06.05.2020 22:33, Thierry Reding пишет:
> From: Thierry Reding <treding@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
> 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?
