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Subject: Re: [PATCH v4 2/2] mfd: cros_ec: Add cros-usbpd-notify subdevice
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>
References: <20191220193843.47182-1-pmalani@chromium.org>
 <20191220193843.47182-2-pmalani@chromium.org>
 <7eecafb2-4686-b448-2837-4181188365b1@collabora.com>
 <CACeCKadFKWUNHHT-vs686Sz2-CcD0kNeUgqkJT5Q2ATji4L58w@mail.gmail.com>
 <CACeCKadAJE-ayisXOib4ZV9_BDORp-dpoT_KSMnJj3Y30dF_6A@mail.gmail.com>
From:   Enric Balletbo i Serra <enric.balletbo@collabora.com>
Message-ID: <d825c0ec-8fbd-b23b-2125-bdfccb623dd7@collabora.com>
Date:   Tue, 7 Jan 2020 17:51:09 +0100
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Hi Prashant,

On 3/1/20 0:52, Prashant Malani wrote:
> Hi Enric,
> 
> 
> On Mon, Dec 23, 2019 at 12:29 PM Prashant Malani <pmalani@chromium.org> wrote:
>>
>> Hi Enric,
>>
>> On Sun, Dec 22, 2019 at 11:25 PM Enric Balletbo i Serra
>> <enric.balletbo@collabora.com> wrote:
>>>
>>> Hi Prashant,
>>>
>>> On 20/12/19 20:38, Prashant Malani wrote:
>>>> Add the cros-usbpd-notify driver as a subdevice on non-ACPI platforms
>>>> that support the EC_FEATURE_USB_PD EC feature flag.
>>>>
>>>> This driver allows other cros-ec devices to receive PD event
>>>> notifications from the Chrome OS Embedded Controller (EC) via a
>>>> notification chain.
>>>>
>>>> Signed-off-by: Prashant Malani <pmalani@chromium.org>
>>>> ---
>>>>
>>>> Changes in v4:
>>>> - Removed #ifndef usage; instead, moved cros-usbpd-notify to a separate
>>>>   mfd_cell and used an IS_ENABLED() check.
>>>> - Changed commit title and description slightly to reflect change in
>>>>   code.
>>>>
>>>>  drivers/mfd/cros_ec_dev.c | 21 +++++++++++++++++++++
>>>>  1 file changed, 21 insertions(+)
>>>>
>>>> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
>>>> index c4b977a5dd966..da198abe2b0a6 100644
>>>> --- a/drivers/mfd/cros_ec_dev.c
>>>> +++ b/drivers/mfd/cros_ec_dev.c
>>>> @@ -5,6 +5,7 @@
>>>>   * Copyright (C) 2014 Google, Inc.
>>>>   */
>>>>
>>>> +#include <linux/kconfig.h>
>>>>  #include <linux/mfd/core.h>
>>>>  #include <linux/mfd/cros_ec.h>
>>>>  #include <linux/module.h>
>>>> @@ -87,6 +88,10 @@ static const struct mfd_cell cros_usbpd_charger_cells[] = {
>>>>       { .name = "cros-usbpd-logger", },
>>>>  };
>>>>
>>>> +static const struct mfd_cell cros_usbpd_notify_cells[] = {
>>>> +     { .name = "cros-usbpd-notify", },
>>>> +};
>>>> +
>>>>  static const struct cros_feature_to_cells cros_subdevices[] = {
>>>>       {
>>>>               .id             = EC_FEATURE_CEC,
>>>> @@ -202,6 +207,22 @@ static int ec_device_probe(struct platform_device *pdev)
>>>>               }
>>>>       }
>>>>
>>>> +     /*
>>>> +      * The PD notifier driver cell is separate since it only needs to be
>>>> +      * explicitly added on non-ACPI platforms.
>>>
>>>
>>> Sorry to not catch this before, but a worry arose. Is non-ACPI platforms or
>>> non-X86 platforms or on OF platforms?
>>>
>>> ARM64 for example has the CONFIG_ACPI symbol set to yes, with the below
>>> condition condition will not work on Kevin for example and IIUC this is not what
>>> we want, I think we want IS_ENABLED(CONFIG_OF)?
>> Thanks for noting this. I will check with a kevin, and with the
>> internal build flags to verify whether there are ARM64 which have the
>> GOOG0003 PD notification device.
>> I'll update this thread with my findings.
> AFAICT from the Chrome OS kernel build step .config output, kevin
> doesn't have CONFIG_ACPI enabled (it is marked as "# CONFIG_ACPI is
> not set"), and it doesn't look like there are Chrome OS ARM devices
> that use ACPI (I believe it's only used on Chrome OS x86-based
> devices). So perhaps it is not a concern?
> 

The problem is, although it is not used in your configs, it can be selected, and
fwiw some defconfigs in mainline have it enabled, i.e the arm64 defconfig.

I think you're testing the patch on x86 but I suspect we want also the notifier
on some arm64 platforms (like kevin) right? In such case I won't get the
notifier because CONFIG_OF and CONFIG_ACPI is enabled on my defconfig.

My guess is that the logic should be if IS_ENABLED(CONFIG_OF) call
cros_ec_check_features, otherwise ACPI will do the magic instead of
(!IS_ENABLED(CONFIG_ACPI))

Best,
 Enric

>>
>> Best,
>>
>>>
>>> Thanks,
>>>  Enric
>>>
>>>> +      */
>>>> +     if (!IS_ENABLED(CONFIG_ACPI)) {
>>>> +             if (cros_ec_check_features(ec, EC_FEATURE_USB_PD)) {
>>>> +                     retval = mfd_add_hotplug_devices(ec->dev,
>>>> +                                     cros_usbpd_notify_cells,
>>>> +                                     ARRAY_SIZE(cros_usbpd_notify_cells));
>>>> +                     if (retval)
>>>> +                             dev_err(ec->dev,
>>>> +                                     "failed to add PD notify devices: %d\n",
>>>> +                                     retval);
>>>> +             }
>>>> +     }
>>>> +
>>>>       /*
>>>>        * The following subdevices cannot be detected by sending the
>>>>        * EC_FEATURE_GET_CMD to the Embedded Controller device.
>>>>