linux-kernel - Re: [PATCH V13 3/5] i2c: tegra: Add DMA support

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Date:   Wed, 6 Feb 2019 19:41:20 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mantravadi Karthik <mkarthik@...dia.com>,
        Shardar Mohammed <smohammed@...dia.com>,
        Timo Alho <talho@...dia.com>
Cc:     "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH V13 3/5] i2c: tegra: Add DMA support

06.02.2019 19:38, Sowjanya Komatineni пишет:
>>>> Looking into timestamps and transactions, DMA timeouts after start of DMA for I2C1 to touch during this transaction.
>>>> While it is waiting for I2C1 DMA transfer, lots of DVC transactions 
>>>> happened thru DMA which are successful
>>>>
>>>> What is the I2C1 speed?
>>>
>>> 400KHz
>>>
>>>> Also incase if device is running slow for some reason, probably timeout was not enough as this patch series changes timeout with base 100mS + msg transfer time based on transfer size.
>>>> Can you give quick try with increased timeout incase if device is running slow?
>>>>
>>>
>>> Tried to increase the timeout to 1 second, doesn't help.
>>>
>>> What helped again is the I2C HW resetting after each transfer. Likely that means that HW isn't programmed correctly, please carefully check every bit.
>>>
>>> DMA-only + I2C HW reset: http://dpaste.com/26AQXFM.txt
>>
>> Seems I found what's the problem. Here is the fix, please include it to v14 if it is correct.
>>
>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c index a9391c3646b6..5ad54da70304 100644
>> --- a/drivers/i2c/busses/i2c-tegra.c
>> +++ b/drivers/i2c/busses/i2c-tegra.c
>> @@ -912,7 +912,7 @@ static irqreturn_t tegra_i2c_isr(int irq, void *dev_id)  static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
>>                                        size_t len)  {
>> -       u32 val, reg;
>> +       u32 val = 0, reg;
>>         u8 dma_burst = 0;
>>         struct dma_slave_config slv_config = {0};
>>         struct dma_chan *chan;
>> @@ -922,7 +922,6 @@ static void tegra_i2c_config_fifo_trig(struct tegra_i2c_dev *i2c_dev,
>>                 reg = I2C_MST_FIFO_CONTROL;
>>         else
>>                 reg = I2C_FIFO_CONTROL;
>> -       val = i2c_readl(i2c_dev, reg);
>  >
>  >        if (i2c_dev->is_curr_dma_xfer) {
>  >                if (len & 0xF)
> 
> Thanks dmitry. Good catch. Didn't caught to my eyes. Yes FIFO_CONTROL is set based on read value without masking and oring causing back-back DMA transfers resulting in incorrect trig levels
> We can directly set trig levels.
> Will fix it.
> 

Awesome!