Re: [PATCH 2/5] i2c: tegra: Restore pinmux on system resume

[Dmitry Osipenko <digetx@gmail.com>]

06.05.2020 22:33, Thierry Reding пишет:
> From: Thierry Reding <treding@nvidia.com>
> 
> Depending on the board design, the I2C controllers found on Tegra SoCs
> may require pinmuxing in order to function. This is done as part of the
> driver's runtime suspend/resume operations. However, the PM core does
> not allow devices to go into runtime suspend during system sleep to
> avoid potential races with the suspend/resume of their parents.
> 
> As a result of this, when Tegra SoCs resume from system suspend, their
> I2C controllers may have lost the pinmux state in hardware, whereas the
> pinctrl subsystem is not aware of this. To fix this, make sure that if
> the I2C controller is not runtime suspended, the runtime suspend code is
> still executed in order to disable the module clock (which we don't need
> to be enabled during sleep) and set the pinmux to the idle state.
> 
> Conversely, make sure that the I2C controller is properly resumed when
> waking up from sleep so that pinmux settings are properly restored.
> 
> This fixes a bug seen with DDC transactions to an HDMI monitor timing
> out when resuming from system suspend.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 7c88611c732c..db142d897604 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1769,10 +1769,14 @@ static int tegra_i2c_remove(struct platform_device *pdev)
>  static int __maybe_unused tegra_i2c_suspend(struct device *dev)
>  {
>  	struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev);
> +	int err = 0;
>  
>  	i2c_mark_adapter_suspended(&i2c_dev->adapter);
>  
> -	return 0;
> +	if (!pm_runtime_status_suspended(dev))
> +		err = tegra_i2c_runtime_suspend(dev);
> +
> +	return err;
>  }
>  
>  static int __maybe_unused tegra_i2c_resume(struct device *dev)
> @@ -1788,9 +1792,11 @@ static int __maybe_unused tegra_i2c_resume(struct device *dev)
>  	if (err)
>  		return err;
>  
> -	err = tegra_i2c_runtime_suspend(dev);
> -	if (err)
> -		return err;
> +	if (pm_runtime_status_suspended(dev)) {
> +		err = tegra_i2c_runtime_suspend(dev);
> +		if (err)
> +			return err;
> +	}
>  
>  	i2c_mark_adapter_resumed(&i2c_dev->adapter);
>  
> 

Is it legal to touch DPAUX registers while DPAUX is in a suspended state?