Date:   Tue, 15 May 2018 09:25:45 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Hans Verkuil <hverkuil@...all.nl>, airlied@...ux.ie,
        hans.verkuil@...co.com, lee.jones@...aro.org, olof@...om.net,
        seanpaul@...gle.com
Cc:     sadolfsson@...gle.com, felixe@...gle.com, bleung@...gle.com,
        darekm@...gle.com, marcheu@...omium.org, fparent@...libre.com,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 5/5] media: platform: Add Chrome OS EC CEC driver

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@...libre.com>
>> ---
>>  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@...libre.com>
>> + */
>> +
>> +#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.

> 
>> +	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?
> 
>> +
>> +	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.

> 
>> +	} 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@...libre.com>");
>> +MODULE_LICENSE("GPL");
>> +MODULE_ALIAS("platform:" DRV_NAME);
>>
> 
> Regards,
> 
> 	Hans
> 

Thanks,
Neil

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