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From: asheplyakov@yandex.ru
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Date: Fri, 20 May 2022 20:28:27 +0400
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Cc: Vitaly Chikunov <vt@altlinux.org>,
 Alexey Sheplyakov <asheplyakov@basealt.ru>, Igor Chudov <nir@basealt.ru>,
 Evgeny Sinelnikov <sin@basealt.ru>, "Vadim V. Vlasov" <vvv19xx@gmail.com>
Subject: [devel] [PATCH 13/35] drm: new bridge driver - stdp4028
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From: "Vadim V. Vlasov" <vvv19xx@gmail.com>

MegaChips stdp4028 is LVDS to DP bridge.

The driver can work in interrupt or poll mode.
Videomodes may be specified in the devicetree or read from EDID.

Signed-off-by: Vadim V. Vlasov <vvv19xx@gmail.com>
Signed-off-by: Alexey Sheplyakov <asheplyakov@basealt.ru>
X-feature-Baikal-M
---
 drivers/gpu/drm/bridge/Kconfig    |   8 +
 drivers/gpu/drm/bridge/Makefile   |   1 +
 drivers/gpu/drm/bridge/stdp4028.c | 486 ++++++++++++++++++++++++++++++
 3 files changed, 495 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/stdp4028.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 44ad70939663..3795e7020aec 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -316,6 +316,14 @@ config DRM_TI_TPD12S015
 	  Texas Instruments TPD12S015 HDMI level shifter and ESD protection
 	  driver.
 
+config DRM_STDP4028
+	tristate "MegaChips STDP4028 DP bridge"
+	depends on OF
+	select DRM_KMS_HELPER
+	select DRM_PANEL
+	help
+	  MegaChips STDP4028 DP bridge driver
+
 source "drivers/gpu/drm/bridge/analogix/Kconfig"
 
 source "drivers/gpu/drm/bridge/adv7511/Kconfig"
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index f2c73683cfcb..9faf98509d2c 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -29,6 +29,7 @@ obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
 obj-$(CONFIG_DRM_TI_TPD12S015) += ti-tpd12s015.o
 obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
 obj-$(CONFIG_DRM_ITE_IT66121) += ite-it66121.o
+obj-$(CONFIG_DRM_STDP4028) += stdp4028.o
 
 obj-y += analogix/
 obj-y += cadence/
diff --git a/drivers/gpu/drm/bridge/stdp4028.c b/drivers/gpu/drm/bridge/stdp4028.c
new file mode 100644
index 000000000000..12b3ff31b213
--- /dev/null
+++ b/drivers/gpu/drm/bridge/stdp4028.c
@@ -0,0 +1,486 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for MegaChips STDP4028 LVDS to DP display bridge
+ */
+
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_gpio.h>
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_edid.h>
+#include <drm/drm_print.h>
+#include <drm/drm_probe_helper.h>
+
+/* video modes */
+#include <video/display_timing.h>
+#include <video/of_display_timing.h>
+#include <video/videomode.h>
+
+#define MAX_PIXEL_CLOCK 330000
+
+#define EDID_EXT_BLOCK_CNT 0x7E
+
+#define STDP4028_PRODUCT_ID_REG 0x00
+#define STDP4028_IRQ_OUT_CONF_REG 0x02
+#define STDP4028_IRQ_STS_REG 0x03
+#define STDP4028_I2C_CTRL_REG 0x08
