[PATCH v2 11/11] HID: spi-hid: add panel follower support

[Jingyuan Liang <jingyliang@chromium.org>]

Add support to spi-hid to be a panel follower.

Signed-off-by: Jingyuan Liang <jingyliang@chromium.org>
---
 drivers/hid/spi-hid/spi-hid-core.c | 199 +++++++++++++++++++++++++++++--------
 drivers/hid/spi-hid/spi-hid-core.h |   7 ++
 2 files changed, 163 insertions(+), 43 deletions(-)

diff --git a/drivers/hid/spi-hid/spi-hid-core.c b/drivers/hid/spi-hid/spi-hid-core.c
index ac46e2c7c8aa..6037496ad8a8 100644
--- a/drivers/hid/spi-hid/spi-hid-core.c
+++ b/drivers/hid/spi-hid/spi-hid-core.c
@@ -238,21 +238,21 @@ static const char *spi_hid_power_mode_string(enum hidspi_power_state power_state
 	}
 }
 
-static void spi_hid_suspend(struct spi_hid *shid)
+static int spi_hid_suspend(struct spi_hid *shid)
 {
 	int error;
 	struct device *dev = &shid->spi->dev;
 
 	guard(mutex)(&shid->power_lock);
 	if (shid->power_state == HIDSPI_OFF)
-		return;
+		return 0;
 
 	if (shid->hid) {
 		error = hid_driver_suspend(shid->hid, PMSG_SUSPEND);
 		if (error) {
 			dev_err(dev, "%s failed to suspend hid driver: %d",
 				__func__, error);
-			return;
+			return error;
 		}
 	}
 
@@ -270,21 +270,22 @@ static void spi_hid_suspend(struct spi_hid *shid)
 			dev_err(dev, "%s: could not power down.", __func__);
 			shid->regulator_error_count++;
 			shid->regulator_last_error = error;
-			return;
+			return error;
 		}
 
 		shid->power_state = HIDSPI_OFF;
 	}
+	return 0;
 }
 
-static void spi_hid_resume(struct spi_hid *shid)
+static int spi_hid_resume(struct spi_hid *shid)
 {
 	int error;
 	struct device *dev = &shid->spi->dev;
 
 	guard(mutex)(&shid->power_lock);
 	if (shid->power_state == HIDSPI_ON)
-		return;
+		return 0;
 
 	enable_irq(shid->spi->irq);
 
@@ -298,7 +299,7 @@ static void spi_hid_resume(struct spi_hid *shid)
 			dev_err(dev, "%s: could not power up.", __func__);
 			shid->regulator_error_count++;
 			shid->regulator_last_error = error;
-			return;
+			return error;
 		}
 		shid->power_state = HIDSPI_ON;
 
@@ -307,10 +308,13 @@ static void spi_hid_resume(struct spi_hid *shid)
 
 	if (shid->hid) {
 		error = hid_driver_reset_resume(shid->hid);
-		if (error)
+		if (error) {
 			dev_err(dev, "%s: failed to reset resume hid driver: %d.",
 				__func__, error);
+			return error;
+		}
 	}
+	return 0;
 }
 
 static void spi_hid_stop_hid(struct spi_hid *shid)
@@ -1177,6 +1181,132 @@ const struct attribute_group *spi_hid_groups[] = {
 };
 EXPORT_SYMBOL_GPL(spi_hid_groups);
 
