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Subject: Re: [PATCH v4 1/2] platform: chrome: Add cros-usbpd-notify driver
To:     Prashant Malani <pmalani@chromium.org>
Cc:     Guenter Roeck <groeck@chromium.org>,
        Benson Leung <bleung@chromium.org>,
        Lee Jones <lee.jones@linaro.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Jon Flatley <jflat@chromium.org>,
        Gwendal Grignou <gwendal@chromium.org>
References: <20191220193843.47182-1-pmalani@chromium.org>
 <9bcb4671-f421-c639-f8c8-a02f62bfc7ee@collabora.com>
 <a632243b-92b0-20a3-3eff-9c7347e0e5bf@collabora.com>
 <CACeCKadvhhARxSWeb88Ny4BoRiy8opp+o0Zrzc-fQiRH6dH==A@mail.gmail.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <ab68d3e3-c33b-a0d1-6707-d1baafca1da7@collabora.com>
Date:   Mon, 13 Jan 2020 17:46:37 +0100
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Hi Prashant,

On 7/1/20 19:07, Prashant Malani wrote:
> Hi Enric,
> 
> On Sun, Dec 22, 2019 at 11:40 PM Enric Balletbo i Serra
> <enric.balletbo@collabora.com> wrote:
>>
>> Hi Prashant,
>>
>> On 23/12/19 8:18, Enric Balletbo i Serra wrote:
>>> Hi Prashant,
>>>
>>> On 20/12/19 20:38, Prashant Malani wrote:
>>>> From: Jon Flatley <jflat@chromium.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 non-ACPI platforms, the driver gets instantiated for ECs which
>>>> support the EC_FEATURE_USB_PD feature bit, and on such platforms, the
>>>> notification events will get delivered using the MKBP event handling
>>>> mechanism.
>>>>
>>>> Co-Developed-by: Prashant Malani <pmalani@chromium.org>
>>>> Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
>>>> Signed-off-by: Jon Flatley <jflat@chromium.org>
>>>> Signed-off-by: Prashant Malani <pmalani@chromium.org>
>>>
>>> For my own reference:
>>>
>>> Acked-for-chrome-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
>>>
>>
>> Sorry, too much rush acking this patch, here applies the same comment as patch 2
>>
>>>> ---
>>>>
>>>> Changes in v4(pmalani@chromium.org):
>>>> - No code changes, but added new version so that versioning is
>>>>   consistent with the next patch in the series.
>>>>
>>>> Changes in v3 (pmalani@chromium.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@chromium.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               |   9 ++
>>>>  drivers/platform/chrome/Makefile              |   1 +
>>>>  drivers/platform/chrome/cros_usbpd_notify.c   | 151 ++++++++++++++++++
>>>>  .../linux/platform_data/cros_usbpd_notify.h   |  17 ++
>>>>  4 files changed, 178 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..3a8a98f2fb4d1 100644
>>>> --- a/drivers/platform/chrome/Kconfig
>>>> +++ b/drivers/platform/chrome/Kconfig
>>>> @@ -226,6 +226,15 @@ 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
>>>> +    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 non-ACPI platforms this driver will get
>>>> +      initialized on ECs which support the feature EC_FEATURE_USB_PD.
>>>> +
>>>>  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..05a7db834d2e0
>>>> --- /dev/null
>>>> +++ b/drivers/platform/chrome/cros_usbpd_notify.c
>>>> @@ -0,0 +1,151 @@
>>>> +// SPDX-License-Identifier: GPL-2.0-only
>>>> +/*
>>>> + * Copyright 2019 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_commands.h>
>>>> +#include <linux/platform_data/cros_usbpd_notify.h>
>>>> +#include <linux/platform_data/cros_ec_proto.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
>>>> +
>>
>> For arm64 will follow this path, and this is not what we want, right?
> 
> (Following on from your latest email in Patch 2/2 in this series): I
> agree it would (follow this path) if arm64 defconfig enables ACPI in
> the mainline (side note: Chrome OS's kevin build leaves this config
> disabled).
> To ensure I make the right update to the patch, is the suggestion for
> this patch that we use #ifndef CONFIG_OF instead of #ifdef CONFIG_ACPI
> ?
> I think that may also be problematic since !CONFIG_OF doesn't
> necessarily imply CONFIG_ACPI.
> 
> Perhaps we should just make them two separate ifdef blocks, i.e #ifdef
> CONFIG_OF, and then #ifdef CONFIG_ACPI? Would be great to hear your
> recommendation here.
> 

If understand correctly what you want is on some devices (usually the ones that
use ACPI to instantiate the devices) use the notify ACPI callback, otherwise, on
devices using OF to instantiate the devices, create a notifier. The driver
should work on both cases. The problem is that CONFIG_OF and CONFIG_ACPI are not
 exclusive and select one does not imply not select the other. So yes I'm fine
on have both ifdef blocks, but in the cros_ec_dev (patch 2/2) you should
register the notifier only if IS_ENABLED(CONFIG_OF)

Cheers,
 Enric

> Thanks again!
>