linux-kernel - Re: [PATCH 08/12] i2c: qup: change completion timeout according to transfer length

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Date:   Mon, 19 Feb 2018 16:26:18 +0530
From:   Abhishek Sahu <absahu@...eaurora.org>
To:     Sricharan R <sricharan@...eaurora.org>
Cc:     Andy Gross <andy.gross@...aro.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        David Brown <david.brown@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/12] i2c: qup: change completion timeout according to
 transfer length

On 2018-02-16 10:18, Sricharan R wrote:
> On 2/3/2018 1:28 PM, Abhishek Sahu wrote:
>> Currently the completion timeout is being taken according to
>> maximum transfer length which is too high if SCL is operating in
>> high frequency. This patch calculates timeout on the basis of
>> one-byte transfer time and uses the same for completion timeout.
>> 
>> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
>> ---
>>  drivers/i2c/busses/i2c-qup.c | 9 ++++++---
>>  1 file changed, 6 insertions(+), 3 deletions(-)
>> 
>> diff --git a/drivers/i2c/busses/i2c-qup.c 
>> b/drivers/i2c/busses/i2c-qup.c
>> index a91fc70..6df65ea 100644
>> --- a/drivers/i2c/busses/i2c-qup.c
>> +++ b/drivers/i2c/busses/i2c-qup.c
>> @@ -130,8 +130,8 @@
>>  #define MX_TX_RX_LEN			SZ_64K
>>  #define MX_BLOCKS			(MX_TX_RX_LEN / QUP_READ_LIMIT)
>> 
>> -/* Max timeout in ms for 32k bytes */
>> -#define TOUT_MAX			300
>> +/* Min timeout for i2c transfers */
>> +#define TOUT_MIN			2
>> 
> 
>  may be you can mention, why is this 2 ?
> 

  This 2 seconds is timeout which I am adding on the top of maximum
  xfer time calculated from bus speed to compensate the interrupt
  latency and other factors. It will make xfer timeout minimum as
  2 seconds.

  I will update the comment to explain it in more detail.

  Thanks,
  Abhishek