[RFC PATCH 3/4] CHROMIUM: drm: bridge: Generic GPIO mux driver

[Nicolas Boichat]

This driver supports single input, 2 output display mux (e.g.
HDMI mux), that provides its status via a GPIO.

Signed-off-by: Nicolas Boichat <drinkcat@xxxxxxxxxxxx>
---
 drivers/gpu/drm/bridge/Kconfig            |  11 +
 drivers/gpu/drm/bridge/Makefile           |   1 +
 drivers/gpu/drm/bridge/generic-gpio-mux.c | 347 ++++++++++++++++++++++++++++++
 3 files changed, 359 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/generic-gpio-mux.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index da489f0..f1f6fc6 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -41,6 +41,17 @@ config DRM_DW_HDMI_AHB_AUDIO
 	  Designware HDMI block.  This is used in conjunction with
 	  the i.MX6 HDMI driver.
 
+config DRM_GENERIC_GPIO_MUX
+	tristate "Generic GPIO-controlled mux"
+	depends on DRM
+	depends on OF
+	select DRM_KMS_HELPER
+	---help---
+	  This bridge driver models a GPIO-controlled display mux with one
+	  input, 2 outputs (e.g. an HDMI mux). The hardware decides which output
+	  is active, reports it as a GPIO, and the driver redirects calls to the
+	  appropriate downstream bridge (if any).
+
 config DRM_NXP_PTN3460
 	tristate "NXP PTN3460 DP/LVDS bridge"
 	depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 4846465..cb97274fd 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -4,6 +4,7 @@ obj-$(CONFIG_DRM_ANALOGIX_ANX7688) += analogix-anx7688.o
 obj-$(CONFIG_DRM_ANALOGIX_ANX78XX) += analogix-anx78xx.o
 obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
 obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
+obj-$(CONFIG_DRM_GENERIC_GPIO_MUX) += generic-gpio-mux.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
 obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
 obj-$(CONFIG_DRM_SII902X) += sii902x.o
diff --git a/drivers/gpu/drm/bridge/generic-gpio-mux.c b/drivers/gpu/drm/bridge/generic-gpio-mux.c
new file mode 100644
index 0000000..d3367e2
--- /dev/null
+++ b/drivers/gpu/drm/bridge/generic-gpio-mux.c
@@ -0,0 +1,347 @@
+/*
+ * ANX7688 HDMI->DP bridge driver
+ *
+ * Copyright (C) 2016 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/gpio.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <linux/of_graph.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_crtc_helper.h>
+
+struct gpio_display_mux {
+	struct device *dev;
+
+	struct gpio_desc *gpiod_detect;
+	int detect_irq;
+
+	struct drm_bridge bridge;
+
+	struct drm_bridge *next[2];
+
+	struct mutex lock;
+	int active;
+	bool enabled;
+};
+
+static inline struct gpio_display_mux *bridge_to_gpio_display_mux(
+		struct drm_bridge *bridge)
+{
+	return container_of(bridge, struct gpio_display_mux, bridge);
+}
+
+static irqreturn_t gpio_display_mux_det_threaded_handler(int unused, void *data)
+{
+	struct gpio_display_mux *gpio_display_mux = data;
+	struct drm_bridge *next;
+	int active;
+
+	active = gpiod_get_value(gpio_display_mux->gpiod_detect);
+
+	dev_dbg(gpio_display_mux->dev, "Interrupt %d!\n", active);
+
+	if (active == gpio_display_mux->active)
+		return IRQ_HANDLED;
+
+	/* Disable previous bridge */
+	mutex_lock(&gpio_display_mux->lock);
+	if (gpio_display_mux->enabled) {
+		next = gpio_display_mux->next[gpio_display_mux->active];
+		if (next && next->funcs->disable)
+			next->funcs->disable(next);
+	}
+	mutex_unlock(&gpio_display_mux->lock);
+
+	if (gpio_display_mux->bridge.dev)
+		drm_kms_helper_hotplug_event(gpio_display_mux->bridge.dev);
+