+/*
+ * At the end of probe we initialize the device:
+ *   0) assert reset, bias the interrupt line
+ *   1) sleep minimal reset delay
+ *   2) request IRQ
+ *   3) power up the device
+ *   4) deassert reset (high)
+ * After this we expect an IRQ with a reset response.
+ */
+static int spi_hid_dev_init(struct spi_hid *shid)
+{
+	struct spi_device *spi = shid->spi;
+	struct device *dev = &spi->dev;
+	int error;
+
+	shid->ops->assert_reset(shid->ops);
+
+	shid->ops->sleep_minimal_reset_delay(shid->ops);
+
+	error = devm_request_threaded_irq(dev, spi->irq, NULL, spi_hid_dev_irq,
+					  IRQF_ONESHOT, dev_name(&spi->dev), shid);
+	if (error) {
+		dev_err(dev, "%s: unable to request threaded IRQ.", __func__);
+		return error;
+	}
+	if (device_may_wakeup(dev)) {
+		error = dev_pm_set_wake_irq(dev, spi->irq);
+		if (error) {
+			dev_err(dev, "%s: failed to set wake IRQ.", __func__);
+			return error;
+		}
+	}
+
+	error = shid->ops->power_up(shid->ops);
+	if (error) {
+		dev_err(dev, "%s: could not power up.", __func__);
+		shid->regulator_error_count++;
+		shid->regulator_last_error = error;
+		return error;
+	}
+
+	shid->ops->deassert_reset(shid->ops);
+
+	return 0;
+}
+
+static void spi_hid_panel_follower_work(struct work_struct *work)
+{
+	struct spi_hid *shid = container_of(work, struct spi_hid,
+					    panel_follower_work);
+	int error;
+
+	if (!shid->desc.hid_version)
+		error = spi_hid_dev_init(shid);
+	else
+		error = spi_hid_resume(shid);
+	if (error)
+		dev_warn(&shid->spi->dev, "Power on failed: %d", error);
+	else
+		WRITE_ONCE(shid->panel_follower_work_finished, true);
+
+	/*
+	 * The work APIs provide a number of memory ordering guarantees
+	 * including one that says that memory writes before schedule_work()
+	 * are always visible to the work function, but they don't appear to
+	 * guarantee that a write that happened in the work is visible after
+	 * cancel_work_sync(). We'll add a write memory barrier here to match
+	 * with spi_hid_panel_unpreparing() to ensure that our write to
+	 * panel_follower_work_finished is visible there.
+	 */
+	smp_wmb();
+}
+
+static int spi_hid_panel_follower_resume(struct drm_panel_follower *follower)
+{
+	struct spi_hid *shid = container_of(follower, struct spi_hid, panel_follower);
+
+	/*
+	 * Powering on a touchscreen can be a slow process. Queue the work to
+	 * the system workqueue so we don't block the panel's power up.
+	 */
+	WRITE_ONCE(shid->panel_follower_work_finished, false);
+	schedule_work(&shid->panel_follower_work);
+
+	return 0;
+}
+
+static int spi_hid_panel_follower_suspend(struct drm_panel_follower *follower)
+{
+	struct spi_hid *shid = container_of(follower, struct spi_hid, panel_follower);
+
+	cancel_work_sync(&shid->panel_follower_work);
+
+	/* Match with shid_core_panel_follower_work() */
+	smp_rmb();
+	if (!READ_ONCE(shid->panel_follower_work_finished))
+		return 0;
+
+	return spi_hid_suspend(shid);
+}
+
+static const struct drm_panel_follower_funcs
+				spi_hid_panel_follower_prepare_funcs = {
+	.panel_prepared = spi_hid_panel_follower_resume,
+	.panel_unpreparing = spi_hid_panel_follower_suspend,
+};
+
+static int spi_hid_register_panel_follower(struct spi_hid *shid)
+{
+	struct device *dev = &shid->spi->dev;
+
+	shid->panel_follower.funcs = &spi_hid_panel_follower_prepare_funcs;
+
+	/*
+	 * If we're not in control of our own power up/power down then we can't
+	 * do the logic to manage wakeups. Give a warning if a user thought
+	 * that was possible then force the capability off.
+	 */
+	if (device_can_wakeup(dev)) {
+		dev_warn(dev, "Can't wakeup if following panel\n");
+		device_set_wakeup_capable(dev, false);
+	}
+
+	return drm_panel_add_follower(dev, &shid->panel_follower);
+}
+
 int spi_hid_core_probe(struct spi_device *spi, struct spihid_ops *ops,
 		       struct spi_hid_conf *conf)
 {
@@ -1196,6 +1326,7 @@ int spi_hid_core_probe(struct spi_device *spi, struct spihid_ops *ops,
 	shid->ops = ops;
 	shid->conf = conf;
 	set_bit(SPI_HID_RESET_PENDING, &shid->flags);
+	shid->is_panel_follower = drm_is_panel_follower(&spi->dev);
 
 	spi_set_drvdata(spi, shid);
 
@@ -1208,6 +1339,7 @@ int spi_hid_core_probe(struct spi_device *spi, struct spihid_ops *ops,
 	init_completion(&shid->output_done);
 
 	INIT_WORK(&shid->reset_work, spi_hid_reset_work);
+	INIT_WORK(&shid->panel_follower_work, spi_hid_panel_follower_work);
 
