Re: [PATCH] i2c: brcmstb: Fix START and STOP conditions

[Jaedon Shin <jaedon.shin@gmail.com>]

Hi Kamal, Florian,

> On 3 Mar 2017, at 3:48 AM, Florian Fainelli <f.fainelli@gmail.com> wrote:
> 
> On 03/02/2017 10:42 AM, Kamal Dasu wrote:
>> Jaedon,
>> 
>> On Fri, Aug 12, 2016 at 1:56 AM, Jaedon Shin <jaedon.shin@gmail.com> wrote:
>>> Fixes always repeated START when process multiple bytes with a message
>>> in combined transactions.
>>> 
>>> The BSC has multiple data stroage that send or receive data at once, and
>>> it has the RESTART, NOSTART, NOSTOP to the condition flags. The problem
>>> is that begin repeated START for all the messages in combined
>>> transaction. If length of a data is over 32bytes, The BSC transmit
>>> repeated START in every 32bytes.
>>> 
>> 
>> Can you rephrase the commit message to something  like below ?
>> 
>> The BSC data buffers to send and receive data are each of size 32 bytes
>> or 8 bytes 'xfersz' depending on SoC. The problem observed for all the
>> combined message transfer was if length of data transfer was a multiple of
>> 'xfersz'  a repeated START was being transmitted by BSC driver. Fixed this
>> by appropriately setting START/STOP conditions for such transfers.
>> 

No problem.

>>> Fixes always repeated START when process multiple bytes with a message
>>> in combined transactions.
>>> 
>>> The BSC has multiple data stroage that send or receive data at once, and
>>> it has the RESTART, NOSTART, NOSTOP to the condition flags. The problem
>>> is that begin repeated START for all the messages in combined
>>> transaction. If length of a data is over 32bytes, The BSC transmit
>>> repeated START in every 32bytes.
>> 
>> The changes looks good to me.
> 
> Do you mind adding:
> 
> Fixes: dd1aa2524bc5 ("i2c: brcmstb: Add Broadcom settop SoC i2c
> controller driver")
> 

Add that also.

Thanks,
Jaedon

> so this can be backported to -stable tree as well? Thanks!
> 
>> 
>>> Signed-off-by: Jaedon Shin <jaedon.shin@gmail.com>
>>> ---
>>> drivers/i2c/busses/i2c-brcmstb.c | 27 +++++++++++++++++++++------
>>> 1 file changed, 21 insertions(+), 6 deletions(-)
>>> 
>>> diff --git a/drivers/i2c/busses/i2c-brcmstb.c b/drivers/i2c/busses/i2c-brcmstb.c
>>> index 3f5a4d71d3bf..51c5f0bd361d 100644
>>> --- a/drivers/i2c/busses/i2c-brcmstb.c
>>> +++ b/drivers/i2c/busses/i2c-brcmstb.c
>>> @@ -465,6 +465,7 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
>>>        u8 *tmp_buf;
>>>        int len = 0;
>>>        int xfersz = brcmstb_i2c_get_xfersz(dev);
>>> +       u32 cond, cond_per_msg;
>>> 
>>>        if (dev->is_suspended)
>>>                return -EBUSY;
>>> @@ -481,10 +482,11 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
>>>                        pmsg->buf ? pmsg->buf[0] : '0', pmsg->len);
>>> 
>>>                if (i < (num - 1) && (msgs[i + 1].flags & I2C_M_NOSTART))
>>> -                       brcmstb_set_i2c_start_stop(dev, ~(COND_START_STOP));
>>> +                       cond = ~COND_START_STOP;
>>>                else
>>> -                       brcmstb_set_i2c_start_stop(dev,
>>> -                                                  COND_RESTART | COND_NOSTOP);
>>> +                       cond = COND_RESTART | COND_NOSTOP;
>>> +
>>> +               brcmstb_set_i2c_start_stop(dev, cond);
>>> 
>>>                /* Send slave address */
>>>                if (!(pmsg->flags & I2C_M_NOSTART)) {
>>> @@ -497,13 +499,24 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
>>>                        }
>>>                }
>>> 
>>> +               cond_per_msg = cond;
>>> +
>>>                /* Perform data transfer */
>>>                while (len) {
>>>                        bytes_to_xfer = min(len, xfersz);
>>> 
>>> -                       if (len <= xfersz && i == (num - 1))
>>> -                               brcmstb_set_i2c_start_stop(dev,
>>> -                                                          ~(COND_START_STOP));
>>> +                       if (len <= xfersz) {
>>> +                               if (i == (num - 1))
>>> +                                       cond_per_msg = cond_per_msg &
>>> +                                               ~(COND_RESTART | COND_NOSTOP);
>>> +                               else
>>> +                                       cond_per_msg = cond;
>>> +                       } else {
>>> +                               cond_per_msg = (cond_per_msg & ~COND_RESTART) |
>>> +                                       COND_NOSTOP;
>>> +                       }
>>> +
>>> +                       brcmstb_set_i2c_start_stop(dev, cond_per_msg);
>>> 
>>>                        rc = brcmstb_i2c_xfer_bsc_data(dev, tmp_buf,
>>>                                                       bytes_to_xfer, pmsg);
>>> @@ -512,6 +525,8 @@ static int brcmstb_i2c_xfer(struct i2c_adapter *adapter,
>>> 
>>>                        len -=  bytes_to_xfer;
>>>                        tmp_buf += bytes_to_xfer;
>>> +
>>> +                       cond_per_msg = COND_NOSTART | COND_NOSTOP;
>>>                }
>>>        }
>>> 
>>> --
>>> 2.9.2
>>> 
>> 
>> Thanks
>> Kamal
>> 
> 
> 
> -- 
> Florian