+#define STDP4028_LVDS_FMT_REG 0x0B
+#define STDP4028_LVDS_CTRL0_REG 0x0C
+#define STDP4028_DPTX_IRQ_EN_REG 0x3C
+#define STDP4028_DPTX_IRQ_STS_REG 0x3D
+#define STDP4028_DPTX_STS_REG 0x3E
+
+#define STDP4028_DPTX_DP_IRQ_EN 0x10
+
+#define STDP4028_DPTX_HOTPLUG_IRQ_EN 0x04
+#define STDP4028_DPTX_LINK_CH_IRQ_EN 0x20
+#define STDP4028_DPTX_IRQ_CONFIG \
+	(STDP4028_DPTX_LINK_CH_IRQ_EN | STDP4028_DPTX_HOTPLUG_IRQ_EN)
+
+#define STDP4028_DPTX_HOTPLUG_STS 0x02
+#define STDP4028_DPTX_LINK_STS 0x10
+#define STDP4028_CON_STATE_CONNECTED \
+	(STDP4028_DPTX_HOTPLUG_STS | STDP4028_DPTX_LINK_STS)
+
+#define STDP4028_DPTX_HOTPLUG_CH_STS 0x04
+#define STDP4028_DPTX_LINK_CH_STS 0x20
+#define STDP4028_DPTX_IRQ_CLEAR \
+	(STDP4028_DPTX_LINK_CH_STS | STDP4028_DPTX_HOTPLUG_CH_STS)
+
+struct stdp4028 {
+	struct drm_connector connector;
+	struct drm_bridge bridge;
+	struct i2c_client *stdp4028_i2c;
+	struct i2c_client *edid_i2c;
+	struct edid *edid;
+	struct gpio_desc *reset_gpio;
+	struct mutex lock;
+	int channels;
+	int chan_cfg;
+};
+
+static inline int stdp_read(struct stdp4028 *stdp, int reg)
+{
+	int ret;
+
+	ret = i2c_smbus_read_word_data(stdp->stdp4028_i2c, reg);
+	if (ret < 0)
+		return ret;
+	return be16_to_cpu(ret);
+}
+
+static inline int stdp_write(struct stdp4028 *stdp, int reg, u16 val)
+{
+	val = cpu_to_be16(val);
+	return i2c_smbus_write_word_data(stdp->stdp4028_i2c, reg, val);
+}
+
+#define bridge_to_stdp4028(bridge) \
+	container_of(bridge, struct stdp4028, bridge)
+
+#define connector_to_stdp4028(connector) \
+	container_of(connector, struct stdp4028, connector)
+
+static u8 *stdp4028_get_edid(struct i2c_client *client)
+{
+	struct i2c_adapter *adapter = client->adapter;
+	unsigned char start = 0x00;
+	unsigned int total_size;
+	u8 *block = kmalloc(EDID_LENGTH, GFP_KERNEL);
+
+	struct i2c_msg msgs[] = {
+		{
+			.addr   = client->addr,
+			.flags  = 0,
+			.len    = 1,
+			.buf    = &start,
+		}, {
+			.addr   = client->addr,
+			.flags  = I2C_M_RD,
+			.len    = EDID_LENGTH,
+			.buf    = block,
+		}
+	};
+
+	if (!block)
+		return NULL;
+
+	if (i2c_transfer(adapter, msgs, 2) != 2) {
+		DRM_ERROR("Unable to read EDID.\n");
+		goto err;
+	}
+
+	if (!drm_edid_block_valid(block, 0, false, NULL)) {
+		DRM_ERROR("Invalid EDID data\n");
+		goto err;
+	}
+
+	total_size = (block[EDID_EXT_BLOCK_CNT] + 1) * EDID_LENGTH;
+	if (total_size > EDID_LENGTH) {
+		kfree(block);
+		block = kmalloc(total_size, GFP_KERNEL);
+		if (!block)
+			return NULL;
+
+		/* Yes, read the entire buffer, and do not skip the first
+		 * EDID_LENGTH bytes.
+		 */
+		start = 0x00;
+		msgs[1].len = total_size;
+		msgs[1].buf = block;
+
+		if (i2c_transfer(adapter, msgs, 2) != 2) {
+			DRM_ERROR("Unable to read EDID extension blocks.\n");
+			goto err;
+		}
+	}
+
+	return block;
+
+err:
+	kfree(block);
+	return NULL;
+}
+
+/*
+ * Get videomode specified in the devicetree.
+ * Return 1 on success, 0 otherwise.
