RE: [PATCH 2/2] i2c: qup: Fixed the DMA segments length

[Abhishek Sahu]

On 2016-05-11 21:48, Sricharan wrote:
> Hi,
>
> > 1. The current QCOM I2C driver code is failing for transfer length 
> > greater
> > than 255. This is happening due to improper segments length as the I2C 
> > DMA
> > segments can be maximum of 256 bytes.
> >
> > 2. The transfer length tlen was being initialized with 0 for 256 
> > bytes,
> > which is
> > being passed for DMA mappings resulting in improper DMA mapping 
> > length.
> >
> > This patch fixes the above said problems by initializing the block 
> > count
> > with
> > the values calculated in qup_i2c_set_blk_data and calculating the
> remaining
> > length for last DMA segment. Also, the block data length need to be
> > decremented after each transfer. Additionally, this patch corrects the
> > tlen
> > assignment for DMA mapping.
> >
> > Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
> > ---
> >  drivers/i2c/busses/i2c-qup.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-qup.c 
> > b/drivers/i2c/busses/i2c-qup.c
> > index
> > 8c2f1bc..6d6b7dc 100644
> > --- a/drivers/i2c/busses/i2c-qup.c
> > +++ b/drivers/i2c/busses/i2c-qup.c
> > @@ -651,23 +651,24 @@ static int qup_i2c_bam_do_xfer(struct
> > qup_i2c_dev *qup, struct i2c_msg *msg,
> >  	u8 *tags;
> >
> >  	while (idx < num) {
> > -		blocks = (msg->len + limit) / limit;
> > -		rem = msg->len % limit;
> >  		tx_len = 0, len = 0, i = 0;
> >
> >  		qup->is_last = (idx == (num - 1));
> >
> >  		qup_i2c_set_blk_data(qup, msg);
> >
> > +		blocks = qup->blk.count;
> > +		rem = msg->len - (blocks - 1) * limit;
> > +
>       Same if we had blocks = (msg->len + limit - 1) / limit instead of 
> the
> above ?
Yes. We calculating this inside qup_i2c_set_blk_data and assigning the 
same value to
qup->blk.count so I am using this to avoid redundant arithmetic 
operations.
>      Otherwise,
>      Reviewed-by: Sricharan@xxxxxxxxxxxxxx
>
> Regards,
>  Sricharan

--
Abhishek Sahu