linux-kernel - Re: [PATCH] i2c: stm32: Fixes multibyte transfer for STM32F4 I2C controller

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Message-ID: <CAFvLkMTsgxpjoGRgq7J0NFkT=YsOTYL6smkVhOPcfD=26Hzutg@mail.gmail.com>
Date:   Tue, 24 Oct 2017 13:45:43 +0200
From:   Radosław Pietrzyk <radoslaw.pietrzyk@...il.com>
To:     Pierre Yves MORDRET <pierre-yves.mordret@...com>
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        "open list:I2C SUBSYSTEM" <linux-i2c@...r.kernel.org>,
        "moderated list:ARM/STM32 ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: stm32: Fixes multibyte transfer for STM32F4 I2C controller

I'm afraid that didn't help and the problem still exists even with
those patches applied.

2017-10-17 16:35 GMT+02:00 Pierre Yves MORDRET <pierre-yves.mordret@...com>:
>
>
> On 10/17/2017 03:51 PM, Radosław Pietrzyk wrote:
>> I can try of course but it means that any IRQ delay may cause the same
>> problem so the question is whether the driver should be vulnerable to
>> such use cases.
>>
>
> I may or ... may or not. If those patches don't find effectiveness at your side
> I will have to look at it closer.
> Nonetheless I prefer to start from something more stable in term of clock before
> investigating further.
>
> Please let me know
>
> Regards
>> 2017-10-17 15:18 GMT+02:00 Pierre Yves MORDRET <pierre-yves.mordret@...com>:
>>>
>>>
>>> On 10/12/2017 11:55 AM, Radosław Pietrzyk wrote:
>>>> It looks like there is a use case when IRQ handler is delayed a bit
>>>> and the logic in the driver does not work. What is the real root cause
>>>> I don't know.
>>>>
>>>
>>> As far as I know on this STM32 F4 platform there is some trouble with timer
>>> events that may have bad influences on scheduling. Some tasks could be delayed
>>> for some reasons.
>>> It would be great if the following patches below could help in your matter
>>> https://patchwork.kernel.org/patch/9980961/
>>> https://patchwork.kernel.org/patch/9980963/
>>> https://patchwork.kernel.org/patch/9980965/
>>> https://patchwork.kernel.org/patch/9980967/
>>>
>>> Would you mind to test those ?
>>> Thanks
>>>
>>>> 2017-10-12 11:31 GMT+02:00 Pierre Yves MORDRET <pierre-yves.mordret@...com>:
>>>>>
>>>>>
>>>>> On 10/11/2017 01:53 PM, Radoslaw Pietrzyk wrote:
>>>>>>       Do not read data on RXNE but on BTF only due to HW
>>>>>>       synchronisation problems and NACKing read data too early.
>>>>>>       It was found during testing of stmpe811 touchscreen driver.
>>>>>>
>>>>>
>>>>> Would you mind to explain what is behind "hw sync issue" you've seen ?
>>>>>
>>>>>> Signed-off-by: Radoslaw Pietrzyk <radoslaw.pietrzyk@...il.com>
>>>>>> ---
>>>>>>  drivers/i2c/busses/i2c-stm32f4.c | 11 +----------
>>>>>>  1 file changed, 1 insertion(+), 10 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c
>>>>>> index 4ec1084..86bcf4c 100644
>>>>>> --- a/drivers/i2c/busses/i2c-stm32f4.c
>>>>>> +++ b/drivers/i2c/busses/i2c-stm32f4.c
>>>>>> @@ -409,16 +409,9 @@ static void stm32f4_i2c_handle_read(struct stm32f4_i2c_dev *i2c_dev)
>>>>>>        * So, here we just disable buffer interrupt in order to avoid another
>>>>>>        * system preemption due to RX not empty event.
>>>>>>        */
>>>>>> -     case 2:
>>>>>> -     case 3:
>>>>>> +     default:
>>>>>>               stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
>>>>>>               break;
>>>>>> -     /*
>>>>>> -      * For N byte reception with N > 3 we directly read data register
>>>>>> -      * until N-2 data.
>>>>>> -      */
>>>>>> -     default:
>>>>>> -             stm32f4_i2c_read_msg(i2c_dev);
>>>>>>       }
>>>>>>  }
>>>>>>
>>>>>> @@ -470,8 +463,6 @@ static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
>>>>>>                */
>>>>>>               reg = i2c_dev->base + STM32F4_I2C_CR1;
>>>>>>               stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK);
>>>>>> -             stm32f4_i2c_read_msg(i2c_dev);
>>>>>> -             break;
>>>>>>       default:
>>>>>>               stm32f4_i2c_read_msg(i2c_dev);
>>>>>>       }
>>>>>>