linux-kernel - RE: [PATCH V9 4/5] i2c: tegra: update transfer timeout

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Message-ID: <BYAPR12MB3398D89D631E65C484DC8267C2920@BYAPR12MB3398.namprd12.prod.outlook.com>
Date:   Fri, 1 Feb 2019 19:37:45 +0000
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.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 V9 4/5] i2c: tegra: update transfer timeout


> > BYTES_PER_FIFO_WORD 4
> >  
> >  #define I2C_CNFG				0x000
> > @@ -893,8 +892,9 @@ static int tegra_i2c_issue_bus_clear(struct tegra_i2c_dev *i2c_dev)
> >  		i2c_writel(i2c_dev, reg, I2C_BUS_CLEAR_CNFG);
> >  		tegra_i2c_unmask_irq(i2c_dev, I2C_INT_BUS_CLR_DONE);
> >  
> > -		time_left = wait_for_completion_timeout(&i2c_dev->msg_complete,
> > -							TEGRA_I2C_TIMEOUT);
> > +		time_left = wait_for_completion_timeout(
> > +						&i2c_dev->msg_complete,
> > +						msecs_to_jiffies(1000));
>
> So potentially tegra_i2c_xfer_msg() could take more than 1 second and then fail with -EAGAIN, correct? In that case we should set adapter.timeout in probe to a larger value:
>
Bus clear pulse threshold we are setting is 9 (default as per spec) so bus clear should happen after finishing sending of 9 pulses.
So 1sec is very long time for bus to get released and in case of ARB LOST whole transfer to return EAGAIN will be much less then 1sec

>   i2c_dev->adapter.timeout = 3 * HZ;
>
>
> Otherwise looks good to me:
>
> Reviewed-by: Dmitry Osipenko <digetx@...il.com>