+ */
+static int stdp4028_get_of_modes(struct drm_connector *connector)
+{
+	struct stdp4028 *stdp = connector_to_stdp4028(connector);
+	struct i2c_client *client = stdp->stdp4028_i2c;
+	struct drm_display_mode *mode;
+	struct device_node *np = client->dev.of_node;
+	struct display_timing timing;
+	struct videomode video_mode;
+	int ret;
+
+	ret = of_get_display_timing(np, "panel-timing", &timing);
+	if (ret < 0)
+		return 0;
+
+	videomode_from_timing(&timing, &video_mode);
+
+	mode = drm_mode_create(connector->dev);
+	if (!mode)
+		return 0;
+	drm_display_mode_from_videomode(&video_mode, mode);
+	mode->type |= DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+
+	drm_mode_probed_add(connector, mode);
+	return 1;
+}
+
+static int stdp4028_get_modes(struct drm_connector *connector)
+{
+	struct stdp4028 *stdp;
+	struct i2c_client *client;
+	int num_modes = 0;
+
+	stdp = connector_to_stdp4028(connector);
+	client = stdp->edid_i2c;
+
+	mutex_lock(&stdp->lock);
+
+	num_modes = stdp4028_get_of_modes(connector);
+	if (num_modes > 0) {
+		mutex_unlock(&stdp->lock);
+		return num_modes;
+	}
+
+	kfree(stdp->edid);
+	stdp->edid = (struct edid *) stdp4028_get_edid(client);
+
+	if (stdp->edid) {
+		drm_connector_update_edid_property(connector, stdp->edid);
+		num_modes = drm_add_edid_modes(connector, stdp->edid);
+	}
+
+	mutex_unlock(&stdp->lock);
+
+	return num_modes;
+}
+
+
+static enum drm_mode_status stdp4028_mode_valid(
+		 struct drm_connector *connector, struct drm_display_mode *mode)
+{
+	if (mode->clock > MAX_PIXEL_CLOCK) {
+		DRM_INFO("The pixel clock for the mode %s is too high, and not supported.",
+			 mode->name);
+		return MODE_CLOCK_HIGH;
+	}
+
+	return MODE_OK;
+}
+
+static const struct
+drm_connector_helper_funcs stdp4028_connector_helper_funcs = {
+	.get_modes = stdp4028_get_modes,
+	.mode_valid = stdp4028_mode_valid,
+};
+
+static enum drm_connector_status stdp4028_detect(
+		 struct drm_connector *connector, bool force)
+{
+	struct stdp4028 *stdp = connector_to_stdp4028(connector);
+	s32 link_state;
+
+	link_state = stdp_read(stdp, STDP4028_DPTX_STS_REG);
+
+	if (link_state == STDP4028_CON_STATE_CONNECTED)
+		return connector_status_connected;
+
+	if (link_state == 0)
+		return connector_status_disconnected;
+
+	return connector_status_unknown;
+}
+
+static const struct drm_connector_funcs stdp4028_connector_funcs = {
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.detect = stdp4028_detect,
+	.destroy = drm_connector_cleanup,
+	.reset = drm_atomic_helper_connector_reset,
+	.atomic_duplicate_state = drm_atomic_helper_connector_duplicate_state,
+	.atomic_destroy_state = drm_atomic_helper_connector_destroy_state,
+};
+
+static irqreturn_t stdp4028_irq_handler(int irq, void *dev_id)
+{
+	struct stdp4028 *stdp = dev_id;
+
+	mutex_lock(&stdp->lock);
+
+	stdp_write(stdp, STDP4028_DPTX_IRQ_STS_REG, STDP4028_DPTX_IRQ_CLEAR);
+
+	mutex_unlock(&stdp->lock);
+
+	if (stdp->connector.dev)
