[PATCH V3 3/4] drm/bridge: Drivers for megachips-stdpxxxx-ge-b850v3-fw (LVDS-DP++)

[Peter Senna Tschudin]

The video processing pipeline on the second output on the GE B850v3:

  Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output

Each bridge has a dedicated flash containing firmware for supporting the
custom design. The result is that in this design neither the STDP4028
nor the STDP2690 behave as the stock bridges would. The compatible
strings include the suffix "-ge-b850v3-fw" to make it clear that the
driver is for the bridges with the firmware which is specific for the GE
B850v3.

The driver is powerless to control the video processing pipeline, as the
two bridges behaves as a single one. The driver is only needed for
telling the host about EDID / HPD, and for giving the host powers to ack
interrupts.

This driver adds one i2c_device for each bridge, but only one
drm_bridge. This design allows the creation of a functional connector
that is capable of reading EDID from the STDP2690 while handling
interrupts on the STDP4028.

Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
Cc: Martyn Welch <martyn.welch@xxxxxxxxxxxxxxx>
Cc: Martin Donnelly <martin.donnelly@xxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>
Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Cc: Rob Herring <robh@xxxxxxxxxx>
Cc: Fabio Estevam <fabio.estevam@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Thierry Reding <treding@xxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: Archit Taneja <architt@xxxxxxxxxxxxxx>
Cc: Enric Balletbo <enric.balletbo@xxxxxxxxxxxxx>
Signed-off-by: Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx>
---
Changes from V2:
 - Fix the code to allow it be compiled as a module

Changes from V1:
 - Updated copyright year
 - Fixed blank line issues
 - Updated ge_b850v3_lvds_remove() to not rely on ge_b850v3_lvds_ptr->edid and
   added a comment to explain the test.
 - Fixed checkpatch strict warnings about continuation lines. In one case
   fixing the warning would cause the continuation line to be over 80 chars and
   that strict warning remains.

 drivers/gpu/drm/bridge/Kconfig                     |  11 +
 drivers/gpu/drm/bridge/Makefile                    |   1 +
 .../drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c   | 428 +++++++++++++++++++++
 3 files changed, 440 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index eb8688e..4a937f1 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -48,6 +48,17 @@ config DRM_DW_HDMI_I2S_AUDIO
 	  Support the I2S Audio interface which is part of the Synopsis
 	  Designware HDMI block.
 
