Date:   Mon, 27 Jan 2020 15:58:42 +0100
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Prashant Malani <pmalani@...omium.org>, groeck@...omium.org,
        bleung@...omium.org, lee.jones@...aro.org, sre@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Jon Flatley <jflat@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH v8 1/4] platform: chrome: Add cros-usbpd-notify driver

Hi Prashant,

On 25/1/20 0:18, Prashant Malani wrote:
> From: Jon Flatley <jflat@...omium.org>
> 
> ChromiumOS uses ACPI device with HID "GOOG0003" for power delivery
> related events. The existing cros-usbpd-charger driver relies on these
> events without ever actually receiving them on ACPI platforms. This is
> because in the ChromeOS kernel trees, the GOOG0003 device is owned by an
> ACPI driver that offers firmware updates to USB-C chargers.
> 
> Introduce a new platform driver under cros-ec, the ChromeOS embedded
> controller, that handles these PD events and dispatches them
> appropriately over a notifier chain to all drivers that use them.
> 
> On platforms that don't have the ACPI device defined, the driver gets
> instantiated for ECs which support the EC_FEATURE_USB_PD feature bit,
> and the notification events will get delivered using the MKBP event
> handling mechanism.
> 
> Co-Developed-by: Prashant Malani <pmalani@...omium.org>
> Reviewed-by: Gwendal Grignou <gwendal@...omium.org>
> Reviewed-by: Benson Leung <bleung@...omium.org>
> Signed-off-by: Jon Flatley <jflat@...omium.org>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
> 

Just a nit below but for my own reference:

Acked-for-chrome-platform: Enric Balletbo i Serra <enric.balletbo@...labora.com>

I am not sure if we're on time to get this merged on this merge window, though.

Thanks,
 Enric

> Changes in v8(pmalani@...omium.org):
> - Fix style nits.
> - Remove unrequired header.
> - Remove #ifdef CONFIG_OF dependency for platform driver registration.
> - Add module compile text to Kconfig help section.
> 
> Changes in v7(pmalani@...omium.org):
> - Removed use of module_platform_driver() and module_acpi_driver() since
>   that was causing redefinition compilation errors on arm64 defconfig.
>   Instead, explicitly defined the init and exit routines and
>   register/unregister the platform and ACPI drivers there.
> - Alphabetize #include header.
> 
> Changes in v6(pmalani@...omium.org):
> - Fix build error from typo in cros_usbpd_notify_acpi_device_ids
>   variable name.
> 
> Changes in v5(pmalani@...omium.org):
> - Split the driver into platform and ACPI variants, each enclosed by
>   CONFIG_OF and CONFIG_ACPI #ifdefs respectively.
> - Updated the copyright year to 2020.
> - Reworded the commit message and Kconfig description to incorporate
>   the modified driver structure.
> 
> Changes in v4(pmalani@...omium.org):
> - No code changes, but added new version so that versioning is
>   consistent with the next patch in the series.
> 
> Changes in v3 (pmalani@...omium.org):
> - Renamed driver and files from "cros_ec_pd_notify" to
>   "cros_usbpd_notify" to be more consistent with other naming.
> - Moved the change to include cros-usbpd-notify in the charger MFD
>   into a separate follow-on patch.
> 
> Changes in v2 (pmalani@...omium.org):
> - Removed dependency on DT entry; instead, we will instantiate
>   the driver on detecting EC_FEATURE_USB_PD for non-ACPI platforms.
> - Modified the cros-ec-pd-notify device to be an mfd_cell under
>   usbpdcharger for non-ACPI platforms. Altered the platform_probe() call
>   to derive the cros EC structs appropriately.
> - Replaced "usbpd_notify" with "pd_notify" in functions and structures.
> - Addressed comments from upstream maintainer.
> 
>  drivers/platform/chrome/Kconfig               |  13 ++
>  drivers/platform/chrome/Makefile              |   1 +
>  drivers/platform/chrome/cros_usbpd_notify.c   | 170 ++++++++++++++++++
>  .../linux/platform_data/cros_usbpd_notify.h   |  17 ++
>  4 files changed, 201 insertions(+)
>  create mode 100644 drivers/platform/chrome/cros_usbpd_notify.c
>  create mode 100644 include/linux/platform_data/cros_usbpd_notify.h
> 
> diff --git a/drivers/platform/chrome/Kconfig b/drivers/platform/chrome/Kconfig
> index 5f57282a28da0..e45e0fe057586 100644
> --- a/drivers/platform/chrome/Kconfig
> +++ b/drivers/platform/chrome/Kconfig
> @@ -226,6 +226,19 @@ config CROS_USBPD_LOGGER
>  	  To compile this driver as a module, choose M here: the
>  	  module will be called cros_usbpd_logger.
>  
> +config CROS_USBPD_NOTIFY
> +	tristate "ChromeOS Type-C power delivery event notifier"
> +	depends on CROS_EC

