[PATCH V3] i2c: busses: tegra: Add suspend-resume support

[Bitan Biswas]

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@xxxxxxxxxx>
---
 drivers/i2c/busses/i2c-tegra.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index ebaa78d..1dbba39 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1687,7 +1687,31 @@ 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 err;
+
+	err = tegra_i2c_init(i2c_dev, false);
+	if (err)
+		return err;
+
+	i2c_mark_adapter_resumed(&i2c_dev->adapter);
+
+	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)
 };
-- 
2.7.4