reset: simple: Add reset callback

The reset-simple code lacks a reset callback that is still pretty easy to
implement. The only real thing to consider is the delay needed for a device
to be reset, so let's expose that as part of the reset-simple driver data.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/reset/reset-simple.c

@@ -11,6 +11,7 @@
  * Maxime Ripard <maxime.ripard@free-electrons.com>
  */
 
+#include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/io.h>
@@ -63,6 +64,24 @@ static int reset_simple_deassert(struct reset_controller_dev *rcdev,
 	return reset_simple_update(rcdev, id, false);
 }
 
+static int reset_simple_reset(struct reset_controller_dev *rcdev,
+			      unsigned long id)
+{
+	struct reset_simple_data *data = to_reset_simple_data(rcdev);
+	int ret;
+
+	if (!data->reset_us)
+		return -ENOTSUPP;
+
+	ret = reset_simple_assert(rcdev, id);
+	if (ret)
+		return ret;
+
+	usleep_range(data->reset_us, data->reset_us * 2);
+
+	return reset_simple_deassert(rcdev, id);
+}
+
 static int reset_simple_status(struct reset_controller_dev *rcdev,
 			       unsigned long id)
 {
@@ -80,6 +99,7 @@ static int reset_simple_status(struct reset_controller_dev *rcdev,
 const struct reset_control_ops reset_simple_ops = {
 	.assert		= reset_simple_assert,
 	.deassert	= reset_simple_deassert,
+	.reset		= reset_simple_reset,
 	.status		= reset_simple_status,
 };
 EXPORT_SYMBOL_GPL(reset_simple_ops);

include/linux/reset/reset-simple.h

@@ -27,13 +27,20 @@
  * @status_active_low: if true, bits read back as cleared while the reset is
  *                     asserted. Otherwise, bits read back as set while the
  *                     reset is asserted.
+ * @reset_us: Minimum delay in microseconds needed that needs to be
+ *            waited for between an assert and a deassert to reset the
+ *            device. If multiple consumers with different delay
+ *            requirements are connected to this controller, it must
+ *            be the largest minimum delay. 0 means that such a delay is
+ *            unknown and the reset operation is unsupported.
  */
 struct reset_simple_data {
 	spinlock_t			lock;
 	void __iomem			*membase;
 	struct reset_controller_dev	rcdev;
 	bool				active_low;
 	bool				status_active_low;
+	unsigned int			reset_us;
 };
 
 extern const struct reset_control_ops reset_simple_ops;