[PATCH v6 0/2] Add support for ANX7688

[PATCH v6 0/2] Add support for ANX7688

[Dafna Hirschfeld]

ANX7688 is a typec port controller that also converts HDMI to DP.
ANX7688 is found on Acer Chromebook R13 (elm) and on Pine64 PinePhone.

On Acer Chromebook R13 (elm), the device is powered-up and controller by the
Embedded Controller. Therefore its operation is transparent
to the SoC. It is used in elm only as a display bridge driver.
The bridge driver only reads some values using i2c and use them to
implement the mode_fixup cb.

On v5 we added the full dt-binding of the generic Analogix anx7688 device.
The problem is that for elm, most of the fields are not needed since
the anx7688 sits behind the EC. After a discussion on v5 (see [1])
we decided to go back to the original approach and send the dt binding
as specific to the elm. So in this version we rename the device to cros_ec_anx7688
and use the compatible 'google,cros-ec-anx7688'.

[1] https://patchwork.kernel.org/project/dri-devel/patch/20210305124351.15079-3-dafna.hirschfeld@collabora.com/

Changes since v5:
* treat the device as a specific combination of an ANX7688 behind the EC and
call it 'cros-ec-anx7688'

Changes since v4:
In v4 of this set, the device was added as an 'mfd' device
and an additional 'bridge' device for the HDMI-DP conversion, see [2].

[2] https://lkml.org/lkml/2020/3/18/64

Dafna Hirschfeld (1):
  dt-bindings: display: add google,cros-ec-anx7688.yaml

Enric Balletbo i Serra (1):
  drm/bridge: Add ChromeOS EC ANX7688 bridge driver support

 .../bridge/google,cros-ec-anx7688.yaml        |  82 ++++++++
 drivers/gpu/drm/bridge/Kconfig                |  12 ++
 drivers/gpu/drm/bridge/Makefile               |   1 +
 drivers/gpu/drm/bridge/cros-ec-anx7688.c      | 191 ++++++++++++++++++
 4 files changed, 286 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml
 create mode 100644 drivers/gpu/drm/bridge/cros-ec-anx7688.c

-- 
2.17.1

[PATCH v6 1/2] dt-bindings: display: add google,cros-ec-anx7688.yaml

[Dafna Hirschfeld]

ChromeOS EC ANX7688 is a display bridge that converts HDMI 2.0 to
DisplayPort 1.3 Ultra-HDi (4096x2160p60). It is an Analogix ANX7688 chip
which is connected to and operated by the ChromeOS Embedded Controller
(See google,cros-ec.yaml). It is accessed using I2C tunneling through
the EC and therefore its node should be a child of an EC I2C tunnel node
(See google,cros-ec-i2c-tunnel.yaml).

ChromOS EC ANX7688 is found on Acer Chromebook R13 (elm)

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
---
 .../bridge/google,cros-ec-anx7688.yaml        | 82 +++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml

diff --git a/Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml b/Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml
new file mode 100644
index 000000000000..9f7cc6b757cb
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml
@@ -0,0 +1,82 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/google,cros-ec-anx7688.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ChromeOS EC ANX7688 HDMI to DP Converter through Type-C Port
+
+maintainers:
+  - Nicolas Boichat <drinkcat@chromium.org>
+  - Enric Balletbo i Serra <enric.balletbo@collabora.com>
+
+description: |
+  ChromeOS EC ANX7688 is a display bridge that converts HDMI 2.0 to
+  DisplayPort 1.3 Ultra-HDi (4096x2160p60). It is an Analogix ANX7688 chip
+  which is connected to and operated by the ChromeOS Embedded Controller
+  (See google,cros-ec.yaml). It is accessed using I2C tunneling through
+  the EC and therefore its node should be a child of an EC I2C tunnel node
+  (See google,cros-ec-i2c-tunnel.yaml).
+
+properties:
+  compatible:
+    const: google,cros-ec-anx7688
+
+  reg:
+    maxItems: 1
+    description: I2C address of the device.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for HDMI input.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: USB Type-c connector.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c_tunnel_b: i2c-tunnel1 {
+        compatible = "google,cros-ec-i2c-tunnel";
+        google,remote-bus = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        anx7688: anx7688@2c {
+            compatible = "google,cros-ec-anx7688";
+            reg = <0x2c>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                port@0 {
+                    reg = <0>;
+                    anx7688_in: endpoint {
+                        remote-endpoint = <&hdmi0_out>;
+                    };
+                };
+                port@1 {
+                    reg = <1>;
+                    anx7688_out: endpoint {
+                        remote-endpoint = <&typec_connector>;
+                    };
+                };
+            };
+        };
+    };
+
-- 
2.17.1

