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

["Christ, Austin" <austinwc@codeaurora.org>]

Hello,


On 5/25/2016 3:31 AM, rajeev kumar wrote:
> On Fri, May 20, 2016 at 3:14 AM, Austin Christ <austinwc@codeaurora.org> wrote:
>> From: Naveen Kaje <nkaje@codeaurora.org>
>>
>> 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@codeaurora.org>
>> Signed-off-by: Austin Christ <austinwc@codeaurora.org>
>> ---
>>   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