power: reset: at91-reset: add reset_controller_dev support

SAMA7G5 reset controller has 5 extra lines that goes to different devices
(3 lines to USB PHYs, 1 line to DDR controller, 1 line to DDR PHY
controller). These reset lines could be requested by different controller
drivers (e.g. USB PHY driver) and these controllers' drivers could
assert/deassert these lines when necessary. Thus add support for
reset_controller_dev which brings this functionality.

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/reset/at91-reset.c

@@ -17,6 +17,7 @@
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
+#include <linux/reset-controller.h>
 
 #include <soc/at91/at91sam9_ddrsdr.h>
 #include <soc/at91/at91sam9_sdramc.h>
@@ -65,22 +66,30 @@ enum reset_type {
  * struct at91_reset - AT91 reset specific data structure
  * @rstc_base:		base address for system reset
  * @ramc_base:		array with base addresses of RAM controllers
+ * @dev_base:		base address for devices reset
  * @sclk:		slow clock
  * @data:		platform specific reset data
+ * @rcdev:		reset controller device
+ * @lock:		lock for devices reset register access
  * @nb:			reset notifier block
  * @args:		SoC specific system reset arguments
  * @ramc_lpr:		SDRAM Controller Low Power Register
  */
 struct at91_reset {
 	void __iomem *rstc_base;
 	void __iomem *ramc_base[2];
+	void __iomem *dev_base;
 	struct clk *sclk;
 	const struct at91_reset_data *data;
+	struct reset_controller_dev rcdev;
+	spinlock_t lock;
 	struct notifier_block nb;
 	u32 args;
 	u32 ramc_lpr;
 };
 
+#define to_at91_reset(r)	container_of(r, struct at91_reset, rcdev)
+
 /**
  * struct at91_reset_data - AT91 reset data
  * @reset_args:			SoC specific system reset arguments
@@ -222,6 +231,89 @@ static const struct of_device_id at91_reset_of_match[] = {
 };
 MODULE_DEVICE_TABLE(of, at91_reset_of_match);
 
+static int at91_reset_update(struct reset_controller_dev *rcdev,
+			     unsigned long id, bool assert)
+{
+	struct at91_reset *reset = to_at91_reset(rcdev);
+	unsigned long flags;
+	u32 val;
+
+	spin_lock_irqsave(&reset->lock, flags);
+	val = readl_relaxed(reset->dev_base);
+	if (assert)
+		val |= BIT(id);
+	else
+		val &= ~BIT(id);
+	writel_relaxed(val, reset->dev_base);
+	spin_unlock_irqrestore(&reset->lock, flags);
+
+	return 0;
+}
+
+static int at91_reset_assert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	return at91_reset_update(rcdev, id, true);
+}
+
+static int at91_reset_deassert(struct reset_controller_dev *rcdev,
+			       unsigned long id)
+{
+	return at91_reset_update(rcdev, id, false);
+}
+
+static int at91_reset_dev_status(struct reset_controller_dev *rcdev,
+				 unsigned long id)
+{
+	struct at91_reset *reset = to_at91_reset(rcdev);
+	u32 val;
+
+	val = readl_relaxed(reset->dev_base);
+
+	return !!(val & BIT(id));
+}
+
+static const struct reset_control_ops at91_reset_ops = {
+	.assert = at91_reset_assert,
+	.deassert = at91_reset_deassert,
+	.status = at91_reset_dev_status,
+};
+
+static int at91_reset_of_xlate(struct reset_controller_dev *rcdev,
+			       const struct of_phandle_args *reset_spec)
+{
+	struct at91_reset *reset = to_at91_reset(rcdev);
+
+	if (!reset->data->n_device_reset ||
+	    (reset_spec->args[0] < reset->data->device_reset_min_id ||
+	     reset_spec->args[0] > reset->data->device_reset_max_id))
+		return -EINVAL;
+
+	return reset_spec->args[0];
+}
+
+static int at91_rcdev_init(struct at91_reset *reset,
+			   struct platform_device *pdev)
+{
+	if (!reset->data->n_device_reset)
+		return 0;
+
+	reset->dev_base = devm_of_iomap(&pdev->dev, pdev->dev.of_node, 1,
+					NULL);
+	if (IS_ERR(reset->dev_base))
+		return -ENODEV;
+
+	spin_lock_init(&reset->lock);
+	reset->rcdev.ops = &at91_reset_ops;
+	reset->rcdev.owner = THIS_MODULE;
+	reset->rcdev.of_node = pdev->dev.of_node;
+	reset->rcdev.nr_resets = reset->data->n_device_reset;
+	reset->rcdev.of_reset_n_cells = 1;
+	reset->rcdev.of_xlate = at91_reset_of_xlate;
+
+	return devm_reset_controller_register(&pdev->dev, &reset->rcdev);
+}
+
 static int __init at91_reset_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *match;
@@ -272,6 +364,10 @@ static int __init at91_reset_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, reset);
 
+	ret = at91_rcdev_init(reset, pdev);
+	if (ret)
+		goto disable_clk;
+
 	if (of_device_is_compatible(pdev->dev.of_node, "microchip,sam9x60-rstc")) {
 		u32 val = readl(reset->rstc_base + AT91_RSTC_MR);
 
@@ -280,14 +376,16 @@ static int __init at91_reset_probe(struct platform_device *pdev)
 	}
 
 	ret = register_restart_handler(&reset->nb);
-	if (ret) {
-		clk_disable_unprepare(reset->sclk);
-		return ret;
-	}
+	if (ret)
+		goto disable_clk;
 
 	at91_reset_status(pdev, reset->rstc_base);
 
 	return 0;
+
+disable_clk:
+	clk_disable_unprepare(reset->sclk);
+	return ret;
 }
 
 static int __exit at91_reset_remove(struct platform_device *pdev)