Re: [PATCH v9 5/7] i2c: fsi: Add transfer implementation

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On 06/04/2018 02:14 PM, Andy Shevchenko wrote:
On Mon, Jun 4, 2018 at 10:00 PM, Eddie James <eajames@xxxxxxxxxxxxxxxxxx> wrote:
Execute I2C transfers from the FSI-attached I2C master. Use polling
instead of interrupts as we have no hardware IRQ over FSI.

Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxxxxxxx>
---
  drivers/i2c/busses/i2c-fsi.c | 195 ++++++++++++++++++++++++++++++++++++++++++-
  1 file changed, 193 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
index 101b9c5..4e5964e 100644
--- a/drivers/i2c/busses/i2c-fsi.c
+++ b/drivers/i2c/busses/i2c-fsi.c
@@ -150,6 +150,7 @@ struct fsi_i2c_port {
         struct i2c_adapter      adapter;
         struct fsi_i2c_master   *master;
         u16                     port;
+       u16                     xfrd;
  };

  static int fsi_i2c_read_reg(struct fsi_device *fsi, unsigned int reg,
@@ -225,6 +226,99 @@ static int fsi_i2c_set_port(struct fsi_i2c_port *port)
         return fsi_i2c_write_reg(fsi, I2C_FSI_RESET_ERR, &dummy);
  }

+static int fsi_i2c_start(struct fsi_i2c_port *port, struct i2c_msg *msg,
+                        bool stop)
+{
+       struct fsi_i2c_master *i2c = port->master;
+       u32 cmd = I2C_CMD_WITH_START | I2C_CMD_WITH_ADDR;
+
+       port->xfrd = 0;
+
+       if (msg->flags & I2C_M_RD)
+               cmd |= I2C_CMD_READ;
+
+       if (stop || msg->flags & I2C_M_STOP)
+               cmd |= I2C_CMD_WITH_STOP;
+
+       cmd |= FIELD_PREP(I2C_CMD_ADDR, msg->addr >> 1);
Did you consider to unify READ + ADDR as ADDR_8BIT?

Yes, however the result from the i2c_8bit_addr_from_msg function is not equivalent. This hardware expects the 8-bit address to be concatenated with the read/not write bit. Also the function returns a u8, which won't work for addresses with bit 7 set, since it left-shifts by one.


+       cmd |= FIELD_PREP(I2C_CMD_LEN, msg->len);
+
+       return fsi_i2c_write_reg(i2c->fsi, I2C_FSI_CMD, &cmd);
+}
+
+static int fsi_i2c_get_op_bytes(int op_bytes)
+{
+       /* fsi is limited to max 4 byte aligned ops */
+       if (op_bytes > 4)
+               return 4;
+       else if (op_bytes == 3)
Since you dropped one of 'else', another also is not needed.

True.


+               return 2;
+       return op_bytes;
+}
+
+static int fsi_i2c_write_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
+                             u8 fifo_count)
+{
+       int write;
+       int rc;
+       struct fsi_i2c_master *i2c = port->master;
+       int bytes_to_write = i2c->fifo_size - fifo_count;
+       int bytes_remaining = msg->len - port->xfrd;
+
+       bytes_to_write = min(bytes_to_write, bytes_remaining);
+
+       while (bytes_to_write) {
+               write = fsi_i2c_get_op_bytes(bytes_to_write);
+
+               rc = fsi_device_write(i2c->fsi, I2C_FSI_FIFO,
+                                     &msg->buf[port->xfrd], write);
+               if (rc)
+                       return rc;
+
+               port->xfrd += write;
+               bytes_to_write -= write;
+       }
Just to be sure, if by some reason write == 0 in the loop for a while,
would it become infinite loop?

It's not possible that write == 0. Same for read below.

