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Date: Mon, 4 Jun 2018 22:14:48 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Eddie James <eajames@...ux.vnet.ibm.com>
Cc: linux-i2c <linux-i2c@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
devicetree <devicetree@...r.kernel.org>,
Wolfram Sang <wsa@...-dreams.de>,
Rob Herring <robh+dt@...nel.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Joel Stanley <joel@....id.au>,
Mark Rutland <mark.rutland@....com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v9 5/7] i2c: fsi: Add transfer implementation
On Mon, Jun 4, 2018 at 10:00 PM, Eddie James <eajames@...ux.vnet.ibm.com> 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@...ux.vnet.ibm.com>
> ---
> 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?
> + 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.
> + 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?
> +
> + 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
>
--
With Best Regards,
Andy Shevchenko
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