Date:   Tue, 21 Jan 2020 13:17:12 -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>, sre@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pm@...r.kernel.org, Jon Flatley <jflat@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>
Subject: Re: [PATCH v7 1/3] platform: chrome: Add cros-usbpd-notify driver

Hi Enric,

Thanks for the recommendations; Please see some notes inline:
On Tue, Jan 21, 2020 at 4:10 AM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> Hi Prashant,
>
> Sorry, I am still having issues with this patch. It doesn't work as expected on
> my Samsung Chromebook Plus because the below code tries to register twice the
> driver and then hangs for some reason.
>
>   [    9.381368] Error: Driver 'cros-usbpd-notify' is already registered,
> aborting...
Hmm, is this because platform_driver_register and
acpi_bus_driver_register both try to register a device with the same
name?
If so, we could simply rename the drivers (cros-usbpd-notify-platform
and cros-usbpd-notify-acpi) and then we don't have to make any other
modifications?
>
> Also I have the problem that I don't have any x86 device using the
> cros_usbpd_charger so I can't really test for x86.
>
> Let me propose some changes and let's see if it works for you.
>
> On 17/1/20 1:28, Prashant Malani wrote:
> > From: Jon Flatley <jflat@...omium.org>
> > @@ -226,6 +226,16 @@ 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 platforms which don't have this device it
>
> Please use a max length of 80 characters.
My text editor says that it is 80 chars, but I will verify it again.
>
> > +       will get initialized on ECs which support the feature
> > +       EC_FEATURE_USB_PD.
> > +
>
> Please add:
>
>           To compile this driver as a module, choose M here: the
>           module will be called cros_usbpd_notify.
>
> So checkpatch --strict is more happy.
Done
>
> >  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..4705164e38bf4
> > --- /dev/null
> > +++ b/drivers/platform/chrome/cros_usbpd_notify.c
> > @@ -0,0 +1,180 @@
> > +// 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_commands.h>
>
> I think this include is not needed.
Done
>
> > +#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);
> > +
> > +
>
> Please don't use multiple blank lines
Sorry, done.
>
> > +/**
> > + * 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 */
> > +
> > +#ifdef CONFIG_OF
> > +
>
> I propose to remove this ...
>
> > +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;
> > +
>
> What about this?
>
> +       /*
> +        * We only need to register the notifier if we are really using
> +        * device-tree, otherwise, for ACPI case it will register an
> +        * acpi_driver and use the .notify callback.
> +        */
> +       if (IS_ENABLED(CONFIG_OF) && !dev->of_node)
> +               return 0;
> +
If we add your proposed check in cros_ec_dev.c, do we need this check
here? It seems like both check the same thing, i.e only go ahead and
initialize the module and add the device if "IS_ENABLED(CONFIG_OF) &&
dev->of_node" is true.
Also, kindly see my note further down regarding of_node
("dev->of_node" evaluates to false even for the DT case on the ARM
builds I am testing with)
>
> > +     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);
> > +
>
> Only unregister for the device-tree case
>
> +       if (IS_ENABLED(CONFIG_OF) && dev->of_node)
Same as above; is this required if we check for of_node in cros_ec_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,
> > +};
> > +
> > +#endif /* CONFIG_OF */
> > +
> > +static int __init cros_usbpd_notify_init(void)
> > +{
> > +     int ret = 0;
> > +#ifdef CONFIG_OF
> > +     ret = platform_driver_register(&cros_usbpd_notify_plat_driver);
> > +     if (ret != 0)
> > +             pr_err("cros-usbpd-notify platform driver register failed.\n");
> > +#endif
>
>
> To simplify the ifdery, let's register the platform driver always, it'll be noop
> in ACPI case.
>
>         int ret;
>
>         ret = platform_driver_register(&cros_usbpd_notify_driver);
>         if (ret < 0)
>                 return ret;
>
>
> > +#ifdef CONFIG_ACPI
> > +     ret = acpi_bus_register_driver(&cros_usbpd_notify_acpi_driver);
> > +     if (ret != 0)
> > +             pr_err("cros-usbpd-notify ACPI driver register failed.\n");
> > +#endif
> > +     return ret;
We should return 0 here, correct?
>
> And register the ACPI driver if CONFIG_ACPI is enabled, note that the error is
> ignored because that call will fail on device-tree based devices with
> CONFIG_ACPI enabled.