 	/*
 	 * We need to allocate the buffer without knowing the maximum
@@ -1218,42 +1350,18 @@ int spi_hid_core_probe(struct spi_device *spi, struct spihid_ops *ops,
 	if (error)
 		return error;
 
-	/*
-	 * At the end of probe we initialize the device:
-	 *   0) assert reset, bias the interrupt line
-	 *   1) sleep minimal reset delay
-	 *   2) request IRQ
-	 *   3) power up the device
-	 *   4) deassert reset (high)
-	 * After this we expect an IRQ with a reset response.
-	 */
-
-	shid->ops->assert_reset(shid->ops);
-
-	shid->ops->sleep_minimal_reset_delay(shid->ops);
-
-	error = devm_request_threaded_irq(dev, spi->irq, NULL, spi_hid_dev_irq,
-					  IRQF_ONESHOT, dev_name(&spi->dev), shid);
-	if (error) {
-		dev_err(dev, "%s: unable to request threaded IRQ.", __func__);
-		return error;
-	}
-	if (device_may_wakeup(dev)) {
-		error = dev_pm_set_wake_irq(dev, spi->irq);
+	if (shid->is_panel_follower) {
+		error = spi_hid_register_panel_follower(shid);
 		if (error) {
-			dev_err(dev, "%s: failed to set wake IRQ.", __func__);
+			dev_err(dev, "%s: could not add panel follower.", __func__);
 			return error;
 		}
+	} else {
+		error = spi_hid_dev_init(shid);
+		if (error)
+			return error;
 	}
 
-	error = shid->ops->power_up(shid->ops);
-	if (error) {
-		dev_err(dev, "%s: could not power up.", __func__);
-		return error;
-	}
-
-	shid->ops->deassert_reset(shid->ops);
-
 	dev_dbg(dev, "%s: d3 -> %s.", __func__,
 		spi_hid_power_mode_string(shid->power_state));
 
@@ -1267,6 +1375,9 @@ void spi_hid_core_remove(struct spi_device *spi)
 	struct device *dev = &spi->dev;
 	int error;
 
+	if (shid->is_panel_follower)
+		drm_panel_remove_follower(&shid->panel_follower);
+
 	spi_hid_stop_hid(shid);
 
 	shid->ops->assert_reset(shid->ops);
@@ -1280,18 +1391,20 @@ static int spi_hid_core_pm_suspend(struct device *dev)
 {
 	struct spi_hid *shid = dev_get_drvdata(dev);
 
-	spi_hid_suspend(shid);
+	if (shid->is_panel_follower)
+		return 0;
 
-	return 0;
+	return spi_hid_suspend(shid);
 }
 
 static int spi_hid_core_pm_resume(struct device *dev)
 {
 	struct spi_hid *shid = dev_get_drvdata(dev);
 
-	spi_hid_resume(shid);
+	if (shid->is_panel_follower)
+		return 0;
 
-	return 0;
+	return spi_hid_resume(shid);
 }
 
 const struct dev_pm_ops spi_hid_core_pm = {
diff --git a/drivers/hid/spi-hid/spi-hid-core.h b/drivers/hid/spi-hid/spi-hid-core.h
index 61b35a4a4180..72792304c69b 100644
--- a/drivers/hid/spi-hid/spi-hid-core.h
+++ b/drivers/hid/spi-hid/spi-hid-core.h
@@ -7,6 +7,8 @@
 #include <linux/hid-over-spi.h>
 #include <linux/spi/spi.h>
 
+#include <drm/drm_panel.h>
+
 /* Protocol message size constants */
 #define SPI_HID_READ_APPROVAL_LEN		5
 #define SPI_HID_OUTPUT_HEADER_LEN		8
@@ -53,6 +55,10 @@ struct spi_hid {
 	struct spi_hid_input_buf *input;	/* Input buffer. */
 	struct spi_hid_input_buf *response;	/* Response buffer. */
 
+	struct drm_panel_follower panel_follower;
+	bool	is_panel_follower;
+	bool	panel_follower_work_finished;
+
 	u16 response_length;
 	u16 bufsize;
 
@@ -63,6 +69,7 @@ struct spi_hid {
 	unsigned long flags;	/* device flags. */
 
 	struct work_struct reset_work;
+	struct work_struct panel_follower_work;
 
 	/* Control lock to ensure complete output transaction. */
 	struct mutex output_lock;

-- 
2.53.0.983.g0bb29b3bc5-goog