Re: [RFC PATCH 5/5] media: platform: Add Chrome OS EC CEC driver

[Hans Verkuil]

On 05/15/2018 12:40 AM, Neil Armstrong wrote:
> The Chrome OS Embedded Controller can expose a CEC bus, this patch add the
> driver for such feature of the Embedded Controller.
> 
> This driver is part of the cros-ec MFD and will be add as a sub-device when
> the feature bit is exposed by the EC.
> 
> The controller will only handle a single logical address and handles
> all the messages retries and will only expose Success or Error.
> 
> When the logical address is invalid, the controller will act as a CEC sniffer
> and transfer all messages on the bus.

I did not see any support for this. If this works as you state here, then adding
support for CEC_CAP_MONITOR_ALL is highly recommended.

> 
> Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> ---
>  drivers/media/platform/Kconfig               |  11 +
>  drivers/media/platform/Makefile              |   2 +
>  drivers/media/platform/cros-ec/Makefile      |   1 +
>  drivers/media/platform/cros-ec/cros-ec-cec.c | 331 +++++++++++++++++++++++++++
>  4 files changed, 345 insertions(+)
>  create mode 100644 drivers/media/platform/cros-ec/Makefile
>  create mode 100644 drivers/media/platform/cros-ec/cros-ec-cec.c

Shouldn't the directory be called cros-ec-cec?

> 
> diff --git a/drivers/media/platform/Kconfig b/drivers/media/platform/Kconfig
> index c7a1cf8..e55a8ed2 100644
> --- a/drivers/media/platform/Kconfig
> +++ b/drivers/media/platform/Kconfig
> @@ -546,6 +546,17 @@ menuconfig CEC_PLATFORM_DRIVERS
>  
>  if CEC_PLATFORM_DRIVERS
>  
> +config VIDEO_CROS_EC_CEC
> +	tristate "Chrome OS EC CEC driver"
> +	depends on MFD_CROS_EC || COMPILE_TEST
> +	select CEC_CORE
> +	select CEC_NOTIFIER
> +	---help---
> +	  If you say yes here you will get support for the
> +	  Chrome OS Embedded Controller's CEC.
> +	  The CEC bus is present in the HDMI connector and enables communication
> +	  between compatible devices.
> +
>  config VIDEO_MESON_AO_CEC
>  	tristate "Amlogic Meson AO CEC driver"
>  	depends on ARCH_MESON || COMPILE_TEST
> diff --git a/drivers/media/platform/Makefile b/drivers/media/platform/Makefile
> index 932515d..0e0582e 100644
> --- a/drivers/media/platform/Makefile
> +++ b/drivers/media/platform/Makefile
> @@ -92,3 +92,5 @@ obj-$(CONFIG_VIDEO_QCOM_CAMSS)		+= qcom/camss-8x16/
>  obj-$(CONFIG_VIDEO_QCOM_VENUS)		+= qcom/venus/
>  
>  obj-y					+= meson/
> +
> +obj-y					+= cros-ec/
> diff --git a/drivers/media/platform/cros-ec/Makefile b/drivers/media/platform/cros-ec/Makefile
> new file mode 100644
> index 0000000..9ce97f9
> --- /dev/null
> +++ b/drivers/media/platform/cros-ec/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_VIDEO_CROS_EC_CEC) += cros-ec-cec.o
> diff --git a/drivers/media/platform/cros-ec/cros-ec-cec.c b/drivers/media/platform/cros-ec/cros-ec-cec.c
> new file mode 100644
> index 0000000..fea90da
> --- /dev/null
> +++ b/drivers/media/platform/cros-ec/cros-ec-cec.c
> @@ -0,0 +1,331 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * CEC driver for Chrome OS Embedded Controller
> + *
> + * Copyright (c) 2018 BayLibre, SAS
> + * Author: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/dmi.h>
> +#include <linux/cec.h>
> +#include <linux/slab.h>
> +#include <linux/interrupt.h>
> +#include <media/cec.h>
> +#include <media/cec-notifier.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/mfd/cros_ec_commands.h>
> +
> +#define DRV_NAME	"cros-ec-cec"
> +
> +/**
> + * struct cros_ec_cec - Driver data for EC CEC
> + *
> + * @cros_ec: Pointer to EC device
> + * @notifier: Notifier info for responding to EC events
> + * @adap: CEC adapter
> + * @notify: CEC notifier pointer
> + * @rc_msg: storage for a received message
> + */
> +struct cros_ec_cec {
> +	struct cros_ec_device *cros_ec;
> +	struct notifier_block notifier;
> +	struct cec_adapter *adap;
> +	struct cec_notifier *notify;
> +	struct cec_msg rx_msg;
> +};
> +
> +static void handle_cec_message(struct cros_ec_cec *cros_ec_cec)
> +{
> +	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> +	uint8_t *cec_message = cros_ec->event_data.data.cec_message;
> +	unsigned int len = cros_ec->event_size;
> +
> +	cros_ec_cec->rx_msg.len = len;