Thanks,
Eddie


+
+       return 0;
+}
+
+static int fsi_i2c_read_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
+                            u8 fifo_count)
+{
+       int read;
+       int rc;
+       struct fsi_i2c_master *i2c = port->master;
+       int bytes_to_read;
+       int xfr_remaining = msg->len - port->xfrd;
+       u32 dummy;
+
+       bytes_to_read = min_t(int, fifo_count, xfr_remaining);
+
+       while (bytes_to_read) {
+               read = fsi_i2c_get_op_bytes(bytes_to_read);
+
+               if (xfr_remaining) {
+                       rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO,
+                                            &msg->buf[port->xfrd], read);
+                       if (rc)
+                               return rc;
+
+                       port->xfrd += read;
+                       xfr_remaining -= read;
+               } else {
+                       /* no more buffer but data in fifo, need to clear it */
+                       rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO, &dummy,
+                                            read);
+                       if (rc)
+                               return rc;
+               }
+
+               bytes_to_read -= read;
+       }
Ditto for read == 0.

+
+       return 0;
+}
+
  static int fsi_i2c_reset_bus(struct fsi_i2c_master *i2c)
  {
         int i, rc;
@@ -388,17 +482,114 @@ static int fsi_i2c_abort(struct fsi_i2c_port *port, u32 status)
         return -ETIMEDOUT;
  }

+static int fsi_i2c_handle_status(struct fsi_i2c_port *port,
+                                struct i2c_msg *msg, u32 status)
+{
+       int rc;
+       u8 fifo_count;
+
+       if (status & I2C_STAT_ERR) {
+               rc = fsi_i2c_abort(port, status);
+               if (rc)
+                       return rc;
+
+               if (status & I2C_STAT_INV_CMD)
+                       return -EINVAL;
+
+               if (status & (I2C_STAT_PARITY | I2C_STAT_BE_OVERRUN |
+                   I2C_STAT_BE_ACCESS))
+                       return -EPROTO;
+
+               if (status & I2C_STAT_NACK)
+                       return -ENXIO;
+
+               if (status & I2C_STAT_LOST_ARB)
+                       return -EAGAIN;
+
+               if (status & I2C_STAT_STOP_ERR)
+                       return -EBADMSG;
+
+               return -EIO;
+       }
+
+       if (status & I2C_STAT_DAT_REQ) {
+               fifo_count = FIELD_GET(I2C_STAT_FIFO_COUNT, status);
+
+               if (msg->flags & I2C_M_RD)
+                       return fsi_i2c_read_fifo(port, msg, fifo_count);
+
+               return fsi_i2c_write_fifo(port, msg, fifo_count);
+       }
+
+       if (status & I2C_STAT_CMD_COMP) {
+               if (port->xfrd < msg->len)
+                       return -ENODATA;
+
+               return msg->len;
+       }
+
+       return 0;
+}
+
+static int fsi_i2c_wait(struct fsi_i2c_port *port, struct i2c_msg *msg,
+                       unsigned long timeout)
+{
+       u32 status = 0;
+       int rc;
+       unsigned long start = jiffies;
+
+       do {
+               rc = fsi_i2c_read_reg(port->master->fsi, I2C_FSI_STAT,
+                                     &status);
+               if (rc)
+                       return rc;
+
+               if (status & I2C_STAT_ANY_RESP) {
+                       rc = fsi_i2c_handle_status(port, msg, status);
+                       if (rc < 0)
+                               return rc;
+
+                       /* cmd complete and all data xfrd */
+                       if (rc == msg->len)
+                               return 0;
+
+                       /* need to xfr more data, but maybe don't need wait */
+                       continue;
+               }
+
+               usleep_range(I2C_CMD_SLEEP_MIN_US, I2C_CMD_SLEEP_MAX_US);
+       } while (time_after(start + timeout, jiffies));
+
+       return -ETIMEDOUT;
+}
+
  static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                         int num)
  {
-       int rc;
+       int i, rc;
+       unsigned long start_time;
         struct fsi_i2c_port *port = adap->algo_data;
+       struct i2c_msg *msg;

         rc = fsi_i2c_set_port(port);
         if (rc)
                 return rc;

-       return -EOPNOTSUPP;
+       for (i = 0; i < num; i++) {
+               msg = msgs + i;
+               start_time = jiffies;
+
+               rc = fsi_i2c_start(port, msg, i == num - 1);
+               if (rc)
+                       return rc;
+
+               rc = fsi_i2c_wait(port, msg,
+                                 adap->timeout - (jiffies - start_time));
+               if (rc)
+                       return rc;
+       }
+
+       return 0;
  }

  static u32 fsi_i2c_functionality(struct i2c_adapter *adap)
--
1.8.3.1




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