Re: [char-misc-next v3 3/8] watchdog: mei_wdt: implement MEI iAMT watchdog driver

[Guenter Roeck <linux@roeck-us.net>]

On 12/21/2015 03:17 PM, Tomas Winkler wrote:
> Create a driver with the generic watchdog interface
> for the MEI iAMT watchdog device.
>
> Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
> Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
> ---
> V2: The watchdog device is no longer dynamically allocated in separate structure
> V3: Revert back to dynamically allocated watchdog device wrapper
>
>   Documentation/misc-devices/mei/mei.txt |  12 +-
>   MAINTAINERS                            |   1 +
>   drivers/watchdog/Kconfig               |  15 +
>   drivers/watchdog/Makefile              |   1 +
>   drivers/watchdog/mei_wdt.c             | 481 +++++++++++++++++++++++++++++++++
>   5 files changed, 504 insertions(+), 6 deletions(-)
>   create mode 100644 drivers/watchdog/mei_wdt.c
>
> diff --git a/Documentation/misc-devices/mei/mei.txt b/Documentation/misc-devices/mei/mei.txt
> index 91c1fa34f48b..2b80a0cd621f 100644
> --- a/Documentation/misc-devices/mei/mei.txt
> +++ b/Documentation/misc-devices/mei/mei.txt
> @@ -231,15 +231,15 @@ IT knows when a platform crashes even when there is a hard failure on the host.
>   The Intel AMT Watchdog is composed of two parts:
>   	1) Firmware feature - receives the heartbeats
>   	   and sends an event when the heartbeats stop.
> -	2) Intel MEI driver - connects to the watchdog feature, configures the
> -	   watchdog and sends the heartbeats.
> +	2) Intel MEI iAMT watchdog driver - connects to the watchdog feature,
> +	   configures the watchdog and sends the heartbeats.
>
> -The Intel MEI driver uses the kernel watchdog API to configure the Intel AMT
> -Watchdog and to send heartbeats to it. The default timeout of the
> +The Intel iAMT watchdog MEI driver uses the kernel watchdog API to configure
> +the Intel AMT Watchdog and to send heartbeats to it. The default timeout of the
>   watchdog is 120 seconds.
>
> -If the Intel AMT Watchdog feature does not exist (i.e. the connection failed),
> -the Intel MEI driver will disable the sending of heartbeats.
> +If the Intel AMT is not enabled in the firmware then the watchdog client won't enumerate
> +on the me client bus and watchdog devices won't be exposed.
>
>
>   Supported Chipsets
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9bff63cf326e..e655625c2c16 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -5666,6 +5666,7 @@ S:	Supported
>   F:	include/uapi/linux/mei.h
>   F:	include/linux/mei_cl_bus.h
>   F:	drivers/misc/mei/*
> +F:	drivers/watchdog/mei_wdt.c
>   F:	Documentation/misc-devices/mei/*
>
>   INTEL MIC DRIVERS (mic)
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 1c427beffadd..8ac51d69785c 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1154,6 +1154,21 @@ config SBC_EPX_C3_WATCHDOG
>   	  To compile this driver as a module, choose M here: the
>   	  module will be called sbc_epx_c3.
>
> +config INTEL_MEI_WDT
> +	tristate "Intel MEI iAMT Watchdog"
> +	depends on INTEL_MEI && X86
> +	select WATCHDOG_CORE
> +	---help---
> +	  A device driver for the Intel MEI iAMT watchdog.
> +
> +	  The Intel AMT Watchdog is an OS Health (Hang/Crash) watchdog.
> +	  Whenever the OS hangs or crashes, iAMT will send an event
> +	  to any subscriber to this event. The watchdog doesn't reset the
> +	  the platform.
> +
> +	  To compile this driver as a module, choose M here:
> +	  the module will be called mei_wdt.
> +
>   # M32R Architecture
>
>   # M68K Architecture
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 53d4827ddfe1..9069c9dd8aa8 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -123,6 +123,7 @@ obj-$(CONFIG_MACHZ_WDT) += machzwd.o
>   obj-$(CONFIG_SBC_EPX_C3_WATCHDOG) += sbc_epx_c3.o
>   obj-$(CONFIG_INTEL_SCU_WATCHDOG) += intel_scu_watchdog.o
>   obj-$(CONFIG_INTEL_MID_WATCHDOG) += intel-mid_wdt.o
> +obj-$(CONFIG_INTEL_MEI_WDT) += mei_wdt.o
>
>   # M32R Architecture
>
> diff --git a/drivers/watchdog/mei_wdt.c b/drivers/watchdog/mei_wdt.c
> new file mode 100644
> index 000000000000..5b28a1e95ac1
> --- /dev/null
> +++ b/drivers/watchdog/mei_wdt.c
> @@ -0,0 +1,481 @@
> +/*
> + * Intel Management Engine Interface (Intel MEI) Linux driver
> + * Copyright (c) 2015, Intel Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/interrupt.h>
> +#include <linux/watchdog.h>
> +
> +#include <linux/uuid.h>