How robust is the underlying code and hardware? What happens if a
CEC message with more than 16 bytes is received?

Hard to test unless you have an RPi3 set up as a CEC debugger. See
last section in https://hverkuil.home.xs4all.nl/cec-status.txt.

Since you worked with CEC for a while now I recommend you set up such
a system. It's cheap and very useful.

> +	memcpy(cros_ec_cec->rx_msg.msg, cec_message, len);
> +
> +	cec_received_msg(cros_ec_cec->adap, &cros_ec_cec->rx_msg);
> +}
> +
> +static void handle_cec_event(struct cros_ec_cec *cros_ec_cec)
> +{
> +	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> +	uint32_t events = cros_ec->event_data.data.cec_events;
> +
> +	if (events & EC_MKBP_CEC_SEND_OK)
> +		cec_transmit_attempt_done(cros_ec_cec->adap,
> +					  CEC_TX_STATUS_OK);
> +
> +	if (events & EC_MKBP_CEC_SEND_FAILED)
> +		cec_transmit_attempt_done(cros_ec_cec->adap,
> +					  CEC_TX_STATUS_ERROR);

You said above that the HW takes care of all the message retries.
If that's the case, then you need to use cec_transmit_done here
and pass in status CEC_TX_STATUS_MAX_RETRIES | CEC_TX_STATUS_NACK.
The MAX_RETRIES flag tells the cec core that it shouldn't attempt
to retry the message because the HW already did that.

NACK is better than ERROR if the hardware supports only an OK/FAIL
result.

> +}
> +
> +static int cros_ec_cec_event(struct notifier_block *nb,
> +	unsigned long queued_during_suspend, void *_notify)
> +{
> +	struct cros_ec_cec *cros_ec_cec;
> +	struct cros_ec_device *cros_ec;
> +
> +	cros_ec_cec = container_of(nb, struct cros_ec_cec, notifier);
> +	cros_ec = cros_ec_cec->cros_ec;
> +
> +	if (cros_ec->event_data.event_type == EC_MKBP_CEC_EVENT) {
> +		handle_cec_event(cros_ec_cec);
> +		return NOTIFY_OK;
> +	}
> +
> +	if (cros_ec->event_data.event_type == EC_MKBP_EVENT_CEC_MESSAGE) {
> +		handle_cec_message(cros_ec_cec);
> +		return NOTIFY_OK;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int cros_ec_cec_set_log_addr(struct cec_adapter *adap, u8 logical_addr)
> +{
> +	struct cros_ec_cec *cros_ec_cec = adap->priv;
> +	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> +	struct {
> +		struct cros_ec_command msg;
> +		struct ec_params_cec_set data;
> +	} __packed msg;

Just say: ... msg = {};

> +	int ret = 0;
> +
> +	if (logical_addr == CEC_LOG_ADDR_INVALID)
> +		return 0;

This looks weird. If I had configured a LA before, then this should unconfigure
it. But it just keeps the existing LA, so any poll messages to us will still
be Acked. Or am I missing something?

> +
> +	memset(&msg, 0, sizeof(msg));

and you can drop this memset.

