Re: [PATCH v3 2/2] i2c: qup: support SMBus block read

[Christ, Austin]

Hello,


On 5/25/2016 3:31 AM, rajeev kumar wrote:
> On Fri, May 20, 2016 at 3:14 AM, Austin Christ <austinwc@xxxxxxxxxxxxxx> wrote:
> > From: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
> >
> > I2C QUP driver relies on SMBus emulation support from the framework.
> > To handle SMBus block reads, the driver should check I2C_M_RECV_LEN
> > flag and should read the first byte received as the message length.
> >
> > The driver configures the QUP hardware to read one byte. Once the
> > message length is known from this byte, the QUP hardware is configured
> > to read the rest.
> >
> > Signed-off-by: Naveen Kaje <nkaje@xxxxxxxxxxxxxx>
> > Signed-off-by: Austin Christ <austinwc@xxxxxxxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-qup.c | 68 ++++++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 65 insertions(+), 3 deletions(-)
> >
> > Changes:
> > - v3:
> >   - clean up redundant checks
> >   - use constant instead of variable for smbus length field
> > - v2:
> >   - rework the smbus block read and break into separate function
> >
> > diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> > index ea6ca5f..9fbed83 100644
> > --- a/drivers/i2c/busses/i2c-qup.c
> > +++ b/drivers/i2c/busses/i2c-qup.c
> > @@ -517,6 +517,33 @@ static int qup_i2c_get_data_len(struct qup_i2c_dev *qup)
> >          return data_len;
> >   }
> >
> > +static bool qup_i2c_check_msg_len(struct i2c_msg *msg)
> > +{
> > +       return ((msg->flags & I2C_M_RD) && (msg->flags & I2C_M_RECV_LEN));
> > +}
> > +
> > +static int qup_i2c_set_tags_smb(u16 addr, u8 *tags, struct qup_i2c_dev *qup,
> > +                       struct i2c_msg *msg)
> > +{
> > +       int len = 0;
> > +
> > +       if (msg->len > 1) {
> > +               tags[len++] = QUP_TAG_V2_DATARD_STOP;
> > +               tags[len++] = qup_i2c_get_data_len(qup) - 1;
> > +       } else {
> > +               tags[len++] = QUP_TAG_V2_START;
> > +               tags[len++] = addr & 0xff;
> > +
> > +               if (msg->flags & I2C_M_TEN)
> > +                       tags[len++] = addr >> 8;
> > +
> > +               tags[len++] = QUP_TAG_V2_DATARD;
> > +               /* Read 1 byte indicating the length of the SMBus message */
> > +               tags[len++] = 1;
> > +       }
> > +       return len;
> > +}
> > +
> >   static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
> >                              struct i2c_msg *msg,  int is_dma)
> >   {
> > @@ -526,6 +553,10 @@ static int qup_i2c_set_tags(u8 *tags, struct qup_i2c_dev *qup,
> >
> >          int last = (qup->blk.pos == (qup->blk.count - 1)) && (qup->is_last);
> >
> > +       /* Handle tags for SMBus block read */
> > +       if (qup_i2c_check_msg_len(msg))
> > +               return qup_i2c_set_tags_smb(addr, tags, qup, msg);
> > +
> >          if (qup->blk.pos == 0) {
> >                  tags[len++] = QUP_TAG_V2_START;
> >                  tags[len++] = addr & 0xff;
> > @@ -1065,9 +1096,17 @@ static int qup_i2c_read_fifo_v2(struct qup_i2c_dev *qup,
> >                                  struct i2c_msg *msg)
> >   {
> >          u32 val;
> > -       int idx, pos = 0, ret = 0, total;
> > +       int idx, pos = 0, ret = 0, total, msg_offset = 0;
> >
> > +       /*
> > +        * If the message length is already read in
> > +        * the first byte of the buffer, account for
> > +        * that by setting the offset
> > +        */
> > +       if (qup_i2c_check_msg_len(msg) && (msg->len > 1))
> > +               msg_offset = 1;
> >          total = qup_i2c_get_data_len(qup);
> > +       total -= msg_offset;
> >
> >          /* 2 extra bytes for read tags */
> >          while (pos < (total + 2)) {
> > @@ -1087,8 +1126,8 @@ static int qup_i2c_read_fifo_v2(struct qup_i2c_dev *qup,
> >
> >                          if (pos >= (total + 2))
> >                                  goto out;
> > -
> > -                       msg->buf[qup->pos++] = val & 0xff;
> > +                       msg->buf[qup->pos + msg_offset] = val & 0xff;
> > +                       qup->pos++;
> >                  }
> >          }
> >
> > @@ -1128,6 +1167,24 @@ static int qup_i2c_read_one_v2(struct qup_i2c_dev *qup, struct i2c_msg *msg)
> >                          goto err;
> >
> >                  qup->blk.pos++;
> > +
> > +               /* Handle SMBus block read length */
> > +               if (qup_i2c_check_msg_len(msg) && (msg->len == 1)) {
> > +                       if (msg->buf[0] > I2C_SMBUS_BLOCK_MAX) {
> > +                               ret = -EPROTO;
> > +                               goto err;
> > +                       }
> > +                       msg->len += msg->buf[0];
> > +                       qup->pos = 0;
> > +                       qup_i2c_set_read_mode_v2(qup, msg->len);
> > +                       ret = qup_i2c_issue_xfer_v2(qup, msg);
> > +                       if (ret)
> > +                               goto err;
> > +                       ret = qup_i2c_wait_for_complete(qup, msg);
> > +                       if (ret)
> > +                               goto err;
> > +                       qup_i2c_set_blk_data(qup, msg);
> > +               }
> >          } while (qup->blk.pos < qup->blk.count);
> >
> >   err:
> > @@ -1210,6 +1267,11 @@ static int qup_i2c_xfer(struct i2c_adapter *adap,
> >                          goto out;
> >                  }
> >
> > +               if (qup_i2c_check_msg_len(&msgs[idx])) {
> > +                       ret = -EOPNOTSUPP;
> Could you please rethink on this return value ? It should not be "EOPNOTSUPP"
>
> ~Rajeev

This will be replaced with "EINVAL" in v4 patches.
> > +                       goto out;
> > +               }
> > +
> >                  if (msgs[idx].flags & I2C_M_RD)
> >                          ret = qup_i2c_read_one(qup, &msgs[idx]);
> >                  else
> > --
> > Qualcomm Innovation Center, Inc.
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > a Linux Foundation Collaborative Project.
> >
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Thanks,
Austin