Like other cros-ec subdevices I am wondering if we should depend on
MFD_CROS_EC_DEV instead of CROS_EC (as doesn't really makes sense to only
depends on CROS_EC)

Also, like other cros-ec subdevices, we might be interested on have a:

       default MFD_CROS_EC_DEV

So it is selected when the cros-ec dev is configured by default.

Thanks,

 Enric

> +	help
> +	  If you say Y here, you get support for Type-C PD event notifications
> +	  from the ChromeOS EC. On ACPI platorms this driver will bind to the
> +	  GOOG0003 ACPI device, and on platforms which don't have this device it
> +	  will get initialized on ECs which support the feature
> +	  EC_FEATURE_USB_PD.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called cros_usbpd_notify.
> +
>  source "drivers/platform/chrome/wilco_ec/Kconfig"
>  
>  endif # CHROMEOS_PLATFORMS
> diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
> index aacd5920d8a18..f6465f8ef0b5e 100644
> --- a/drivers/platform/chrome/Makefile
> +++ b/drivers/platform/chrome/Makefile
> @@ -22,5 +22,6 @@ obj-$(CONFIG_CROS_EC_DEBUGFS)		+= cros_ec_debugfs.o
>  obj-$(CONFIG_CROS_EC_SENSORHUB)		+= cros_ec_sensorhub.o
>  obj-$(CONFIG_CROS_EC_SYSFS)		+= cros_ec_sysfs.o
>  obj-$(CONFIG_CROS_USBPD_LOGGER)		+= cros_usbpd_logger.o
> +obj-$(CONFIG_CROS_USBPD_NOTIFY)		+= cros_usbpd_notify.o
>  
>  obj-$(CONFIG_WILCO_EC)			+= wilco_ec/
> diff --git a/drivers/platform/chrome/cros_usbpd_notify.c b/drivers/platform/chrome/cros_usbpd_notify.c
> new file mode 100644
> index 0000000000000..6ead5c62b3c5f
> --- /dev/null
> +++ b/drivers/platform/chrome/cros_usbpd_notify.c
> @@ -0,0 +1,170 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2020 Google LLC
> + *
> + * This driver serves as the receiver of cros_ec PD host events.
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/module.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/platform_data/cros_ec_proto.h>
> +#include <linux/platform_data/cros_usbpd_notify.h>
> +#include <linux/platform_device.h>
> +
> +#define DRV_NAME "cros-usbpd-notify"
> +#define ACPI_DRV_NAME "GOOG0003"
> +
> +static BLOCKING_NOTIFIER_HEAD(cros_usbpd_notifier_list);
> +
> +/**
> + * cros_usbpd_register_notify - Register a notifier callback for PD events.
> + * @nb: Notifier block pointer to register
> + *
> + * On ACPI platforms this corresponds to host events on the ECPD
> + * "GOOG0003" ACPI device. On non-ACPI platforms this will filter mkbp events
> + * for USB PD events.
> + *
> + * Return: 0 on success or negative error code.
> + */
> +int cros_usbpd_register_notify(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&cros_usbpd_notifier_list,
> +						nb);
> +}
> +EXPORT_SYMBOL_GPL(cros_usbpd_register_notify);
> +
> +/**
> + * cros_usbpd_unregister_notify - Unregister notifier callback for PD events.
> + * @nb: Notifier block pointer to unregister
> + *
> + * Unregister a notifier callback that was previously registered with
> + * cros_usbpd_register_notify().
> + */
> +void cros_usbpd_unregister_notify(struct notifier_block *nb)
> +{
> +	blocking_notifier_chain_unregister(&cros_usbpd_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(cros_usbpd_unregister_notify);
> +
> +#ifdef CONFIG_ACPI
> +
> +static int cros_usbpd_notify_add_acpi(struct acpi_device *adev)
> +{
> +	return 0;
> +}
> +
> +static void cros_usbpd_notify_acpi(struct acpi_device *adev, u32 event)
> +{
> +	blocking_notifier_call_chain(&cros_usbpd_notifier_list, event, NULL);
> +}
> +
> +static const struct acpi_device_id cros_usbpd_notify_acpi_device_ids[] = {