> +#include <linux/mei_cl_bus.h>
> +
> +/*
> + * iAMT Watchdog Device
> + */
> +#define INTEL_AMT_WATCHDOG_ID "iamt_wdt"
> +
> +#define MEI_WDT_DEFAULT_TIMEOUT   120  /* seconds */
> +#define MEI_WDT_MIN_TIMEOUT       120  /* seconds */
> +#define MEI_WDT_MAX_TIMEOUT     65535  /* seconds */
> +
> +/* Commands */
> +#define MEI_MANAGEMENT_CONTROL 0x02
> +
> +/* MEI Management Control version number */
> +#define MEI_MC_VERSION_NUMBER  0x10
> +
> +/* Sub Commands */
> +#define MEI_MC_START_WD_TIMER_REQ  0x13
> +#define MEI_MC_STOP_WD_TIMER_REQ   0x14
> +
> +/**
> + * enum mei_wdt_state - internal watchdog state
> + *
> + * @MEI_WDT_IDLE: wd is idle and not opened
> + * @MEI_WDT_START: wd was opened, start was called
> + * @MEI_WDT_RUNNING: wd is expecting keep alive pings
> + * @MEI_WDT_STOPPING: wd is stopping and will move to IDLE
> + */
> +enum mei_wdt_state {
> +	MEI_WDT_IDLE,
> +	MEI_WDT_START,
> +	MEI_WDT_RUNNING,
> +	MEI_WDT_STOPPING,
> +};
> +
> +struct mei_wdt;
> +
> +/**
> + * struct mei_wdt_dev - watchdog device wrapper
> + *
> + * @wdd: watchdog device
> + * @wdt: back pointer to mei_wdt driver
> + * @refcnt: reference counter
> + */
> +struct mei_wdt_dev {
> +	struct watchdog_device wdd;
> +	struct mei_wdt *wdt;
> +	struct kref refcnt;
> +};
> +
> +/**
> + * struct mei_wdt - mei watchdog driver
> + * @mwd: watchdog device wrapper
> + *
> + * @cldev: mei watchdog client device
> + * @state: watchdog internal state
> + * @timeout: watchdog current timeout
> + */
> +struct mei_wdt {
> +	struct mei_wdt_dev *mwd;
> +
> +	struct mei_cl_device *cldev;
> +	enum mei_wdt_state state;
> +	u16 timeout;
> +};
> +
> +/*
> + * struct mei_mc_hdr - Management Control Command Header
> + *
> + * @command: Management Control (0x2)
> + * @bytecount: Number of bytes in the message beyond this byte
> + * @subcommand: Management Control Subcommand
> + * @versionnumber: Management Control Version (0x10)
> + */
> +struct mei_mc_hdr {
> +	u8 command;
> +	u8 bytecount;
> +	u8 subcommand;
> +	u8 versionnumber;
> +};
> +
> +/**
> + * struct mei_wdt_start_request watchdog start/ping
> + *
> + * @hdr: Management Control Command Header
> + * @timeout: timeout value
> + * @reserved: reserved (legacy)
> + */
> +struct mei_wdt_start_request {
> +	struct mei_mc_hdr hdr;
> +	u16 timeout;
> +	u8 reserved[17];
> +} __packed;
> +
> +/**
> + * struct mei_wdt_stop_request - watchdog stop
> + *
> + * @hdr: Management Control Command Header
> + */
> +struct mei_wdt_stop_request {
> +	struct mei_mc_hdr hdr;
> +} __packed;
> +
> +/**
> + * mei_wdt_ping - send wd start/ping command
> + *
> + * @wdt: mei watchdog device
> + *
> + * Return: 0 on success,
> + *         negative errno code on failure
> + */
> +static int mei_wdt_ping(struct mei_wdt *wdt)
> +{
> +	struct mei_wdt_start_request req;
> +	const size_t req_len = sizeof(req);
> +	int ret;
> +
> +	memset(&req, 0, req_len);
> +	req.hdr.command = MEI_MANAGEMENT_CONTROL;
> +	req.hdr.bytecount = req_len - offsetof(struct mei_mc_hdr, subcommand);
> +	req.hdr.subcommand = MEI_MC_START_WD_TIMER_REQ;
> +	req.hdr.versionnumber = MEI_MC_VERSION_NUMBER;
> +	req.timeout = wdt->timeout;
> +
> +	ret = mei_cldev_send(wdt->cldev, (u8 *)&req, req_len);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +/**
> + * mei_wdt_stop - send wd stop command
> + *
> + * @wdt: mei watchdog device
> + *
> + * Return: 0 on success,
> + *         negative errno code on failure
> + */
> +static int mei_wdt_stop(struct mei_wdt *wdt)
> +{
> +	struct mei_wdt_stop_request req;
> +	const size_t req_len = sizeof(req);
> +	int ret;
> +
> +	memset(&req, 0, req_len);
> +	req.hdr.command = MEI_MANAGEMENT_CONTROL;
> +	req.hdr.bytecount = req_len - offsetof(struct mei_mc_hdr, subcommand);
> +	req.hdr.subcommand = MEI_MC_STOP_WD_TIMER_REQ;
> +	req.hdr.versionnumber = MEI_MC_VERSION_NUMBER;
> +
> +	ret = mei_cldev_send(wdt->cldev, (u8 *)&req, req_len);
> +	if (ret < 0)
> +		return ret;
> +
> +	return 0;
> +}
> +
> +/**
> + * mei_wdt_ops_start - wd start command from the watchdog core.
> + *
> + * @wdd: watchdog device
> + *
> + * Return: 0 on success or -ENODEV;
> + */
> +static int mei_wdt_ops_start(struct watchdog_device *wdd)
> +{
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +	struct mei_wdt *wdt;
> +
> +	if (!mwd)
> +		return -ENODEV;
> +
I don't find a code path where this can be NULL. I also checked later patches,
but I just don't see it.

