i2c: riic: Add suspend/resume support

Add suspend/resume support for the RIIC driver. This is necessary for the
Renesas RZ/G3S SoC which support suspend to deep sleep state where power
to most of the SoC components is turned off. As a result the I2C controller
needs to be reconfigured after suspend/resume. For this, the reset line
was stored in the driver private data structure as well as i2c timings.
The reset line and I2C timings are necessary to re-initialize the
controller after resume.

Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>

drivers/i2c/busses/i2c-riic.c

@@ -105,6 +105,8 @@ struct riic_dev {
 	struct completion msg_done;
 	struct i2c_adapter adapter;
 	struct clk *clk;
+	struct reset_control *rstc;
+	struct i2c_timings i2c_t;
 };
 
 struct riic_irq_desc {
@@ -302,11 +304,12 @@ static const struct i2c_algorithm riic_algo = {
 	.functionality = riic_func,
 };
 
-static int riic_init_hw(struct riic_dev *riic, struct i2c_timings *t)
+static int riic_init_hw(struct riic_dev *riic)
 {
 	int ret;
 	unsigned long rate;
 	int total_ticks, cks, brl, brh;
+	struct i2c_timings *t = &riic->i2c_t;
 	struct device *dev = riic->adapter.dev.parent;
 
 	if (t->bus_freq_hz > I2C_MAX_FAST_MODE_FREQ) {
@@ -423,8 +426,6 @@ static int riic_i2c_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct riic_dev *riic;
 	struct i2c_adapter *adap;
-	struct i2c_timings i2c_t;
-	struct reset_control *rstc;
 	int i, ret;
 
 	riic = devm_kzalloc(dev, sizeof(*riic), GFP_KERNEL);
@@ -441,16 +442,16 @@ static int riic_i2c_probe(struct platform_device *pdev)
 		return PTR_ERR(riic->clk);
 	}
 
-	rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
-	if (IS_ERR(rstc))
-		return dev_err_probe(dev, PTR_ERR(rstc),
+	riic->rstc = devm_reset_control_get_optional_exclusive(dev, NULL);
+	if (IS_ERR(riic->rstc))
+		return dev_err_probe(dev, PTR_ERR(riic->rstc),
 				     "Error: missing reset ctrl\n");
 
-	ret = reset_control_deassert(rstc);
+	ret = reset_control_deassert(riic->rstc);
 	if (ret)
 		return ret;
 
-	ret = devm_add_action_or_reset(dev, riic_reset_control_assert, rstc);
+	ret = devm_add_action_or_reset(dev, riic_reset_control_assert, riic->rstc);
 	if (ret)
 		return ret;
 
@@ -479,14 +480,14 @@ static int riic_i2c_probe(struct platform_device *pdev)
 
 	init_completion(&riic->msg_done);
 
-	i2c_parse_fw_timings(dev, &i2c_t, true);
+	i2c_parse_fw_timings(dev, &riic->i2c_t, true);
 
 	/* Default 0 to save power. Can be overridden via sysfs for lower latency. */
 	pm_runtime_set_autosuspend_delay(dev, 0);
 	pm_runtime_use_autosuspend(dev);
 	pm_runtime_enable(dev);
 
-	ret = riic_init_hw(riic, &i2c_t);
+	ret = riic_init_hw(riic);
 	if (ret)
 		goto out;
 
@@ -496,7 +497,7 @@ static int riic_i2c_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, riic);
 
-	dev_info(dev, "registered with %dHz bus speed\n", i2c_t.bus_freq_hz);
+	dev_info(dev, "registered with %dHz bus speed\n", riic->i2c_t.bus_freq_hz);
 	return 0;
 
 out:
@@ -553,6 +554,55 @@ static const struct riic_of_data riic_rz_v2h_info = {
 	},
 };
 
+static int riic_i2c_suspend(struct device *dev)
+{
+	struct riic_dev *riic = dev_get_drvdata(dev);
+	int ret;
+
+	ret = pm_runtime_resume_and_get(dev);
+	if (ret)
+		return ret;
+
+	i2c_mark_adapter_suspended(&riic->adapter);
+
+	/* Disable output on SDA, SCL pins. */
+	riic_clear_set_bit(riic, ICCR1_ICE, 0, RIIC_ICCR1);
+
+	pm_runtime_mark_last_busy(dev);
+	pm_runtime_put_sync(dev);
+
+	return reset_control_assert(riic->rstc);
+}
+
+static int riic_i2c_resume(struct device *dev)
+{
+	struct riic_dev *riic = dev_get_drvdata(dev);
+	int ret;
+
+	ret = reset_control_deassert(riic->rstc);
+	if (ret)
+		return ret;
+
+	ret = riic_init_hw(riic);
+	if (ret) {
+		/*
+		 * In case this happens there is no way to recover from this
+		 * state. The driver will remain loaded. We want to avoid
+		 * keeping the reset line de-asserted for no reason.
+		 */
+		reset_control_assert(riic->rstc);
+		return ret;
+	}
+
+	i2c_mark_adapter_resumed(&riic->adapter);
+
+	return 0;
+}
+
+static const struct dev_pm_ops riic_i2c_pm_ops = {
+	SYSTEM_SLEEP_PM_OPS(riic_i2c_suspend, riic_i2c_resume)
+};
+
 static const struct of_device_id riic_i2c_dt_ids[] = {
 	{ .compatible = "renesas,riic-rz", .data = &riic_rz_a_info },
 	{ .compatible = "renesas,riic-r9a09g057", .data = &riic_rz_v2h_info },
@@ -565,6 +615,7 @@ static struct platform_driver riic_i2c_driver = {
 	.driver		= {
 		.name	= "i2c-riic",
 		.of_match_table = riic_i2c_dt_ids,
+		.pm	= pm_ptr(&riic_i2c_pm_ops),
 	},
 };