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

[Naveen Kaje]

On 5/10/2016 1:13 AM, Sricharan wrote:
> +additional lists
>
> > 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>
> > ---
> >   drivers/i2c/busses/i2c-qup.c | 95 ++++++++++++++++++++++++++++++-------
> > -------
> >   1 file changed, 66 insertions(+), 29 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qup.c b/drivers/i2c/busses/i2c-qup.c
> index
> > ef31b26..2658b67 100644
> > --- a/drivers/i2c/busses/i2c-qup.c
> > +++ b/drivers/i2c/busses/i2c-qup.c
> > @@ -526,38 +526,49 @@ 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);
> >
> > -	if (qup->blk.pos == 0) {
> > -		tags[len++] = QUP_TAG_V2_START;
> > -		tags[len++] = addr & 0xff;
> > +	/* Handle SMBus block data read */
> > +	if ((msg->flags & I2C_M_RD) && (msg->flags & I2C_M_RECV_LEN)
> > &&
> > +	    (msg->len > 1)) {
> > +		tags[len++] = QUP_TAG_V2_DATARD_STOP;
> > +		data_len = qup_i2c_get_data_len(qup);
> > +		tags[len++] = data_len - 1;
> > +	} else {
> > +		if (qup->blk.pos == 0) {
> > +			tags[len++] = QUP_TAG_V2_START;
> > +			tags[len++] = addr & 0xff;
> >
> > -		if (msg->flags & I2C_M_TEN)
> > -			tags[len++] = addr >> 8;
> > -	}
> > +			if (msg->flags & I2C_M_TEN)
> > +				tags[len++] = addr >> 8;
> > +		}
> >
> > -	/* Send _STOP commands for the last block */
> > -	if (last) {
> > -		if (msg->flags & I2C_M_RD)
> > -			tags[len++] = QUP_TAG_V2_DATARD_STOP;
> > -		else
> > -			tags[len++] = QUP_TAG_V2_DATAWR_STOP;
> > -	} else {
> > -		if (msg->flags & I2C_M_RD)
> > +		/* Send _STOP commands for the last block */
> > +		if ((msg->flags & I2C_M_RD)
> > +			&& (msg->flags & I2C_M_RECV_LEN)) {
> >   			tags[len++] = QUP_TAG_V2_DATARD;
> > -		else
> > -			tags[len++] = QUP_TAG_V2_DATAWR;
> > -	}
> > +		} else if (last) {
> > +			if (msg->flags & I2C_M_RD)
> > +				tags[len++] = QUP_TAG_V2_DATARD_STOP;
> > +			else
> > +				tags[len++] = QUP_TAG_V2_DATAWR_STOP;
> > +		} else {
> > +			if (msg->flags & I2C_M_RD)
> > +				tags[len++] = QUP_TAG_V2_DATARD;
> > +			else
> > +				tags[len++] = QUP_TAG_V2_DATAWR;
> > +		}
> >
> > -	data_len = qup_i2c_get_data_len(qup);
> > +		data_len = qup_i2c_get_data_len(qup);
> >
> > -	/* 0 implies 256 bytes */
> > -	if (data_len == QUP_READ_LIMIT)
> > -		tags[len++] = 0;
> > -	else
> > -		tags[len++] = data_len;
> > +		/* 0 implies 256 bytes */
> > +		if (data_len == QUP_READ_LIMIT)
> > +			tags[len++] = 0;
> > +		else
> > +			tags[len++] = data_len;
> >
> > -	if ((msg->flags & I2C_M_RD) && last && is_dma) {
> > -		tags[len++] = QUP_BAM_INPUT_EOT;
> > -		tags[len++] = QUP_BAM_FLUSH_STOP;
> > +		if ((msg->flags & I2C_M_RD) && last && is_dma) {
> > +			tags[len++] = QUP_BAM_INPUT_EOT;
> > +			tags[len++] = QUP_BAM_FLUSH_STOP;
> > +		}
> >   	}
>     Will it look simpler if we add a qup_i2c_set_tags_smb instead and add an
>     Comment ? Here it is not clear how this is different from a normal read.
Will rework this and send V2.
> <snip..>
>
> > +
> > +		/* Handle SMBus block read length */
> > +		if ((msg->flags & I2C_M_RECV_LEN) && (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);
> > +			qup_i2c_issue_xfer_v2(qup, msg);
> > +			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);
>         
>           When v2 mode is not supported this should return an error,
>           in qup_i2c_xfer for msg->flags & I2C_M_RECV_LEN
Will add a check in qup_i2c_xfer in the next version of the patch.
> Regards,
>   Sricharan