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

[Florian Fainelli <f.fainelli@gmail.com>]

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.
> 
>> 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")

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