[PATCH v6 2/2] drm/bridge: Add ChromeOS EC ANX7688 bridge driver support

[Dafna Hirschfeld]

From: Enric Balletbo i Serra <enric.balletbo@collabora.com>

This driver adds support for the ChromeOS EC ANX7688 HDMI to DP converter

For our use case, the only reason the Linux kernel driver is necessary is
to reject resolutions that require more bandwidth than what is available
on the DP side. DP bandwidth and lane count are reported by the bridge via
2 registers and, as far as we know, only chips that have a firmware
version greater than 0.85 support these two registers.

Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>
[The driver is OF only so should depends on CONFIG_OF]
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
[convert to i2c driver, rename to cros_ec_anx7688, add err checks]
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/gpu/drm/bridge/Kconfig           |  12 ++
 drivers/gpu/drm/bridge/Makefile          |   1 +
 drivers/gpu/drm/bridge/cros-ec-anx7688.c | 191 +++++++++++++++++++++++
 3 files changed, 204 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/cros-ec-anx7688.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 998dcda44f70..9f991f0551ce 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -37,6 +37,18 @@ config DRM_CHRONTEL_CH7033
 
 	  If in doubt, say "N".
 
+config DRM_CROS_EC_ANX7688
+	tristate "ChromeOS EC ANX7688 bridge"
+	depends on OF
+	select DRM_KMS_HELPER
+	select REGMAP_I2C
+	help
+	  ChromeOS EC ANX7688 is an ultra-low power
+	  4K Ultra-HD (4096x2160p60) mobile HD transmitter
+	  designed for ChromeOS devices. It converts HDMI
+	  2.0 to DisplayPort 1.3 Ultra-HD. It is connected
+	  to the ChromeOS Embedded Controller.
+
 config DRM_DISPLAY_CONNECTOR
 	tristate "Display connector support"
 	depends on OF
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index 0fc37a8e38d0..a6261b89087c 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DRM_CDNS_DSI) += cdns-dsi.o
 obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
+obj-$(CONFIG_DRM_CROS_EC_ANX7688) += cros-ec-anx7688.o
 obj-$(CONFIG_DRM_DISPLAY_CONNECTOR) += display-connector.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611) += lontium-lt9611.o
 obj-$(CONFIG_DRM_LONTIUM_LT9611UXC) += lontium-lt9611uxc.o
diff --git a/drivers/gpu/drm/bridge/cros-ec-anx7688.c b/drivers/gpu/drm/bridge/cros-ec-anx7688.c
new file mode 100644
index 000000000000..0f6d907432e3
--- /dev/null
+++ b/drivers/gpu/drm/bridge/cros-ec-anx7688.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * CrOS EC ANX7688 HDMI->DP bridge driver
+ *
+ * Copyright 2020 Google LLC
+ */
+
+#include <drm/drm_bridge.h>
+#include <drm/drm_print.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+/* Register addresses */
+#define ANX7688_VENDOR_ID_REG		0x00
+#define ANX7688_DEVICE_ID_REG		0x02
+
+#define ANX7688_FW_VERSION_REG		0x80
+
+#define ANX7688_DP_BANDWIDTH_REG	0x85
+#define ANX7688_DP_LANE_COUNT_REG	0x86
+
+#define ANX7688_VENDOR_ID		0x1f29
+#define ANX7688_DEVICE_ID		0x7688
+
+/* First supported firmware version (0.85) */
+#define ANX7688_MINIMUM_FW_VERSION	0x0085
+
+static const struct regmap_config cros_ec_anx7688_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+struct cros_ec_anx7688 {
+	struct i2c_client *client;
+	struct regmap *regmap;
+	struct drm_bridge bridge;
+	bool filter;
+};
+
+static inline struct cros_ec_anx7688 *
+bridge_to_cros_ec_anx7688(struct drm_bridge *bridge)
+{
+	return container_of(bridge, struct cros_ec_anx7688, bridge);
+}
+
+static bool cros_ec_anx7688_bridge_mode_fixup(struct drm_bridge *bridge,
+					      const struct drm_display_mode *mode,
+					      struct drm_display_mode *adjusted_mode)
+{
+	struct cros_ec_anx7688 *anx = bridge_to_cros_ec_anx7688(bridge);
+	int totalbw, requiredbw;
+	u8 dpbw, lanecount;
+	u8 regs[2];
+	int ret;
+
+	if (!anx->filter)