+config DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW
+	tristate "MegaChips stdp4028-ge-b850v3-fw and stdp2690-ge-b850v3-fw"
+	depends on OF
+	select DRM_KMS_HELPER
+	select DRM_PANEL
+	---help---
+          This is a driver for the display bridges of
+          GE B850v3 that convert dual channel LVDS
+          to DP++. This is used with the i.MX6 imx-ldb
+          driver. You are likely to say N here.
+
 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 2e83a785..af0b7cc 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -5,6 +5,7 @@ obj-$(CONFIG_DRM_DUMB_VGA_DAC) += dumb-vga-dac.o
 obj-$(CONFIG_DRM_DW_HDMI) += dw-hdmi.o
 obj-$(CONFIG_DRM_DW_HDMI_AHB_AUDIO) += dw-hdmi-ahb-audio.o
 obj-$(CONFIG_DRM_DW_HDMI_I2S_AUDIO) += dw-hdmi-i2s-audio.o
+obj-$(CONFIG_DRM_MEGACHIPS_STDPXXXX_GE_B850V3_FW) += megachips-stdpxxxx-ge-b850v3-fw.o
 obj-$(CONFIG_DRM_NXP_PTN3460) += nxp-ptn3460.o
 obj-$(CONFIG_DRM_PARADE_PS8622) += parade-ps8622.o
 obj-$(CONFIG_DRM_SIL_SII8620) += sil-sii8620.o
diff --git a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
new file mode 100644
index 0000000..e53c243
--- /dev/null
+++ b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
@@ -0,0 +1,428 @@
+/*
+ * Driver for MegaChips STDP4028 with GE B850v3 firmware (LVDS-DP)
+ * Driver for MegaChips STDP2690 with GE B850v3 firmware (DP-DP++)
+
+ * Copyright (c) 2017, Collabora Ltd.
+ * Copyright (c) 2017, General Electric Company
+
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+
+ * This program is distributed in the hope 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.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+ * This driver creates a drm_bridge and a drm_connector for the LVDS to DP++
+ * display bridge of the GE B850v3. There are two physical bridges on the video
+ * signal pipeline: a STDP4028(LVDS to DP) and a STDP2690(DP to DP++). The
+ * physical bridges are automatically configured by the input video signal, and
+ * the driver has no access to the video processing pipeline. The driver is
+ * only needed to read EDID from the STDP2690 and to handle HPD events from the
+ * STDP4028. The driver communicates with both bridges over i2c. The video
+ * signal pipeline is as follows:
+ *
+ *   Host -> LVDS|--(STDP4028)--|DP -> DP|--(STDP2690)--|DP++ -> Video output
+ *
+ */
+
+#include <linux/gpio.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_crtc_helper.h>
+#include <drm/drm_edid.h>
+#include <drm/drmP.h>
+
+#define EDID_EXT_BLOCK_CNT 0x7E
+
+#define STDP4028_IRQ_OUT_CONF_REG 0x02
+#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 0x1000
+
+#define STDP4028_DPTX_HOTPLUG_IRQ_EN 0x0400
+#define STDP4028_DPTX_LINK_CH_IRQ_EN 0x2000
+#define STDP4028_DPTX_IRQ_CONFIG \
+		(STDP4028_DPTX_LINK_CH_IRQ_EN | STDP4028_DPTX_HOTPLUG_IRQ_EN)
+
+#define STDP4028_DPTX_HOTPLUG_STS 0x0200
+#define STDP4028_DPTX_LINK_STS 0x1000
+#define STDP4028_CON_STATE_CONNECTED \
+		(STDP4028_DPTX_HOTPLUG_STS | STDP4028_DPTX_LINK_STS)
+
+#define STDP4028_DPTX_HOTPLUG_CH_STS 0x0400
+#define STDP4028_DPTX_LINK_CH_STS 0x2000
+#define STDP4028_DPTX_IRQ_CLEAR \
+		(STDP4028_DPTX_LINK_CH_STS | STDP4028_DPTX_HOTPLUG_CH_STS)
+
+static DEFINE_MUTEX(ge_b850v3_lvds_dev_mutex);
+
+struct ge_b850v3_lvds {
+	struct drm_connector connector;
+	struct drm_bridge bridge;
+	struct i2c_client *stdp4028_i2c;
+	struct i2c_client *stdp2690_i2c;
+	struct edid *edid;
+};
+
+static struct ge_b850v3_lvds *ge_b850v3_lvds_ptr;
+
+u8 *stdp2690_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;
+		}
+		if (!drm_edid_block_valid(block, 1, false, NULL)) {
+			DRM_ERROR("Invalid EDID data\n");
+			goto err;
+		}
+	}
+
+	return block;
+
+err:
+	kfree(block);
+	return NULL;
+}
+
+static int ge_b850v3_lvds_get_modes(struct drm_connector *connector)
+{
+	struct i2c_client *client;
+	int num_modes = 0;
+
+	client = ge_b850v3_lvds_ptr->stdp2690_i2c;
+
+	kfree(ge_b850v3_lvds_ptr->edid);
+	ge_b850v3_lvds_ptr->edid = (struct edid *)stdp2690_get_edid(client);
+
+	if (ge_b850v3_lvds_ptr->edid) {
+		drm_mode_connector_update_edid_property(connector,
+						      ge_b850v3_lvds_ptr->edid);
+		num_modes = drm_add_edid_modes(connector,
+					       ge_b850v3_lvds_ptr->edid);
+	}
+
+	return num_modes;
+}
+
+static enum drm_mode_status ge_b850v3_lvds_mode_valid(
+		struct drm_connector *connector, struct drm_display_mode *mode)
+{
+	return MODE_OK;
+}
+
+static const struct
+drm_connector_helper_funcs ge_b850v3_lvds_connector_helper_funcs = {
+	.get_modes = ge_b850v3_lvds_get_modes,
+	.mode_valid = ge_b850v3_lvds_mode_valid,
+};
+
+static enum drm_connector_status ge_b850v3_lvds_detect(
+		struct drm_connector *connector, bool force)
+{
+	struct i2c_client *stdp4028_i2c =
+			ge_b850v3_lvds_ptr->stdp4028_i2c;
+	s32 link_state;
+
+	link_state = i2c_smbus_read_word_data(stdp4028_i2c,
+					      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 ge_b850v3_lvds_connector_funcs = {
+	.dpms = drm_atomic_helper_connector_dpms,
+	.fill_modes = drm_helper_probe_single_connector_modes,
+	.detect = ge_b850v3_lvds_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 ge_b850v3_lvds_irq_handler(int irq, void *dev_id)
+{
+	struct i2c_client *stdp4028_i2c
+			= ge_b850v3_lvds_ptr->stdp4028_i2c;
+
+	i2c_smbus_write_word_data(stdp4028_i2c,
+				  STDP4028_DPTX_IRQ_STS_REG,
+				  STDP4028_DPTX_IRQ_CLEAR);
+
+	if (ge_b850v3_lvds_ptr->connector.dev)
+		drm_kms_helper_hotplug_event(ge_b850v3_lvds_ptr->connector.dev);
+
+	return IRQ_HANDLED;
+}
+
+static int ge_b850v3_lvds_attach(struct drm_bridge *bridge)
+{
+	struct drm_connector *connector = &ge_b850v3_lvds_ptr->connector;
+	struct i2c_client *stdp4028_i2c
+			= ge_b850v3_lvds_ptr->stdp4028_i2c;
+	int ret;
+
+	if (!bridge->encoder) {
+		DRM_ERROR("Parent encoder object not found");
+		return -ENODEV;
+	}
+
+	connector->polled = DRM_CONNECTOR_POLL_HPD;
+
+	drm_connector_helper_add(connector,
+				 &ge_b850v3_lvds_connector_helper_funcs);
+
+	ret = drm_connector_init(bridge->dev, connector,
+				 &ge_b850v3_lvds_connector_funcs,
+				 DRM_MODE_CONNECTOR_DisplayPort);
+	if (ret) {
+		DRM_ERROR("Failed to initialize connector with drm\n");
+		return ret;
+	}
+
+	ret = drm_mode_connector_attach_encoder(connector, bridge->encoder);
+	if (ret)
+		return ret;
+
+	/* Configures the bridge to re-enable interrupts after each ack. */
+	i2c_smbus_write_word_data(stdp4028_i2c,
+				  STDP4028_IRQ_OUT_CONF_REG,
+				  STDP4028_DPTX_DP_IRQ_EN);
+
+	/* Enable interrupts */
+	i2c_smbus_write_word_data(stdp4028_i2c,
+				  STDP4028_DPTX_IRQ_EN_REG,
+				  STDP4028_DPTX_IRQ_CONFIG);
+
+	return 0;
+}
+
+static const struct drm_bridge_funcs ge_b850v3_lvds_funcs = {
+	.attach = ge_b850v3_lvds_attach,
+};
+
+static int ge_b850v3_lvds_init(struct device *dev)
+{
+	mutex_lock(&ge_b850v3_lvds_dev_mutex);
+
+	if (ge_b850v3_lvds_ptr)
+		goto success;
+
+	ge_b850v3_lvds_ptr = devm_kzalloc(dev,
+					  sizeof(*ge_b850v3_lvds_ptr),
+					  GFP_KERNEL);
+
+	if (!ge_b850v3_lvds_ptr) {
+		mutex_unlock(&ge_b850v3_lvds_dev_mutex);
+		return -ENOMEM;
+	}
+
+	ge_b850v3_lvds_ptr->bridge.funcs = &ge_b850v3_lvds_funcs;
+	ge_b850v3_lvds_ptr->bridge.of_node = dev->of_node;
+	drm_bridge_add(&ge_b850v3_lvds_ptr->bridge);
+
+success:
+	mutex_unlock(&ge_b850v3_lvds_dev_mutex);
+	return 0;
+}
+
+static void ge_b850v3_lvds_remove(void)
+{
+	mutex_lock(&ge_b850v3_lvds_dev_mutex);