+		drm_kms_helper_hotplug_event(stdp->connector.dev);
+
+	return IRQ_HANDLED;
+}
+
+static int stdp4028_create_connector(struct drm_bridge *bridge)
+{
+	int ret;
+	struct stdp4028 *stdp
+			  = bridge_to_stdp4028(bridge);
+	struct drm_connector *connector = &stdp->connector;
+
+	if (!bridge->encoder) {
+		DRM_ERROR("Parent encoder object not found");
+		return -ENODEV;
+	}
+
+	if (stdp->stdp4028_i2c->irq)
+		connector->polled = DRM_CONNECTOR_POLL_HPD;
+	else
+		connector->polled = DRM_CONNECTOR_POLL_CONNECT |
+				    DRM_CONNECTOR_POLL_DISCONNECT;
+
+	drm_connector_helper_add(connector, &stdp4028_connector_helper_funcs);
+
+	ret = drm_connector_init(bridge->dev, connector,
+				 &stdp4028_connector_funcs,
+				 DRM_MODE_CONNECTOR_DisplayPort);
+	if (ret) {
+		DRM_ERROR("Failed to initialize connector with drm\n");
+		return ret;
+	}
+
+	return drm_connector_attach_encoder(connector, bridge->encoder);
+}
+
+static int stdp4028_attach(struct drm_bridge *bridge,
+			   enum drm_bridge_attach_flags flags)
+{
+	struct stdp4028 *stdp
+			  = bridge_to_stdp4028(bridge);
+
+	/* Configures the bridge to re-enable interrupts after each ack. */
+	stdp_write(stdp, STDP4028_IRQ_OUT_CONF_REG, STDP4028_DPTX_DP_IRQ_EN);
+
+	/* Enable interrupts */
+	stdp_write(stdp, STDP4028_DPTX_IRQ_EN_REG, STDP4028_DPTX_IRQ_CONFIG);
+
+	if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
+		return 0;
+
+	return stdp4028_create_connector(bridge);
+}
+
+static const struct drm_bridge_funcs stdp4028_funcs = {
+	.attach = stdp4028_attach,
+};
+
+static int stdp4028_probe(struct i2c_client *stdp4028_i2c,
+			  const struct i2c_device_id *id)
+{
+	struct device *dev = &stdp4028_i2c->dev;
+	struct stdp4028 *bridge;
+	int ret;
+	u32 edid_i2c_reg, channels, chan_cfg;
+	enum of_gpio_flags flags;
+	int reset_gpio, i;
+	int reg;
+
+	bridge = devm_kzalloc(dev, sizeof(*bridge), GFP_KERNEL);
+	if (!bridge)
+		return -ENOMEM;
+
+	mutex_init(&bridge->lock);
+
+	bridge->stdp4028_i2c = stdp4028_i2c;
+	bridge->bridge.driver_private = bridge;
+	i2c_set_clientdata(stdp4028_i2c, bridge);
+
+	reset_gpio = of_get_named_gpio_flags(dev->of_node,
+					     "reset-gpios", 0, &flags);
+	if (gpio_is_valid(reset_gpio)) {
+		unsigned long gpio_flags;
+
+		/*
+		 * We will set GPIO to "inactive" state instead of toggling
+		 * reset. If the chip is not ready we will return -EPROBE_DEFER
+		 * and retry later.
+		 */
+		if (!(flags & OF_GPIO_ACTIVE_LOW))
+			gpio_flags = GPIOF_ACTIVE_LOW | GPIOF_OUT_INIT_LOW;
+		else
+			gpio_flags = GPIOF_OUT_INIT_HIGH;
+		ret = devm_gpio_request_one(dev, reset_gpio, gpio_flags,
+					    "stdp-reset");
+		if (ret) {
+			dev_err(dev, "request GPIO failed (%d)\n", ret);
+			/* continue anyway */
+		} else {
+			bridge->reset_gpio = gpio_to_desc(reset_gpio);
+			udelay(100);
+		}
+	} else if (reset_gpio == -EPROBE_DEFER) {
+		return -EPROBE_DEFER;
+	}
+
+	ret = of_property_read_u32(dev->of_node, "channels", &channels);
+	if (ret)
+		channels = 1;
+	bridge->channels = channels;
