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

[Hans Verkuil]

On 05/15/18 09:25, Neil Armstrong wrote:
> Hi Hans,
> 
> Thanks for the extensive review.
> 
> On 15/05/2018 08:58, Hans Verkuil wrote:
>> 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.
> 
> Oops, I forgot to remove this phrase, the FW will maybe support it, but it has been
> dropped for the first revision.
> 
>>
>>>
>>> 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.
> 
> I will definitely setup this kind of system, I tried using am Amlogic SoC, but it really can't monitor the bus....
> 
> But I also have an ST STM32F0 Development board with double HDMI connector to develop CEC, I'll maybe try to use it for that purpose.

You really want a setup that uses the cec-gpio driver since that allows
you to do CEC error injection. If you can hook up the CEC pin to a GPIO
on the stm32 board, than that should work just as well as with the RPi3.

> 
>>
>>> +	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.
> 
> Ok, we were unsure about this, thanks for the clarification.
> 
>>
>>> +}
>>> +
>>> +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?

Did you miss this comment? It's weird what is happening here.

>>
>>> +
>>> +	memset(&msg, 0, sizeof(msg));
>>
>> and you can drop this memset.
> 
> I always forget this trick.
> 
>>
>>> +	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.
> 
> Forgor to remove it, the API changed in the meantime, now it 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.
> 
> I will change with you comment, looks way cleaner.
> 
>>
>>> +			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?
> 
> No, Yes, the EC FW is independent of the HPD status
> 
>>
>>> +	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.
> 
> It's in case an HW having a CEC capable FW but not in the cec_dmi_match_table, in this case
> it won't fail but still enable the CEC interface without a notifier.

I don't think that's a good idea. CAP_PHYS_ADDR should *only* be used in situations
where it is truly impossible to tell which output is connected to the CEC adapter.
That's the case with e.g. USB CEC dongles where you have no idea how the user
connected the HDMI cables.

But I assume that in this case it just means that the cec_dmi_match_table needs
to be updated, i.e. it is a driver bug.

Another thing: this driver assumes that there is only one CEC adapter for only
one HDMI output. But what if there are more HDMI outputs? Will there be one
CEC adapter for each output? Or does the hardware have no provisions for that?

Something should be mentioned about this in a comment.

Regards,

	Hans

> 
>>
>>> +	} 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.
> 
> Noted.
> 
>>
>>> +
>>> +	/* 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
>>
> 
> Thanks,
> Neil
>