Can you clarify how this can happen ? If this is just for safety, it should go.
We would _want_ the driver to crash unless this is a valid condition.

Several other similar checks below.

> +	wdt = mwd->wdt;
> +
> +	wdt->state = MEI_WDT_START;
> +	wdd->timeout = wdt->timeout;
> +	return 0;
> +}
> +
> +/**
> + * mei_wdt_ops_stop - wd stop command from the watchdog core.
> + *
> + * @wdd: watchdog device
> + *
> + * Return: 0 if success, negative errno code for failure
> + */
> +static int mei_wdt_ops_stop(struct watchdog_device *wdd)
> +{
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +	struct mei_wdt *wdt;
> +	int ret;
> +
> +	if (!mwd)
> +		return -ENODEV;
> +
Same here.

> +	wdt = mwd->wdt;
> +
> +	if (wdt->state != MEI_WDT_RUNNING)
> +		return 0;
> +
> +	wdt->state = MEI_WDT_STOPPING;
> +
> +	ret = mei_wdt_stop(wdt);
> +	if (ret)
> +		return ret;
> +
> +	wdt->state = MEI_WDT_IDLE;
> +
Just wondering ... is MEI_WDT_STOPPING necessary ?
At least from an ops perspective, this function is atomic
(protected by a mutex in the watchdog core).