+	/* Enable current bridge */
+	mutex_lock(&gpio_display_mux->lock);
+	if (gpio_display_mux->enabled) {
+		next = gpio_display_mux->next[active];
+		if (next && next->funcs->enable)
+			next->funcs->enable(next);
+	}
+	gpio_display_mux->active = active;
+	mutex_unlock(&gpio_display_mux->lock);
+
+	return IRQ_HANDLED;
+}
+
+static int gpio_display_mux_attach(struct drm_bridge *bridge)
+{
+	struct gpio_display_mux *gpio_display_mux =
+			bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(gpio_display_mux->next); i++) {
+		next = gpio_display_mux->next[i];
+		if (next)
+			next->encoder = bridge->encoder;
+	}
+
+	return 0;
+}
+
+static bool gpio_display_mux_mode_fixup(struct drm_bridge *bridge,
+				const struct drm_display_mode *mode,
+				struct drm_display_mode *adjusted_mode)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+
+	next = gpio_display_mux->next[gpio_display_mux->active];
+
+	if (next && next->funcs->mode_fixup)
+		return next->funcs->mode_fixup(next, mode, adjusted_mode);
+	else
+		return true;
+}
+
+static void gpio_display_mux_mode_set(struct drm_bridge *bridge,
+				struct drm_display_mode *mode,
+				struct drm_display_mode *adjusted_mode)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+
+	next = gpio_display_mux->next[gpio_display_mux->active];
+
+	if (next && next->funcs->mode_set)
+		next->funcs->mode_set(next, mode, adjusted_mode);
+}
+
+static void gpio_display_mux_enable(struct drm_bridge *bridge)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+
+	mutex_lock(&gpio_display_mux->lock);
+
+	next = gpio_display_mux->next[gpio_display_mux->active];
+	if (next && next->funcs->enable)
+		next->funcs->enable(next);
+
+	gpio_display_mux->enabled = true;
+
+	mutex_unlock(&gpio_display_mux->lock);
+}
+
+static void gpio_display_mux_disable(struct drm_bridge *bridge)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+
+	mutex_lock(&gpio_display_mux->lock);
+
+	next = gpio_display_mux->next[gpio_display_mux->active];
+	if (next && next->funcs->disable)
+		next->funcs->disable(next);
+
+	gpio_display_mux->enabled = false;
+
+	mutex_unlock(&gpio_display_mux->lock);
+}
+
+/**
+ * Since this driver _reacts_ to mux changes, we need to make sure all
+ * downstream bridges are pre-enabled.
+ */
+static void gpio_display_mux_pre_enable(struct drm_bridge *bridge)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(gpio_display_mux->next); i++) {
+		next = gpio_display_mux->next[i];
+		if (next && next->funcs->pre_enable)
+			next->funcs->pre_enable(next);
+	}
+}
+
+static void gpio_display_mux_post_disable(struct drm_bridge *bridge)
+{
+	struct gpio_display_mux *gpio_display_mux =
+		bridge_to_gpio_display_mux(bridge);
+	struct drm_bridge *next;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(gpio_display_mux->next); i++) {
+		next = gpio_display_mux->next[i];
+		if (next && next->funcs->post_disable)
+			next->funcs->post_disable(next);
+	}
+}
+
+static const struct drm_bridge_funcs gpio_display_mux_bridge_funcs = {
+	.attach = gpio_display_mux_attach,
+	.mode_fixup = gpio_display_mux_mode_fixup,
+	.disable = gpio_display_mux_disable,
+	.post_disable = gpio_display_mux_post_disable,
+	.mode_set = gpio_display_mux_mode_set,
+	.pre_enable = gpio_display_mux_pre_enable,
+	.enable = gpio_display_mux_enable,
+};
+
+static int gpio_display_mux_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct gpio_display_mux *gpio_display_mux;
+	struct device_node *port, *ep, *remote;
+	int ret;
+	u32 reg;
