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Subject: Re: [PATCH V2] i2c: busses: tegra: Add suspend-resume support
To:     Bitan Biswas <bbiswas@nvidia.com>,
        Laxman Dewangan <ldewangan@nvidia.com>,
        Thierry Reding <treding@nvidia.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        linux-i2c@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org
Cc:     Shardar Mohammed <smohammed@nvidia.com>,
        Sowjanya Komatineni <skomatineni@nvidia.com>,
        Mantravadi Karthik <mkarthik@nvidia.com>
References: <1559800475-5446-1-git-send-email-bbiswas@nvidia.com>
From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <bf93e88f-cbed-3bb0-223a-74ad0b08aa9e@gmail.com>
Date:   Thu, 6 Jun 2019 15:06:48 +0300
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06.06.2019 8:54, Bitan Biswas пишет:
> Post suspend I2C registers have power on reset values. Before any
> transfer initialize I2C registers to prevent I2C transfer timeout
> and implement suspend and resume callbacks needed. Fix below errors
> post suspend:
> 
> 1) Tegra I2C transfer timeout during jetson tx2 resume:
> 
> [   27.520613] pca953x 1-0074: calling pca953x_resume+0x0/0x1b0 @ 2939, parent: i2c-1
> [   27.633623] tegra-i2c 3160000.i2c: i2c transfer timed out
> [   27.639162] pca953x 1-0074: Unable to sync registers 0x3-0x5. -110
> [   27.645336] pca953x 1-0074: Failed to sync GPIO dir registers: -110
> [   27.651596] PM: dpm_run_callback(): pca953x_resume+0x0/0x1b0 returns -110
> [   27.658375] pca953x 1-0074: pca953x_resume+0x0/0x1b0 returned -110 after 127152 usecs
> [   27.666194] PM: Device 1-0074 failed to resume: error -110
> 
> 2) Tegra I2C transfer timeout error on jetson Xavier post resume.
> 
> Remove i2c bus lock-unlock calls in resume callback as i2c_mark_adapter_*
> (suspended-resumed) help ensure i2c core calls from client are not
> executed before i2c-tegra resume.
> 
> Signed-off-by: Bitan Biswas <bbiswas@nvidia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index ebaa78d..76b7926 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1687,7 +1687,30 @@ static int tegra_i2c_remove(struct platform_device *pdev)
>  }
>  
>  #ifdef CONFIG_PM_SLEEP
> +static int tegra_i2c_suspend(struct device *dev)
> +{
> +	struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> +
> +	i2c_mark_adapter_suspended(&i2c_dev->adapter);
> +
> +	return 0;
> +}
> +
> +static int tegra_i2c_resume(struct device *dev)
> +{
> +	struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> +	int ret;
> +
> +	ret = tegra_i2c_init(i2c_dev, false);
> +	if (ret)
> +		return ret;

We're expecting that tegra_i2c_init returns a error code on a failure
and nothing else, hence it will be a bit more expressive to name the
returned variable as "err". There is nothing wrong with yours variant,
this is just a very minor recommendation from me. Please note that a bit
more wise choice of the names makes easier to follow the code for other
people and hence results in a cleaner code.

> +
> +	i2c_mark_adapter_resumed(&i2c_dev->adapter);

Please add a blank line here for a better readability and to make the
patch consistent. You added the blank line in a similar case of
tegra_i2c_suspend() and this makes it inconsistent.

> +	return 0;
> +}
> +
>  static const struct dev_pm_ops tegra_i2c_pm = {
> +	SET_SYSTEM_SLEEP_PM_OPS(tegra_i2c_suspend, tegra_i2c_resume)
>  	SET_RUNTIME_PM_OPS(tegra_i2c_runtime_suspend, tegra_i2c_runtime_resume,
>  			   NULL)
>  };
>