> +	return 0;
> +}
> +
> +/**
> + * mei_wdt_ops_ping - wd ping command from the watchdog core.
> + *
> + * @wdd: watchdog device
> + *
> + * Return: 0 if success, negative errno code on failure
> + */
> +static int mei_wdt_ops_ping(struct watchdog_device *wdd)
> +{
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +	struct mei_wdt *wdt;
> +	int ret;
> +
> +	if (!mwd)
> +		return -ENODEV;
> +
And here.

> +	wdt = mwd->wdt;
> +
> +	if (wdt->state != MEI_WDT_START && wdt->state != MEI_WDT_RUNNING)
> +		return 0;
> +
> +	ret = mei_wdt_ping(wdt);
> +	if (ret)
> +		return ret;
> +
> +	wdt->state = MEI_WDT_RUNNING;
> +
> +	return 0;
> +}
> +
> +/**
> + * mei_wdt_ops_set_timeout - wd set timeout command from the watchdog core.
> + *
> + * @wdd: watchdog device
> + * @timeout: timeout value to set
> + *
> + * Return: 0 if success, negative errno code for failure
> + */
> +static int mei_wdt_ops_set_timeout(struct watchdog_device *wdd,
> +				   unsigned int timeout)
> +{
> +
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +	struct mei_wdt *wdt;
> +
> +	if (!mwd)
> +		return -ENODEV;
> +

And here.

> +	wdt = mwd->wdt;
> +
> +	/* valid value is already checked by the caller */
> +	wdt->timeout = timeout;
> +	wdd->timeout = timeout;
> +
> +	return 0;
> +}
> +
> +static void mei_wdt_release(struct kref *ref)
> +{
> +	struct mei_wdt_dev *mwd = container_of(ref, struct mei_wdt_dev, refcnt);
> +
> +	kfree(mwd);
> +}
> +
> +static void mei_wdt_ops_ref(struct watchdog_device *wdd)
> +{
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +
> +	kref_get(&mwd->refcnt);
> +}
> +
> +static void mei_wdt_ops_unref(struct watchdog_device *wdd)
> +{
> +	struct mei_wdt_dev *mwd = watchdog_get_drvdata(wdd);
> +
> +	kref_put(&mwd->refcnt, mei_wdt_release);
> +}
> +
> +static const struct watchdog_ops wd_ops = {
> +	.owner       = THIS_MODULE,
> +	.start       = mei_wdt_ops_start,
> +	.stop        = mei_wdt_ops_stop,
> +	.ping        = mei_wdt_ops_ping,
> +	.set_timeout = mei_wdt_ops_set_timeout,
> +	.ref         = mei_wdt_ops_ref,
> +	.unref       = mei_wdt_ops_unref,
> +};
> +
> +static struct watchdog_info wd_info = {
> +	.identity = INTEL_AMT_WATCHDOG_ID,
> +	.options  = WDIOF_KEEPALIVEPING |
> +		    WDIOF_SETTIMEOUT |
> +		    WDIOF_ALARMONLY,
> +};
> +
> +/**
> + * mei_wdt_unregister - unregister from the watchdog subsystem
> + *
> + * @wdt: mei watchdog device
> + */
> +static void mei_wdt_unregister(struct mei_wdt *wdt)
> +{
> +	struct mei_wdt_dev *mwd = wdt->mwd;
> +
> +	if (!mwd)
> +		return;
> +
And here.

> +	watchdog_unregister_device(&mwd->wdd);
> +	wdt->mwd = NULL;
> +	wdt->state = MEI_WDT_IDLE;
> +	kref_put(&mwd->refcnt, mei_wdt_release);
> +}
> +
> +/**
> + * mei_wdt_register - register with the watchdog subsystem
> + *
> + * @wdt: mei watchdog device
> + *
> + * Return: 0 if success, negative errno code for failure
> + */
> +static int mei_wdt_register(struct mei_wdt *wdt)
> +{
> +	struct mei_wdt_dev *mwd;
> +	struct device *dev;
> +	int ret;
> +
> +	if (!wdt || !wdt->cldev)
> +		return -EINVAL;
> +
And here.