My initial thought was that this would fail for the case where we have
CONFIG_ACPI && actually use an ACPI device (like newer x86
Chromebooks), because the acpi_bus_register_driver() would fail, since
the platform driver was already registered.
However, on testing with CONFIG_ACPI && !CONFIG_OF on a system which
has the GOOG0003 device, I see the "notify" call being invoked
successfully, so this works.
>
> +#ifdef CONFIG_ACPI
> +       acpi_bus_unregister_driver(&cros_usbpd_notify_acpi_driver)
> +#endif
Just checking, the above edit is not needed here, right? Sounds like
it's a duplicate of what you added in _exit().
>
> > +}
> > +
> > +static void __exit cros_usbpd_notify_exit(void)
> > +{
> > +#ifdef CONFIG_OF
> > +     platform_driver_unregister(&cros_usbpd_notify_plat_driver);
> > +#endif
> > +#ifdef CONFIG_ACPI
> > +     acpi_bus_unregister_driver(&cros_usbpd_notify_acpi_driver);
> > +#endif
>
> And for the remove, only unregister the acpi driver if CONFIG_ACPI is enabled.
Done.
>
> +#ifdef CONFIG_ACPI
> +       acpi_bus_unregister_driver(&cros_usbpd_notify_acpi_driver);
> +#endif
> +       platform_driver_unregister(&cros_usbpd_notify_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);
>
>
> Double check that the code builds with different CONFIG options. I didn't check
> the ifery involved.
>
>   CONFIG_ACPI && CONFIG_OF
>   CONFIG_ACPI && !CONFIG_OF
>   !CONFIG_ACPI && CONFIG_OF
>
> And we need to _make sure_ that the platform driver is _only_ instantiated via
> cros_ec_dev when we are really under a device-tree based device, so the check
> probably should be something like this:
>
>
> diff --git a/drivers/mfd/cros_ec_dev.c b/drivers/mfd/cros_ec_dev.c
> index 39e611695053..c43026754718 100644
> --- a/drivers/mfd/cros_ec_dev.c
> +++ b/drivers/mfd/cros_ec_dev.c
> @@ -211,7 +211,7 @@ static int ec_device_probe(struct platform_device *pdev)
>          * explicitly added on platforms that don't have the PD notifier ACPI
>          * device entry defined.
>          */
> -       if (IS_ENABLED(CONFIG_OF)) {
> +       if (IS_ENABLED(CONFIG_OF) && &pdev->dev.of_node) {
I observe that when we have CONFIG_OF && !CONFIG_ACPI , the
cros_usbpd_notify_probe_plat() function doesn't get called. I think
adding "pdev->dev.of_node" causes the if clause to always evaluate to
false.
I think the check here would be :
            if (IS_ENABLED(CONFIG_OF) && ec->ec_dev->dev->of_node)
and then remove check for of_node from cros_usbpd_notify.c

Also, should this change be split into a separate patch (because it is
in the mfd driver)?

So, in summary, my proposed additions to the edits you suggested are:
- Remove IS_ENABLED(CONFIG_OF)... checks from
cros_usbpd_notify_probe_plat() and cros_usbpd_notify_remove_plat()
- Change check in cros_ec_dev to be:
              if (IS_ENABLED(CONFIG_OF) && ec->ec_dev->dev->of_node)

WDYT? Could you kindly try this on your kevin configuration? I've
tried it for the cases "CONFIG_OF && !CONFIG_ACPI" and "!CONFIG_OF &&
CONFIG_ACPI" but not the third one (CONFIG_OF && CONFIG_ACPI) since I
don't have an environment to test with (I can confirm it builds).

Thanks as always for helping iterate on this.


>                 if (cros_ec_check_features(ec, EC_FEATURE_USB_PD)) {
>                         retval = mfd_add_hotplug_devices(ec->dev,
>                                         cros_usbpd_notify_cells,
>
>
> > 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 */
> >
>
> Cheers,
>  Enric

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