linux-kernel - Re: [PATCH v4 2/2] mfd: cros_ec: Add cros-usbpd-notify subdevice

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Message-ID: <CACeCKadAJE-ayisXOib4ZV9_BDORp-dpoT_KSMnJj3Y30dF_6A@mail.gmail.com>
Date:   Thu, 2 Jan 2020 15:52:24 -0800
From:   Prashant Malani <pmalani@...omium.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Guenter Roeck <groeck@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Lee Jones <lee.jones@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] mfd: cros_ec: Add cros-usbpd-notify subdevice

Hi Enric,


On Mon, Dec 23, 2019 at 12:29 PM Prashant Malani <pmalani@...omium.org> wrote:
>
> Hi Enric,
>
> On Sun, Dec 22, 2019 at 11:25 PM Enric Balletbo i Serra
> <enric.balletbo@...labora.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@...omium.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?

>
> 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.
> > >