[PATCH 0/3] cec-gpio: add HDMI CEC GPIO-based driver

[PATCH 0/3] cec-gpio: add HDMI CEC GPIO-based driver

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>

This driver adds support for CEC implementations that use a pull-up
GPIO pin. While SoCs exist that do this, the primary use-case is to
turn a single-board computer into a cheap CEC debugger.

Together with 'cec-ctl --monitor-pin' you can do low-level CEC bus
monitoring and do protocol analysis. And error injection is also
planned for the future.

Here is an example using the Raspberry Pi 3:

https://hverkuil.home.xs4all.nl/rpi3-cec.jpg

A patch for the Raspberry Pi 2B/3 is added below for reference.
It uses pin 7 aka BCM4 aka GPCLK0 on the GPIO pin header.

While this example is for the Rpi, this driver will work for any
SoC with a pull-up GPIO pin.

I have one question: is there a generic way to check/force the gpio
to pull-up mode? I have not found that, but I am no gpio-expert.

Regards,

	Hans

--- cut here ---
diff --git a/arch/arm/boot/dts/bcm2836-rpi-2-b.dts b/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
index bf19e8cfb9e6..8cb82a70f33d 100644
--- a/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
+++ b/arch/arm/boot/dts/bcm2836-rpi-2-b.dts
@@ -24,6 +24,11 @@
 			linux,default-trigger = "default-on";
 		};
 	};
+
+	cec-gpio {
+		compatible = "cec-gpio";
+		gpio = <&gpio 4 GPIO_ACTIVE_HIGH>;
+	};
 };
 
 &gpio {
diff --git a/arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts b/arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts
index 972f14db28ac..cd0ec70732f4 100644
--- a/arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts
+++ b/arch/arm64/boot/dts/broadcom/bcm2837-rpi-3-b.dts
@@ -17,6 +17,11 @@
 			gpios = <&gpio 47 0>;
 		};
 	};
+
+	cec-gpio {
+		compatible = "cec-gpio";
+		gpio = <&gpio 4 GPIO_ACTIVE_HIGH>;
+	};
 };
 
 &uart1 {
--- cut here ---


Hans Verkuil (3):
  dt-bindings: document the CEC GPIO bindings
  cec-gpio: add HDMI CEC GPIO driver
  MAINTAINERS: add cec-gpio entry

 .../devicetree/bindings/media/cec-gpio.txt         |  18 ++
 MAINTAINERS                                        |   9 +
 drivers/media/platform/Kconfig                     |  10 ++
 drivers/media/platform/Makefile                    |   2 +
 drivers/media/platform/cec-gpio/Makefile           |   1 +
 drivers/media/platform/cec-gpio/cec-gpio.c         | 190 +++++++++++++++++++++
 6 files changed, 230 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/cec-gpio.txt
 create mode 100644 drivers/media/platform/cec-gpio/Makefile
 create mode 100644 drivers/media/platform/cec-gpio/cec-gpio.c

-- 
2.13.2

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[PATCH 1/3] dt-bindings: document the CEC GPIO bindings

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>

Document the bindings for the cec-gpio module for hardware where the
CEC pin is connected to a GPIO pin.

Signed-off-by: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
---
 Documentation/devicetree/bindings/media/cec-gpio.txt | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/media/cec-gpio.txt

diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt
new file mode 100644
index 000000000000..58fa56080cda
--- /dev/null
+++ b/Documentation/devicetree/bindings/media/cec-gpio.txt
@@ -0,0 +1,18 @@
+* HDMI CEC GPIO driver
+
+The HDMI CEC GPIO module supports CEC implementations where the CEC pin
+is hooked up to a pull-up GPIO pin.
+
+The CEC GPIO
+
+Required properties:
+  - compatible: value must be "cec-gpio"
+  - gpio: gpio that the CEC line is connected to
+
+Example for the Raspberry Pi 3 where the CEC line is connected to
+pin 7 aka BCM4 aka GPCLK0 on the GPIO pin header:
+
+cec-gpio {
+       compatible = "cec-gpio";
+       gpio = <&gpio 4 GPIO_ACTIVE_HIGH>;
+};
-- 
2.13.2

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Re: [PATCH 1/3] dt-bindings: document the CEC GPIO bindings

[Hans Verkuil]

On 02/08/17 10:42, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
> 
> Document the bindings for the cec-gpio module for hardware where the
> CEC pin is connected to a GPIO pin.

ping?