> +	{ ACPI_DRV_NAME, 0 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, cros_usbpd_notify_acpi_device_ids);
> +
> +static struct acpi_driver cros_usbpd_notify_acpi_driver = {
> +	.name = DRV_NAME,
> +	.class = DRV_NAME,
> +	.ids = cros_usbpd_notify_acpi_device_ids,
> +	.ops = {
> +		.add = cros_usbpd_notify_add_acpi,
> +		.notify = cros_usbpd_notify_acpi,
> +	},
> +};
> +
> +#endif /* CONFIG_ACPI */
> +
> +static int cros_usbpd_notify_plat(struct notifier_block *nb,
> +				  unsigned long queued_during_suspend,
> +				  void *data)
> +{
> +	struct cros_ec_device *ec_dev = (struct cros_ec_device *)data;
> +	u32 host_event = cros_ec_get_host_event(ec_dev);
> +
> +	if (!host_event)
> +		return NOTIFY_BAD;
> +
> +	if (host_event & EC_HOST_EVENT_MASK(EC_HOST_EVENT_PD_MCU)) {
> +		blocking_notifier_call_chain(&cros_usbpd_notifier_list,
> +					     host_event, NULL);
> +		return NOTIFY_OK;
> +	}
> +	return NOTIFY_DONE;
> +}
> +
> +static int cros_usbpd_notify_probe_plat(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct cros_ec_dev *ecdev = dev_get_drvdata(dev->parent);
> +	struct notifier_block *nb;
> +	int ret;
> +
> +	nb = devm_kzalloc(dev, sizeof(*nb), GFP_KERNEL);
> +	if (!nb)
> +		return -ENOMEM;
> +
> +	nb->notifier_call = cros_usbpd_notify_plat;
> +	dev_set_drvdata(dev, nb);
> +
> +	ret = blocking_notifier_chain_register(&ecdev->ec_dev->event_notifier,
> +					       nb);
> +	if (ret < 0) {
> +		dev_err(dev, "Failed to register notifier\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cros_usbpd_notify_remove_plat(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct cros_ec_dev *ecdev = dev_get_drvdata(dev->parent);
> +	struct notifier_block *nb =
> +		(struct notifier_block *)dev_get_drvdata(dev);
> +
> +	blocking_notifier_chain_unregister(&ecdev->ec_dev->event_notifier, nb);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cros_usbpd_notify_plat_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +	},
> +	.probe = cros_usbpd_notify_probe_plat,
> +	.remove = cros_usbpd_notify_remove_plat,
> +};
> +
> +static int __init cros_usbpd_notify_init(void)
> +{
> +	int ret;
> +
> +	ret = platform_driver_register(&cros_usbpd_notify_plat_driver);
> +	if (ret < 0)
> +		return ret;
> +
> +#ifdef CONFIG_ACPI
> +	acpi_bus_register_driver(&cros_usbpd_notify_acpi_driver);
> +#endif
> +	return 0;
> +}
> +
> +static void __exit cros_usbpd_notify_exit(void)
> +{
> +#ifdef CONFIG_ACPI
> +	acpi_bus_unregister_driver(&cros_usbpd_notify_acpi_driver);
> +#endif
> +	platform_driver_unregister(&cros_usbpd_notify_plat_driver);
> +}
> +
> +module_init(cros_usbpd_notify_init);
> +module_exit(cros_usbpd_notify_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("ChromeOS power delivery notifier device");
> +MODULE_AUTHOR("Jon Flatley <jflat@...omium.org>");
> +MODULE_ALIAS("platform:" DRV_NAME);
> diff --git a/include/linux/platform_data/cros_usbpd_notify.h b/include/linux/platform_data/cros_usbpd_notify.h
> new file mode 100644
> index 0000000000000..4f2791722b6d3
> --- /dev/null
> +++ b/include/linux/platform_data/cros_usbpd_notify.h
> @@ -0,0 +1,17 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * ChromeOS EC Power Delivery Notifier Driver
> + *
> + * Copyright 2020 Google LLC
> + */
> +
> +#ifndef __LINUX_PLATFORM_DATA_CROS_USBPD_NOTIFY_H
> +#define __LINUX_PLATFORM_DATA_CROS_USBPD_NOTIFY_H
> +
> +#include <linux/notifier.h>
> +
> +int cros_usbpd_register_notify(struct notifier_block *nb);
> +
> +void cros_usbpd_unregister_notify(struct notifier_block *nb);
> +
> +#endif  /* __LINUX_PLATFORM_DATA_CROS_USBPD_NOTIFY_H */
> 

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