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Date: Mon, 4 Jun 2018 14:37:01 -0500
From: Eddie James <eajames@...ux.vnet.ibm.com>
To: Andy Shevchenko <andy.shevchenko@...il.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 06/04/2018 02:14 PM, Andy Shevchenko wrote:
> 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?
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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