+
+	ret = of_property_read_u32(dev->of_node, "chan-cfg", &chan_cfg);
+	if (ret)
+		chan_cfg = 0;
+	bridge->chan_cfg = chan_cfg;
+
+	ret = of_property_read_u32(dev->of_node, "edid-reg", &edid_i2c_reg);
+	if (ret) {
+		dev_warn(dev, "edid-reg not specified, assuming 0x50...\n");
+		edid_i2c_reg = 0x50;
+	}
+
+	/* Configure stdp registers */
+	reg = stdp_read(bridge, STDP4028_PRODUCT_ID_REG);
+	if (reg < 0) {
+		dev_err(dev, "Can't read stdp id (%d)\n", reg);
+		return -EPROBE_DEFER; /* probably, reset not complete */
+	}
+
+	dev_info(dev, "stdp id word: %x\n", reg);
+
+	for (i = 0; i < 10; i++) {
+		reg = stdp_read(bridge, STDP4028_IRQ_STS_REG);
+		if (reg > 0 && reg & 0x800)
+			break;
+		usleep_range(1000, 1500);
+	}
+	dev_dbg(dev, "STDP status word %x (i = %d)\n", reg, i);
+	stdp_write(bridge, STDP4028_IRQ_STS_REG, 0x800); //clear
+	/* enable edid addr */
+	stdp_write(bridge, STDP4028_I2C_CTRL_REG, (edid_i2c_reg << 1) | 0x400);
+
+	if (channels == 4)
+		reg = 2;
+	else if (channels == 2)
+		reg = 1;
+	else
+		reg = 0;
+	reg |= chan_cfg << 2;
+	stdp_write(bridge, STDP4028_LVDS_CTRL0_REG, reg);
+
+	bridge->edid_i2c = i2c_new_dummy_device(stdp4028_i2c->adapter, edid_i2c_reg);
+
+	if (!bridge->edid_i2c)
+		return -ENOMEM;
+
+	bridge->bridge.funcs = &stdp4028_funcs;
+	bridge->bridge.of_node = dev->of_node;
+	drm_bridge_add(&bridge->bridge);
+
+	/* Clear pending interrupts since power up. */
+	stdp_write(bridge, STDP4028_DPTX_IRQ_STS_REG, STDP4028_DPTX_IRQ_CLEAR);
+
+	if (stdp4028_i2c->irq) {
+		ret = devm_request_threaded_irq(&stdp4028_i2c->dev,
+					stdp4028_i2c->irq, NULL,
+					stdp4028_irq_handler,
+					IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+					"stdp-lvds-dp", bridge);
+		if (ret)
+			return ret;
+
+		/* enable DPTX IRQs */
+		stdp_write(bridge, STDP4028_IRQ_OUT_CONF_REG,
+			   STDP4028_DPTX_DP_IRQ_EN);
+		stdp_write(bridge, STDP4028_DPTX_IRQ_EN_REG,
+			   STDP4028_DPTX_IRQ_CONFIG);
+	}
+
+	return 0;
+}
+
+static int stdp4028_remove(struct i2c_client *stdp4028_i2c)
+{
+	struct stdp4028 *stdp =	i2c_get_clientdata(stdp4028_i2c);
+
+	drm_bridge_remove(&stdp->bridge);
+	i2c_unregister_device(stdp->edid_i2c);
+
+	kfree(stdp->edid);
+
+	return 0;
+}
+
+static const struct i2c_device_id stdp4028_i2c_table[] = {
+	{"stdp4028-lvds-dp", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, stdp4028_i2c_table);
+
+static const struct of_device_id stdp4028_match[] = {
+	{ .compatible = "megachips,stdp4028-lvds-dp" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stdp4028_match);
+
+static struct i2c_driver stdp4028_driver = {
+	.id_table	= stdp4028_i2c_table,
+	.probe		= stdp4028_probe,
+	.remove		= stdp4028_remove,
+	.driver		= {
+		.name		= "stdp4028-lvds-dp",
+		.of_match_table	= stdp4028_match,
+	},
+};
+module_i2c_driver(stdp4028_driver);
+
+MODULE_AUTHOR("Vadim V. Vlasov <vvv19xx at gmail.com>");
+MODULE_DESCRIPTION("STDP4028 LVDS to DP display bridge)");
+MODULE_LICENSE("GPL v2");
-- 
2.32.0