> 
> Signed-off-by: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
> ---
>  Documentation/devicetree/bindings/media/cec-gpio.txt | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/media/cec-gpio.txt
> 
> diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt
> new file mode 100644
> index 000000000000..58fa56080cda
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt
> @@ -0,0 +1,18 @@
> +* HDMI CEC GPIO driver
> +
> +The HDMI CEC GPIO module supports CEC implementations where the CEC pin
> +is hooked up to a pull-up GPIO pin.
> +
> +The CEC GPIO
> +
> +Required properties:
> +  - compatible: value must be "cec-gpio"
> +  - gpio: gpio that the CEC line is connected to
> +
> +Example for the Raspberry Pi 3 where the CEC line is connected to
> +pin 7 aka BCM4 aka GPCLK0 on the GPIO pin header:
> +
> +cec-gpio {
> +       compatible = "cec-gpio";
> +       gpio = <&gpio 4 GPIO_ACTIVE_HIGH>;
> +};
> 

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Re: [PATCH 1/3] dt-bindings: document the CEC GPIO bindings

[Hans Verkuil]

On 10/08/17 10:03, Hans Verkuil wrote:
> On 02/08/17 10:42, Hans Verkuil wrote:
>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>
>> Document the bindings for the cec-gpio module for hardware where the
>> CEC pin is connected to a GPIO pin.
> 
> ping?
> 
>>
>> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>> ---
>>  Documentation/devicetree/bindings/media/cec-gpio.txt | 18 ++++++++++++++++++
>>  1 file changed, 18 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/media/cec-gpio.txt
>>
>> diff --git a/Documentation/devicetree/bindings/media/cec-gpio.txt b/Documentation/devicetree/bindings/media/cec-gpio.txt
>> new file mode 100644
>> index 000000000000..58fa56080cda
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/media/cec-gpio.txt
>> @@ -0,0 +1,18 @@
>> +* HDMI CEC GPIO driver

OK, reading your comments from an other bindings patch I realize that 'bindings
refer to hardware, not drivers'. I'll fix and repost :-)

Regards,

	Hans

>> +
>> +The HDMI CEC GPIO module supports CEC implementations where the CEC pin
>> +is hooked up to a pull-up GPIO pin.
>> +
>> +The CEC GPIO
>> +
>> +Required properties:
>> +  - compatible: value must be "cec-gpio"
>> +  - gpio: gpio that the CEC line is connected to
>> +
>> +Example for the Raspberry Pi 3 where the CEC line is connected to
>> +pin 7 aka BCM4 aka GPCLK0 on the GPIO pin header:
>> +
>> +cec-gpio {
>> +       compatible = "cec-gpio";
>> +       gpio = <&gpio 4 GPIO_ACTIVE_HIGH>;
>> +};
>>
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

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[PATCH 3/3] MAINTAINERS: add cec-gpio entry

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>

Add an entry for the CEC GPIO driver.

Signed-off-by: Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
---
 MAINTAINERS | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index aeb84877854b..d85959f82a09 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3199,6 +3199,15 @@ F:	include/uapi/linux/cec.h
 F:	include/uapi/linux/cec-funcs.h
 F:	Documentation/devicetree/bindings/media/cec.txt
 
+CEC GPIO DRIVER
+M:	Hans Verkuil <hans.verkuil-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
+L:	linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
+T:	git git://linuxtv.org/media_tree.git
+W:	http://linuxtv.org
+S:	Supported
+F:	drivers/media/platform/cec-gpio/
+F:	Documentation/devicetree/bindings/media/cec-gpio.txt
+
 CELL BROADBAND ENGINE ARCHITECTURE
 M:	Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
 L:	linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org
-- 
2.13.2

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[PATCH 2/3] cec-gpio: add HDMI CEC GPIO driver

[Hans Verkuil]

From: Hans Verkuil <hans.verkuil@cisco.com>

Add a simple HDMI CEC GPIO driver that sits on top of the cec-pin framework.