+		return true;
+
+	/* Read both regs 0x85 (bandwidth) and 0x86 (lane count). */
+	ret = regmap_bulk_read(anx->regmap, ANX7688_DP_BANDWIDTH_REG, regs, 2);
+	if (ret < 0) {
+		DRM_ERROR("Failed to read bandwidth/lane count\n");
+		return false;
+	}
+	dpbw = regs[0];
+	lanecount = regs[1];
+
+	/* Maximum 0x19 bandwidth (6.75 Gbps Turbo mode), 2 lanes */
+	if (dpbw > 0x19 || lanecount > 2) {
+		DRM_ERROR("Invalid bandwidth/lane count (%02x/%d)\n", dpbw,
+			  lanecount);
+		return false;
+	}
+
+	/* Compute available bandwidth (kHz) */
+	totalbw = dpbw * lanecount * 270000 * 8 / 10;
+
+	/* Required bandwidth (8 bpc, kHz) */
+	requiredbw = mode->clock * 8 * 3;
+
+	DRM_DEBUG_KMS("DP bandwidth: %d kHz (%02x/%d); mode requires %d Khz\n",
+		      totalbw, dpbw, lanecount, requiredbw);
+
+	if (totalbw == 0) {
+		DRM_ERROR("Bandwidth/lane count are 0, not rejecting modes\n");
+		return true;
+	}
+
+	return totalbw >= requiredbw;
+}
+
+static const struct drm_bridge_funcs cros_ec_anx7688_bridge_funcs = {
+	.mode_fixup = cros_ec_anx7688_bridge_mode_fixup,
+};
+
+static int cros_ec_anx7688_bridge_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct cros_ec_anx7688 *anx7688;
+	u16 vendor, device, fw_version;
+	u8 buffer[4];
+	int ret;
+
+	anx7688 = devm_kzalloc(dev, sizeof(*anx7688), GFP_KERNEL);
+	if (!anx7688)
+		return -ENOMEM;
+
+	anx7688->client = client;
+	i2c_set_clientdata(client, anx7688);
+
+	anx7688->regmap = devm_regmap_init_i2c(client, &cros_ec_anx7688_regmap_config);
+	if (IS_ERR(anx7688->regmap)) {
+		ret = PTR_ERR(anx7688->regmap);
+		dev_err(dev, "regmap i2c init failed: %d\n", ret);
+		return ret;
+	}
+
+	/* Read both vendor and device id (4 bytes). */
+	ret = regmap_bulk_read(anx7688->regmap, ANX7688_VENDOR_ID_REG,
+			       buffer, 4);
+	if (ret) {
+		dev_err(dev, "Failed to read chip vendor/device id\n");
+		return ret;
+	}
+
+	vendor = (u16)buffer[1] << 8 | buffer[0];
+	device = (u16)buffer[3] << 8 | buffer[2];
+	if (vendor != ANX7688_VENDOR_ID || device != ANX7688_DEVICE_ID) {
+		dev_err(dev, "Invalid vendor/device id %04x/%04x\n",
+			vendor, device);
+		return -ENODEV;
+	}
+
+	ret = regmap_bulk_read(anx7688->regmap, ANX7688_FW_VERSION_REG,
+			       buffer, 2);
+	if (ret) {
+		dev_err(dev, "Failed to read firmware version\n");
+		return ret;
+	}
+
+	fw_version = (u16)buffer[0] << 8 | buffer[1];
+	dev_info(dev, "ANX7688 firmware version 0x%04x\n", fw_version);
+
+	anx7688->bridge.of_node = dev->of_node;
+
+	/* FW version >= 0.85 supports bandwidth/lane count registers */
+	if (fw_version >= ANX7688_MINIMUM_FW_VERSION)
+		anx7688->filter = true;
+	else
+		/* Warn, but not fail, for backwards compatibility */
+		DRM_WARN("Old ANX7688 FW version (0x%04x), not filtering\n",
+			 fw_version);
+
+	anx7688->bridge.funcs = &cros_ec_anx7688_bridge_funcs;
+	drm_bridge_add(&anx7688->bridge);
+
+	return 0;
+}
+
+static int cros_ec_anx7688_bridge_remove(struct i2c_client *client)
+{
+	struct cros_ec_anx7688 *anx7688 = i2c_get_clientdata(client);
+
+	drm_bridge_remove(&anx7688->bridge);
+
+	return 0;
+}
+
+static const struct of_device_id cros_ec_anx7688_bridge_match_table[] = {
+	{ .compatible = "google,cros-ec-anx7688" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, cros_ec_anx7688_bridge_match_table);
+
+static struct i2c_driver cros_ec_anx7688_bridge_driver = {
+	.probe_new = cros_ec_anx7688_bridge_probe,
+	.remove = cros_ec_anx7688_bridge_remove,
+	.driver = {
+		.name = "cros-ec-anx7688-bridge",
+		.of_match_table = cros_ec_anx7688_bridge_match_table,
+	},
+};
+
+module_i2c_driver(cros_ec_anx7688_bridge_driver);
+
+MODULE_DESCRIPTION("ChromeOS EC ANX7688 HDMI->DP bridge driver");
+MODULE_AUTHOR("Nicolas Boichat <drinkcat@chromium.org>");
+MODULE_AUTHOR("Enric Balletbo i Serra <enric.balletbo@collabora.com>");
+MODULE_LICENSE("GPL");
-- 
2.17.1