+
+	gpio_display_mux = devm_kzalloc(dev, sizeof(*gpio_display_mux),
+					GFP_KERNEL);
+	if (!gpio_display_mux)
+		return -ENOMEM;
+
+	mutex_init(&gpio_display_mux->lock);
+
+	platform_set_drvdata(pdev, gpio_display_mux);
+	gpio_display_mux->dev = &pdev->dev;
+
+	gpio_display_mux->bridge.of_node = dev->of_node;
+
+	gpio_display_mux->gpiod_detect =
+		devm_gpiod_get(dev, "detect", GPIOD_IN);
+	if (IS_ERR(gpio_display_mux->gpiod_detect))
+		return PTR_ERR(gpio_display_mux->gpiod_detect);
+
+	gpio_display_mux->detect_irq =
+		gpiod_to_irq(gpio_display_mux->gpiod_detect);
+	if (gpio_display_mux->detect_irq < 0) {
+		dev_err(dev, "Failed to get output irq %d\n",
+			gpio_display_mux->detect_irq);
+		return -ENODEV;
+	}
+
+	port = of_graph_get_port_by_id(dev->of_node, 1);
+	if (!port) {
+		dev_err(dev, "Missing output port node\n");
+		return -EINVAL;
+	}
+
+	for_each_child_of_node(port, ep) {
+		if (!ep->name || (of_node_cmp(ep->name, "endpoint") != 0)) {
+			of_node_put(ep);
+			continue;
+		}
+
+		if (of_property_read_u32(ep, "reg", &reg) < 0 ||
+				reg >= ARRAY_SIZE(gpio_display_mux->next)) {
+			dev_err(dev,
+			    "Missing/invalid reg property for endpoint %s\n",
+				ep->full_name);
+			of_node_put(ep);
+			of_node_put(port);
+			return -EINVAL;
+		}
+
+		remote = of_graph_get_remote_port_parent(ep);
+		if (!remote) {
+			dev_err(dev,
+			    "Missing connector/bridge node for endpoint %s\n",
+				ep->full_name);
+			of_node_put(ep);
+			of_node_put(port);
+			return -EINVAL;
+		}
+		of_node_put(ep);
+
+		if (of_device_is_compatible(remote, "hdmi-connector")) {
+			of_node_put(remote);
+			continue;
+		}
+
+		gpio_display_mux->next[reg] = of_drm_find_bridge(remote);
+		if (!gpio_display_mux->next[reg]) {
+			dev_err(dev, "Waiting for external bridge %s\n",
+				remote->name);
+			of_node_put(remote);
+			of_node_put(port);
+			return -EPROBE_DEFER;
+		}
+
+		of_node_put(remote);
+	}
+	of_node_put(port);
+
+	gpio_display_mux->bridge.funcs = &gpio_display_mux_bridge_funcs;
+	ret = drm_bridge_add(&gpio_display_mux->bridge);
+	if (ret < 0) {
+		dev_err(dev, "Failed to add drm bridge\n");
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(dev, gpio_display_mux->detect_irq,
+				NULL,
+				gpio_display_mux_det_threaded_handler,
+				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING |
+					IRQF_ONESHOT,
+				"gpio-display-mux-det", gpio_display_mux);
+	if (ret) {
+		dev_err(dev, "Failed to request MUX_DET threaded irq\n");
+		goto err_bridge_remove;
+	}
+
+	gpio_display_mux->active =
+			gpiod_get_value(gpio_display_mux->gpiod_detect);
+
+	return 0;
+
+err_bridge_remove:
+	drm_bridge_remove(&gpio_display_mux->bridge);
+
+	return ret;
+}
+
+static int gpio_display_mux_remove(struct platform_device *pdev)
+{
+	struct gpio_display_mux *gpio_display_mux = platform_get_drvdata(pdev);
+
+	drm_bridge_remove(&gpio_display_mux->bridge);
+
+	return 0;
+}
+
+static const struct of_device_id gpio_display_mux_match[] = {
+	{ .compatible = "gpio-display-mux", },
+	{},
+};
+
+struct platform_driver gpio_display_mux_driver = {
+	.probe = gpio_display_mux_probe,
+	.remove = gpio_display_mux_remove,
+	.driver = {
+		.name = "gpio-display-mux",
+		.of_match_table = gpio_display_mux_match,
+	},
+};
+
+module_platform_driver(gpio_display_mux_driver);
+
+MODULE_DESCRIPTION("GPIO-controlled display mux");
+MODULE_AUTHOR("Nicolas Boichat <drinkcat@xxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
-- 
2.8.0.rc3.226.g39d4020