While I have heard of SoCs that use the GPIO pin for CEC (apparently an
early RockChip SoC used that), the main use-case of this driver is to
function as a debugging tool.

By connecting the CEC line to a GPIO pin on a Raspberry Pi 3 for example
it turns it into a CEC debugger and protocol analyzer.

With 'cec-ctl --monitor-pin' the CEC traffic can be analyzed.

But of course it can also be used with any hardware project where the
HDMI CEC pin is hooked up to a pull-up gpio pin.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
---
 drivers/media/platform/Kconfig             |  10 ++
 drivers/media/platform/Makefile            |   2 +
 drivers/media/platform/cec-gpio/Makefile   |   1 +
 drivers/media/platform/cec-gpio/cec-gpio.c | 190 +++++++++++++++++++++++++++++
 4 files changed, 203 insertions(+)
 create mode 100644 drivers/media/platform/cec-gpio/Makefile
 create mode 100644 drivers/media/platform/cec-gpio/cec-gpio.c

diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
index 0c741d12dbc9..681507727259 100644
--- a/drivers/media/platform/Kconfig
+++ b/drivers/media/platform/Kconfig
@@ -537,6 +537,16 @@ menuconfig CEC_PLATFORM_DRIVERS
 
 if CEC_PLATFORM_DRIVERS
 
+config CEC_GPIO
+	tristate "Generic GPIO-based CEC driver"
+	depends on PREEMPT
+	select CEC_CORE
+	select CEC_PIN
+	---help---
+	  This is a generic GPIO-based CEC driver.
+	  The CEC bus is present in the HDMI connector and enables communication
+	  between compatible devices.
+
 config VIDEO_SAMSUNG_S5P_CEC
        tristate "Samsung S5P CEC driver"
        depends on PLAT_S5P || ARCH_EXYNOS || COMPILE_TEST
diff --git a/drivers/media/platform/Makefile b/drivers/media/platform/Makefile
index 9beadc760467..d01cc1886ad1 100644
--- a/drivers/media/platform/Makefile
+++ b/drivers/media/platform/Makefile
@@ -26,6 +26,8 @@ obj-$(CONFIG_VIDEO_CODA) 		+= coda/
 
 obj-$(CONFIG_VIDEO_SH_VEU)		+= sh_veu.o
 
+obj-$(CONFIG_CEC_GPIO)			+= cec-gpio/
+
 obj-$(CONFIG_VIDEO_MEM2MEM_DEINTERLACE)	+= m2m-deinterlace.o
 