Re: [PATCH v6 1/2] dt-bindings: display: add google,cros-ec-anx7688.yaml

[Rob Herring]

On Fri, 09 Apr 2021 18:19:50 +0200, Dafna Hirschfeld wrote:
> ChromeOS EC ANX7688 is a display bridge that converts HDMI 2.0 to
> DisplayPort 1.3 Ultra-HDi (4096x2160p60). It is an Analogix ANX7688 chip
> which is connected to and operated by the ChromeOS Embedded Controller
> (See google,cros-ec.yaml). It is accessed using I2C tunneling through
> the EC and therefore its node should be a child of an EC I2C tunnel node
> (See google,cros-ec-i2c-tunnel.yaml).
> 
> ChromOS EC ANX7688 is found on Acer Chromebook R13 (elm)
> 
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
> ---
>  .../bridge/google,cros-ec-anx7688.yaml        | 82 +++++++++++++++++++
>  1 file changed, 82 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH v6 0/2] Add support for ANX7688

[Dafna Hirschfeld]

Hi, pinging here, can one of the kernel bridge maintainers review this patchset?

Thanks,
Dafna

On 09.04.21 18:19, Dafna Hirschfeld wrote:
> ANX7688 is a typec port controller that also converts HDMI to DP.
> ANX7688 is found on Acer Chromebook R13 (elm) and on Pine64 PinePhone.
> 
> On Acer Chromebook R13 (elm), the device is powered-up and controller by the
> Embedded Controller. Therefore its operation is transparent
> to the SoC. It is used in elm only as a display bridge driver.
> The bridge driver only reads some values using i2c and use them to
> implement the mode_fixup cb.
> 
> On v5 we added the full dt-binding of the generic Analogix anx7688 device.
> The problem is that for elm, most of the fields are not needed since
> the anx7688 sits behind the EC. After a discussion on v5 (see [1])
> we decided to go back to the original approach and send the dt binding
> as specific to the elm. So in this version we rename the device to cros_ec_anx7688
> and use the compatible 'google,cros-ec-anx7688'.
> 
> [1] https://patchwork.kernel.org/project/dri-devel/patch/20210305124351.15079-3-dafna.hirschfeld@collabora.com/
> 
> Changes since v5:
> * treat the device as a specific combination of an ANX7688 behind the EC and
> call it 'cros-ec-anx7688'
> 
> Changes since v4:
> In v4 of this set, the device was added as an 'mfd' device
> and an additional 'bridge' device for the HDMI-DP conversion, see [2].
> 
> [2] https://lkml.org/lkml/2020/3/18/64
> 
> Dafna Hirschfeld (1):
>    dt-bindings: display: add google,cros-ec-anx7688.yaml
> 
> Enric Balletbo i Serra (1):
>    drm/bridge: Add ChromeOS EC ANX7688 bridge driver support
> 
>   .../bridge/google,cros-ec-anx7688.yaml        |  82 ++++++++
>   drivers/gpu/drm/bridge/Kconfig                |  12 ++
>   drivers/gpu/drm/bridge/Makefile               |   1 +
>   drivers/gpu/drm/bridge/cros-ec-anx7688.c      | 191 ++++++++++++++++++
>   4 files changed, 286 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml
>   create mode 100644 drivers/gpu/drm/bridge/cros-ec-anx7688.c
>