-ID: <eab56d58-0703-d201-dc9a-f9fd257e96cf@linux.intel.com>
Date:   Thu, 6 Sep 2018 10:32:36 -0700
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On 9/6/2018 10:26 AM, Brendan Higgins wrote:
> 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>
> 

Thanks a lot for your review Brendan!

-Jae