Re: [PATCH v3 11/12] misc: throttler: Add Chrome OS EC throttler

[Brian Norris]

Hi,

On Thu, Jun 14, 2018 at 12:47:11PM -0700, Matthias Kaehlcke wrote:
> The driver subscribes to throttling events from the Chrome OS
> embedded controller and enables/disables system throttling based
> on these events.
> 
> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> Reviewed-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx>

One suggestion, and otherwise:

Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx>

> ---
> Changes in v3:
> - change module license to GPL v2 as in the SPDX identifier
> - don't instantiate the throttler through the DT (instantiation
>   by CrOS EC MFD in a separate patch)
> 
> Changes in v2:
> - added SPDX line instead of license boiler-plate
> - use macro to avoid splitting line
> - changed variable name for throttler from 'cte' to 'ce_thr'
> - formatting fixes
> - Kconfig: removed odd dashes around 'help'
> - added 'Reviewed-by' tag
> 
>  drivers/misc/throttler/Kconfig             |  10 ++
>  drivers/misc/throttler/Makefile            |   1 +
>  drivers/misc/throttler/cros_ec_throttler.c | 109 +++++++++++++++++++++
>  3 files changed, 120 insertions(+)
>  create mode 100644 drivers/misc/throttler/cros_ec_throttler.c
> 
> diff --git a/drivers/misc/throttler/Kconfig b/drivers/misc/throttler/Kconfig
> index 8b2e63b2ef48..ef984c96f67b 100644
> --- a/drivers/misc/throttler/Kconfig
> +++ b/drivers/misc/throttler/Kconfig
> @@ -20,4 +20,14 @@ menuconfig THROTTLER_DEBUG
>  
>  	  Choose N unless you want to debug throttler drivers.
>  
> +config CROS_EC_THROTTLER
> +	tristate "Throttler event monitor for the Chrome OS Embedded Controller"
> +	depends on MFD_CROS_EC
> +	help
> +	  This driver adds support to throttle the system in reaction to
> +	  Chrome OS EC events.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called cros_ec_throttler.
> +
>  endif # THROTTLER
> diff --git a/drivers/misc/throttler/Makefile b/drivers/misc/throttler/Makefile
> index c8d920cee315..d9b2a77dabc9 100644
> --- a/drivers/misc/throttler/Makefile
> +++ b/drivers/misc/throttler/Makefile
> @@ -1 +1,2 @@
>  obj-$(CONFIG_THROTTLER)		+= core.o
> +obj-$(CONFIG_CROS_EC_THROTTLER)	+= cros_ec_throttler.o
> diff --git a/drivers/misc/throttler/cros_ec_throttler.c b/drivers/misc/throttler/cros_ec_throttler.c
> new file mode 100644
> index 000000000000..f1e9fc0a6284
> --- /dev/null
> +++ b/drivers/misc/throttler/cros_ec_throttler.c
> @@ -0,0 +1,109 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for throttling triggered by events from the Chrome OS Embedded
> + * Controller.
> + *
> + * Copyright (C) 2018 Google, Inc.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/mfd/cros_ec.h>
> +#include <linux/module.h>
> +#include <linux/notifier.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/throttler.h>
> +
> +#define nb_to_ce_thr(nb) container_of(nb, struct cros_ec_throttler, nb)
> +
> +struct cros_ec_throttler {
> +	struct cros_ec_device *ec;
> +	struct throttler *throttler;
> +	struct notifier_block nb;
> +};
> +
> +static int cros_ec_throttler_event(struct notifier_block *nb,
> +	unsigned long queued_during_suspend, void *_notify)
> +{
> +	struct cros_ec_throttler *ce_thr = nb_to_ce_thr(nb);
> +	u32 host_event;
> +
> +	host_event = cros_ec_get_host_event(ce_thr->ec);
> +	if (host_event & EC_HOST_EVENT_MASK(EC_HOST_EVENT_THROTTLE_START)) {
> +		throttler_set_level(ce_thr->throttler, 1);
> +
> +		return NOTIFY_OK;
> +	} else if (host_event &
> +		   EC_HOST_EVENT_MASK(EC_HOST_EVENT_THROTTLE_STOP)) {
> +		throttler_set_level(ce_thr->throttler, 0);
> +
> +		return NOTIFY_OK;
> +	}
> +
> +	return NOTIFY_DONE;
> +}
> +
> +static int cros_ec_throttler_probe(struct platform_device *pdev)
> +{
> +	struct cros_ec_throttler *ce_thr;
> +	struct device *dev = &pdev->dev;
> +	int ret;
> +
> +	ce_thr = devm_kzalloc(dev, sizeof(*ce_thr), GFP_KERNEL);
> +	if (!ce_thr)
> +		return -ENOMEM;
> +
> +	ce_thr->ec = dev_get_drvdata(pdev->dev.parent);
> +
> +	/*
> +	 * The core code uses the DT node of the throttler to identify its
> +	 * throttling devices and rates. The CrOS EC throttler is a sub-device
> +	 * of the CrOS EC MFD device and doesn't have its own device node. Use
> +	 * the node of the MFD device instead.
> +	 */
> +	dev->of_node = dev->parent->of_node;

It might be better to get the appropriate 'parent' (and of_node) pointer
via the 'cros_ec_device' you retrieve above, since the parent might be
different depending on my suggestions in patch 12...I think.

Brian

> +
> +	ce_thr->throttler = throttler_setup(dev);
> +	if (IS_ERR(ce_thr->throttler))
> +		return PTR_ERR(ce_thr->throttler);
> +
> +	dev_set_drvdata(dev, ce_thr);
> +
> +	ce_thr->nb.notifier_call = cros_ec_throttler_event;
> +	ret = blocking_notifier_chain_register(&ce_thr->ec->event_notifier,
> +					       &ce_thr->nb);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to register notifier\n");
> +		throttler_teardown(ce_thr->throttler);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int cros_ec_throttler_remove(struct platform_device *pdev)
> +{
> +	struct cros_ec_throttler *ce_thr = platform_get_drvdata(pdev);
> +
> +	blocking_notifier_chain_unregister(&ce_thr->ec->event_notifier,
> +					   &ce_thr->nb);
> +
> +	throttler_teardown(ce_thr->throttler);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver cros_ec_throttler_driver = {
> +	.driver = {
> +		.name = "cros-ec-throttler",
> +	},
> +	.probe		= cros_ec_throttler_probe,
> +	.remove		= cros_ec_throttler_remove,
> +};
> +
> +module_platform_driver(cros_ec_throttler_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Matthias Kaehlcke <mka@xxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("Chrome OS EC Throttler");
> -- 
> 2.18.0.rc1.242.g61856ae69a-goog
>