> +	dev = &wdt->cldev->dev;
> +
> +	mwd = kzalloc(sizeof(struct mei_wdt_dev), GFP_KERNEL);
> +	if (!mwd)
> +		return -ENOMEM;
> +
> +	mwd->wdt = wdt;
> +	mwd->wdd.info = &wd_info;
> +	mwd->wdd.ops = &wd_ops;
> +	mwd->wdd.parent = dev;
> +	mwd->wdd.timeout = MEI_WDT_DEFAULT_TIMEOUT;
> +	mwd->wdd.min_timeout = MEI_WDT_MIN_TIMEOUT;
> +	mwd->wdd.max_timeout = MEI_WDT_MAX_TIMEOUT;
> +	kref_init(&mwd->refcnt);
> +
> +	watchdog_set_drvdata(&mwd->wdd, mwd);
> +	ret = watchdog_register_device(&mwd->wdd);
> +	if (ret) {
> +		dev_err(dev, "unable to register watchdog device = %d.\n", ret);
> +		kref_put(&mwd->refcnt, mei_wdt_release);
> +		return ret;
> +	}
> +
> +	wdt->mwd = mwd;
> +	return 0;
> +}
> +
> +static int mei_wdt_probe(struct mei_cl_device *cldev,
> +			 const struct mei_cl_device_id *id)
> +{
> +	struct mei_wdt *wdt;
> +	int ret;
> +
> +	wdt = kzalloc(sizeof(struct mei_wdt), GFP_KERNEL);
> +	if (!wdt)
> +		return -ENOMEM;
> +
> +	wdt->timeout = MEI_WDT_DEFAULT_TIMEOUT;
> +	wdt->state = MEI_WDT_IDLE;
> +	wdt->cldev = cldev;
> +	mei_cldev_set_drvdata(cldev, wdt);
> +
> +	ret = mei_cldev_enable(cldev);
> +	if (ret < 0) {
> +		dev_err(&cldev->dev, "Could not enable cl device\n");
> +		goto err_out;
> +	}
> +
> +	wd_info.firmware_version = mei_cldev_ver(cldev);
> +
> +	ret = mei_wdt_register(wdt);
> +	if (ret)
> +		goto err_disable;
> +
> +	return 0;
> +
> +err_disable:
> +	mei_cldev_disable(cldev);
> +
> +err_out:
> +	kfree(wdt);
> +
> +	return ret;
> +}
> +
> +static int mei_wdt_remove(struct mei_cl_device *cldev)
> +{
> +	struct mei_wdt *wdt = mei_cldev_get_drvdata(cldev);
> +
> +	mei_wdt_unregister(wdt);
> +
> +	mei_cldev_disable(cldev);
> +
> +	kfree(wdt);
> +
> +	return 0;
> +}
> +
> +#define MEI_UUID_WD UUID_LE(0x05B79A6F, 0x4628, 0x4D7F, \
> +			    0x89, 0x9D, 0xA9, 0x15, 0x14, 0xCB, 0x32, 0xAB)
> +
> +static struct mei_cl_device_id mei_wdt_tbl[] = {
> +	{ .uuid = MEI_UUID_WD, .version = 0x1},
> +	/* required last entry */
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(mei, mei_wdt_tbl);
> +
> +static struct mei_cl_driver mei_wdt_driver = {
> +	.id_table = mei_wdt_tbl,
> +	.name = KBUILD_MODNAME,
> +
> +	.probe = mei_wdt_probe,
> +	.remove = mei_wdt_remove,
> +};
> +
> +static int __init mei_wdt_init(void)
> +{
> +	int ret;
> +
> +	ret = mei_cldev_driver_register(&mei_wdt_driver);
> +	if (ret) {
> +		pr_err(KBUILD_MODNAME ": module registration failed\n");
> +		return ret;
> +	}
> +	return 0;
> +}
> +
> +static void __exit mei_wdt_exit(void)
> +{
> +	mei_cldev_driver_unregister(&mei_wdt_driver);
> +}
> +
> +module_init(mei_wdt_init);
> +module_exit(mei_wdt_exit);
> +
> +MODULE_AUTHOR("Intel Corporation");
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Device driver for Intel MEI iAMT watchdog");
>