+	/*
+	 * This check is to avoid both the drivers
+	 * removing the bridge in their remove() function
+	 */
+	if (!ge_b850v3_lvds_ptr)
+		goto out;
+
+	drm_bridge_remove(&ge_b850v3_lvds_ptr->bridge);
+
+	kfree(ge_b850v3_lvds_ptr->edid);
+
+	ge_b850v3_lvds_ptr = NULL;
+out:
+	mutex_unlock(&ge_b850v3_lvds_dev_mutex);
+}
+
+static int stdp4028_ge_b850v3_fw_probe(struct i2c_client *stdp4028_i2c,
+				       const struct i2c_device_id *id)
+{
+	struct device *dev = &stdp4028_i2c->dev;
+
+	ge_b850v3_lvds_init(dev);
+
+	ge_b850v3_lvds_ptr->stdp4028_i2c = stdp4028_i2c;
+	i2c_set_clientdata(stdp4028_i2c, ge_b850v3_lvds_ptr);
+
+	/* Clear pending interrupts since power up. */
+	i2c_smbus_write_word_data(stdp4028_i2c,
+				  STDP4028_DPTX_IRQ_STS_REG,
+				  STDP4028_DPTX_IRQ_CLEAR);
+
+	if (!stdp4028_i2c->irq)
+		return 0;
+
+	return devm_request_threaded_irq(&stdp4028_i2c->dev,
+			stdp4028_i2c->irq, NULL,
+			ge_b850v3_lvds_irq_handler,
+			IRQF_TRIGGER_HIGH | IRQF_ONESHOT,
+			"ge-b850v3-lvds-dp", ge_b850v3_lvds_ptr);
+}
+
+static int stdp4028_ge_b850v3_fw_remove(struct i2c_client *stdp4028_i2c)
+{
+	ge_b850v3_lvds_remove();
+
+	return 0;
+}
+
+static const struct i2c_device_id stdp4028_ge_b850v3_fw_i2c_table[] = {
+	{"stdp4028_ge_fw", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, stdp4028_ge_b850v3_fw_i2c_table);
+
+static const struct of_device_id stdp4028_ge_b850v3_fw_match[] = {
+	{ .compatible = "megachips,stdp4028-ge-b850v3-fw" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stdp4028_ge_b850v3_fw_match);
+
+static struct i2c_driver stdp4028_ge_b850v3_fw_driver = {
+	.id_table	= stdp4028_ge_b850v3_fw_i2c_table,
+	.probe		= stdp4028_ge_b850v3_fw_probe,
+	.remove		= stdp4028_ge_b850v3_fw_remove,
+	.driver		= {
+		.name		= "stdp4028-ge-b850v3-fw",
+		.of_match_table = stdp4028_ge_b850v3_fw_match,
+	},
+};
+
+static int stdp2690_ge_b850v3_fw_probe(struct i2c_client *stdp2690_i2c,
+				       const struct i2c_device_id *id)
+{
+	struct device *dev = &stdp2690_i2c->dev;
+
+	ge_b850v3_lvds_init(dev);
+
+	ge_b850v3_lvds_ptr->stdp2690_i2c = stdp2690_i2c;
+	i2c_set_clientdata(stdp2690_i2c, ge_b850v3_lvds_ptr);
+
+	return 0;
+}
+
+static int stdp2690_ge_b850v3_fw_remove(struct i2c_client *stdp2690_i2c)
+{
+	ge_b850v3_lvds_remove();
+
+	return 0;
+}
+
+static const struct i2c_device_id stdp2690_ge_b850v3_fw_i2c_table[] = {
+	{"stdp2690_ge_fw", 0},
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, stdp2690_ge_b850v3_fw_i2c_table);
+
+static const struct of_device_id stdp2690_ge_b850v3_fw_match[] = {
+	{ .compatible = "megachips,stdp2690-ge-b850v3-fw" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stdp2690_ge_b850v3_fw_match);
+
+static struct i2c_driver stdp2690_ge_b850v3_fw_driver = {
+	.id_table	= stdp2690_ge_b850v3_fw_i2c_table,
+	.probe		= stdp2690_ge_b850v3_fw_probe,
+	.remove		= stdp2690_ge_b850v3_fw_remove,
+	.driver		= {
+		.name		= "stdp2690-ge-b850v3-fw",
+		.of_match_table = stdp2690_ge_b850v3_fw_match,
+	},
+};
+
+static int __init stdpxxxx_ge_b850v3_init(void)
+{
+	int ret;
+
+	ret = i2c_add_driver(&stdp4028_ge_b850v3_fw_driver);
+	if (ret)
+		return ret;
+
+	return i2c_add_driver(&stdp2690_ge_b850v3_fw_driver);
+}
+module_init(stdpxxxx_ge_b850v3_init);
+
+static void __exit stdpxxxx_ge_b850v3_exit(void)
+{
+	i2c_del_driver(&stdp2690_ge_b850v3_fw_driver);
+	i2c_del_driver(&stdp4028_ge_b850v3_fw_driver);
+}
+module_exit(stdpxxxx_ge_b850v3_exit);
+
+MODULE_AUTHOR("Peter Senna Tschudin <peter.senna@xxxxxxxxxxxxx>");
+MODULE_AUTHOR("Martyn Welch <martyn.welch@xxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("GE LVDS to DP++ display bridge)");
+MODULE_LICENSE("GPL v2");
-- 
2.9.3