 obj-$(CONFIG_VIDEO_MUX)			+= video-mux.o
diff --git a/drivers/media/platform/cec-gpio/Makefile b/drivers/media/platform/cec-gpio/Makefile
new file mode 100644
index 000000000000..e82b258afa55
--- /dev/null
+++ b/drivers/media/platform/cec-gpio/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_CEC_GPIO) += cec-gpio.o
diff --git a/drivers/media/platform/cec-gpio/cec-gpio.c b/drivers/media/platform/cec-gpio/cec-gpio.c
new file mode 100644
index 000000000000..43e1d447ad98
--- /dev/null
+++ b/drivers/media/platform/cec-gpio/cec-gpio.c
@@ -0,0 +1,190 @@
+/*
+ * Copyright 2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
+ *
+ * This program is free software; you may redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/delay.h>
+#include <linux/platform_device.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/of_gpio.h>
+#include <media/cec-pin.h>
+
+struct cec_gpio {
+	struct cec_adapter	*adap;
+	struct device		*dev;
+	int			gpio;
+	int			irq;
+	bool			is_low;
+	bool			have_irq;
+};
+
+static bool cec_gpio_read(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (cec->is_low)
+		return false;
+	return gpio_get_value(cec->gpio);
+}
+
+static void cec_gpio_high(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (!cec->is_low)
+		return;
+	cec->is_low = false;
+	gpio_direction_input(cec->gpio);
+}
+
+static void cec_gpio_low(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (cec->is_low)
+		return;
+	if (WARN_ON_ONCE(cec->have_irq))
+		free_irq(cec->irq, cec);
+	cec->have_irq = false;
+	cec->is_low = true;
+	gpio_direction_output(cec->gpio, 0);
+}
+
+static irqreturn_t cec_gpio_irq_handler(int irq, void *priv)
+{
+	struct cec_gpio *cec = priv;
+
+	cec_pin_changed(cec->adap, gpio_get_value(cec->gpio));
+	return IRQ_HANDLED;
+}
+
+static bool cec_gpio_enable_irq(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (request_irq(cec->irq, cec_gpio_irq_handler,
+			IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+			adap->name, cec))
+		return false;
+	cec->have_irq = true;
+	return true;
+}
+
+static void cec_gpio_disable_irq(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (cec->have_irq)
+		free_irq(cec->irq, cec);
+	cec->have_irq = false;
+}
+
+static void cec_gpio_status(struct cec_adapter *adap, struct seq_file *file)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	seq_printf(file, "mode:   %s\n", cec->is_low ? "low-drive" : "read");
+	if (cec->have_irq)
+		seq_printf(file, "using irq: %d\n", cec->irq);
+}
+
+static void cec_gpio_free(struct cec_adapter *adap)
+{
+	struct cec_gpio *cec = cec_get_drvdata(adap);
+
+	if (cec->have_irq)
+		cec_gpio_disable_irq(adap);
+}
+
+static const struct cec_pin_ops cec_gpio_pin_ops = {
+	.read = cec_gpio_read,
+	.low = cec_gpio_low,
+	.high = cec_gpio_high,
+	.enable_irq = cec_gpio_enable_irq,
+	.disable_irq = cec_gpio_disable_irq,
+	.status = cec_gpio_status,
+	.free = cec_gpio_free,
+};
+
+static int cec_gpio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	enum of_gpio_flags hpd_gpio_flags;
+	struct cec_gpio *cec;
+	int ret;
+
+	cec = devm_kzalloc(dev, sizeof(*cec), GFP_KERNEL);
+	if (!cec)
+		return -ENOMEM;
+
+	cec->gpio = of_get_named_gpio_flags(dev->of_node,
+					    "gpio", 0, &hpd_gpio_flags);
+	if (cec->gpio < 0)
+		return cec->gpio;
+
+	cec->irq = gpio_to_irq(cec->gpio);
+	gpio_direction_input(cec->gpio);
+	cec->dev = dev;
+
+	cec->adap = cec_pin_allocate_adapter(&cec_gpio_pin_ops,
+		cec, pdev->name, CEC_CAP_TRANSMIT | CEC_CAP_LOG_ADDRS |
+		CEC_CAP_PASSTHROUGH | CEC_CAP_RC | CEC_CAP_PHYS_ADDR |
+		CEC_CAP_MONITOR_ALL | CEC_CAP_MONITOR_PIN);
+	if (IS_ERR(cec->adap))
+		return PTR_ERR(cec->adap);
+
+	ret = cec_register_adapter(cec->adap, &pdev->dev);
+	if (ret) {
+		cec_delete_adapter(cec->adap);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, cec);
+	return 0;
+}
+
+static int cec_gpio_remove(struct platform_device *pdev)
+{
+	struct cec_gpio *cec = platform_get_drvdata(pdev);
+
+	cec_unregister_adapter(cec->adap);
+	return 0;
+}
+
+static const struct of_device_id cec_gpio_match[] = {
+	{
+		.compatible	= "cec-gpio",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, cec_gpio_match);
+
+static struct platform_driver cec_gpio_pdrv = {
+	.probe	= cec_gpio_probe,
+	.remove = cec_gpio_remove,
+	.driver = {
+		.name		= "cec-gpio",
+		.of_match_table	= cec_gpio_match,
+	},
+};
+
+module_platform_driver(cec_gpio_pdrv);
+
+MODULE_AUTHOR("Hans Verkuil <hans.verkuil@cisco.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("CEC GPIO driver");
-- 
2.13.2