> +	msg.msg.command = EC_CMD_CEC_SET;
> +	msg.msg.outsize = sizeof(msg.data);
> +	msg.data.cmd = CEC_CMD_LOGICAL_ADDRESS;
> +	msg.data.address = logical_addr;
> +
> +	ret = cros_ec_cmd_xfer_status(cros_ec, &msg.msg);
> +	if (ret < 0) {
> +		dev_err(cros_ec->dev,
> +			"error setting CEC logical address on EC: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cros_ec_cec_transmit(struct cec_adapter *adap, u8 attempts,
> +				u32 signal_free_time, struct cec_msg *cec_msg)
> +{
> +	struct cros_ec_cec *cros_ec_cec = adap->priv;
> +	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> +	struct {
> +		struct cros_ec_command msg;
> +		struct ec_params_cec_write data;
> +	} __packed msg;

... msg = {};

> +	int ret = 0;
> +
> +	if (cec_msg->len > MAX_CEC_MSG_LEN)
> +		return -EINVAL;

No need, can never happen.

> +
> +	memset(&msg, 0, sizeof(msg));

and drop this.

> +	msg.msg.command = EC_CMD_CEC_WRITE_MSG;
> +	msg.msg.outsize = cec_msg->len;
> +	memcpy(msg.data.msg, cec_msg->msg, cec_msg->len);
> +
> +	ret = cros_ec_cmd_xfer_status(cros_ec, &msg.msg);
> +	if (ret < 0) {
> +		dev_err(cros_ec->dev,
> +			"error writting CEC msg on EC: %d\n", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cros_ec_cec_adap_enable(struct cec_adapter *adap, bool enable)
> +{
> +	struct cros_ec_cec *cros_ec_cec = adap->priv;
> +	struct cros_ec_device *cros_ec = cros_ec_cec->cros_ec;
> +	struct {
> +		struct cros_ec_command msg;
> +		struct ec_params_cec_set data;
> +	} __packed msg;
> +	int ret = 0;
> +
> +	memset(&msg, 0, sizeof(msg));
> +	msg.msg.command = EC_CMD_CEC_SET;
> +	msg.msg.outsize = sizeof(msg.data);
> +	msg.data.cmd = CEC_CMD_ENABLE;
> +	msg.data.enable = enable;
> +
> +	ret = cros_ec_cmd_xfer_status(cros_ec, &msg.msg);
> +	if (ret < 0) {
> +		dev_err(cros_ec->dev,
> +			"error %sabling CEC on EC: %d\n",
> +			(enable ? "en" : "dis"), ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct cec_adap_ops cros_ec_cec_ops = {
> +	.adap_enable = cros_ec_cec_adap_enable,
> +	.adap_log_addr = cros_ec_cec_set_log_addr,
> +	.adap_transmit = cros_ec_cec_transmit,
> +};
> +
> +#ifdef CONFIG_PM_SLEEP
> +static int cros_ec_cec_suspend(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct cros_ec_cec *cros_ec_cec = dev_get_drvdata(&pdev->dev);
> +
> +	if (device_may_wakeup(dev))
> +		enable_irq_wake(cros_ec_cec->cros_ec->irq);
> +
> +	return 0;
> +}
> +
> +static int cros_ec_cec_resume(struct device *dev)
> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct cros_ec_cec *cros_ec_cec = dev_get_drvdata(&pdev->dev);
> +
> +	if (device_may_wakeup(dev))
> +		disable_irq_wake(cros_ec_cec->cros_ec->irq);
> +
> +	return 0;
> +}
> +#endif
> +
> +static SIMPLE_DEV_PM_OPS(cros_ec_cec_pm_ops,
> +	cros_ec_cec_suspend, cros_ec_cec_resume);
> +
> +
> +struct cec_dmi_match {
> +	char *sys_vendor;
> +	char *product_name;
> +	char *devname;
> +	char *conn;
> +};
> +
> +static const struct cec_dmi_match cec_dmi_match_table[] = {
> +	/* Google Fizz */
> +	{ "Google", "Fizz", "0000:00:02.0", "HDMI-A-1" },
> +};
> +
> +static int cros_ec_cec_get_notifier(struct cec_notifier **notify)
> +{
> +	int i;
> +
> +	for (i = 0 ; i < ARRAY_SIZE(cec_dmi_match_table) ; ++i) {
> +		const struct cec_dmi_match *m = &cec_dmi_match_table[i];
> +
> +		if (dmi_match(DMI_SYS_VENDOR, m->sys_vendor) &&
> +		    dmi_match(DMI_PRODUCT_NAME, m->product_name)) {
> +			*notify = cec_notifier_get_byname(m->devname, m->conn);

See my comments for patch 2/5.

> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +static int cros_ec_cec_probe(struct platform_device *pdev)
> +{
> +	struct cros_ec_dev *ec_dev = dev_get_drvdata(pdev->dev.parent);
> +	struct cros_ec_device *cros_ec = ec_dev->ec_dev;
> +	struct cros_ec_cec *cros_ec_cec;
> +	unsigned int cec_caps = CEC_CAP_DEFAULTS;

Does this need CEC_CAP_NEEDS_HPD? Can it still use CEC if there is no HPD
signal?

> +	int ret;
> +
> +	cros_ec_cec = devm_kzalloc(&pdev->dev, sizeof(*cros_ec_cec),
> +				   GFP_KERNEL);
> +	if (!cros_ec_cec)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, cros_ec_cec);
> +	cros_ec_cec->cros_ec = cros_ec;
> +
> +	ret = cros_ec_cec_get_notifier(&cros_ec_cec->notify);
> +	if (ret) {
> +		dev_warn(&pdev->dev, "no CEC notifier available\n");
> +		cec_caps |= CEC_CAP_PHYS_ADDR;

Can this happen? What hardware has this? I am strongly opposed to CEC drivers
using this capability unless there is no other option. It's a pain for userspace.

> +	} else if (!cros_ec_cec->notify) {
> +		return -EPROBE_DEFER;
> +	}
> +
> +	ret = device_init_wakeup(&pdev->dev, 1);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to initialize wakeup\n");
> +		return ret;
> +	}
> +
> +	cros_ec_cec->adap = cec_allocate_adapter(&cros_ec_cec_ops, cros_ec_cec,
> +						 DRV_NAME, cec_caps, 1);
> +	if (IS_ERR(cros_ec_cec->adap))
> +		return PTR_ERR(cros_ec_cec->adap);
> +
> +	cros_ec_cec->adap->owner = THIS_MODULE;

This can be dropped, cec_register_adapter() sets this already.

> +
> +	/* Get CEC events from the EC. */
> +	cros_ec_cec->notifier.notifier_call = cros_ec_cec_event;
> +	ret = blocking_notifier_chain_register(&cros_ec->event_notifier,
> +					       &cros_ec_cec->notifier);
> +	if (ret) {
> +		dev_err(&pdev->dev, "failed to register notifier\n");
> +		cec_delete_adapter(cros_ec_cec->adap);
> +		return ret;
> +	}
> +
> +	ret = cec_register_adapter(cros_ec_cec->adap, &pdev->dev);
> +	if (ret < 0) {
> +		cec_delete_adapter(cros_ec_cec->adap);
> +		return ret;
> +	}
> +
> +	cec_register_cec_notifier(cros_ec_cec->adap, cros_ec_cec->notify);
> +
> +	return 0;
> +}
> +
> +static int cros_ec_cec_remove(struct platform_device *pdev)
> +{
> +	struct cros_ec_cec *cros_ec_cec = platform_get_drvdata(pdev);
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	ret = blocking_notifier_chain_unregister(
> +			&cros_ec_cec->cros_ec->event_notifier,
> +			&cros_ec_cec->notifier);
> +
> +	if (ret) {
> +		dev_err(dev, "failed to unregister notifier\n");
> +		return ret;
> +	}
> +
> +	cec_unregister_adapter(cros_ec_cec->adap);
> +
> +	if (cros_ec_cec->notify)
> +		cec_notifier_put(cros_ec_cec->notify);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cros_ec_cec_driver = {
> +	.probe = cros_ec_cec_probe,
> +	.remove  = cros_ec_cec_remove,
> +	.driver = {
> +		.name = DRV_NAME,
> +		.pm = &cros_ec_cec_pm_ops,
> +	},
> +};
> +
> +module_platform_driver(cros_ec_cec_driver);
> +
> +MODULE_DESCRIPTION("CEC driver for Chrome OS ECs");
> +MODULE_AUTHOR("Neil Armstrong <narmstrong@xxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:" DRV_NAME);
> 

Regards,

	Hans