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Subject: Re: [PATCH 03/11] firmware: arm_scmi: introduce common protocol
 interface
To:     Cristian Marussi <cristian.marussi@arm.com>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        sudeep.holla@arm.com, lukasz.luba@arm.com,
        james.quinlan@broadcom.com, Jonathan.Cameron@Huawei.com,
        f.fainelli@gmail.com, etienne.carriere@linaro.org,
        vincent.guittot@linaro.org, souvik.chakravarty@arm.com
References: <20201014150545.44807-1-cristian.marussi@arm.com>
 <20201014150545.44807-4-cristian.marussi@arm.com>
 <64254fdf-dcb3-b27f-9624-de2abacf55d2@linaro.org>
 <20201021102741.GB20482@e120937-lin>
From:   Thara Gopinath <thara.gopinath@linaro.org>
Message-ID: <0f931edf-4cae-d393-f59d-1609c03ab9e7@linaro.org>
Date:   Mon, 26 Oct 2020 09:07:12 -0400
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On 10/21/20 6:27 AM, Cristian Marussi wrote:
> On Tue, Oct 20, 2020 at 10:47:10PM -0400, Thara Gopinath wrote:
>>
>>
>> On 10/14/20 11:05 AM, Cristian Marussi wrote:
>>> Introduce generic get_ops/put_ops handle operations: any protocol, both
>>> standard or custom, now exposes its operations through this common
>>> interface which internally takes care to account for protocols' usage:
>>> protocols' initialization is now performed on demand as soon as the first
>>> user shows up while deinitialization (if any) is performed once
>>> the last user of a protocol has gone.
>>> Registered events' notifier are tracked too against the related protocol.
>>> Convert all SCMI drivers to the new interface too.
>>>
>>> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
>>> ---
>>
>> [...]
>>
>>
>>> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
>>> index bad1d0130e96..049220efd227 100644
>>> --- a/drivers/firmware/arm_scmi/driver.c
>>> +++ b/drivers/firmware/arm_scmi/driver.c
>>> @@ -585,7 +585,7 @@ void *scmi_get_proto_priv(const struct scmi_handle *handle, u8 protocol_id)
>>>     * Return: A reference to an initialized protocol instance or error on failure.
>>>     */
>>>    static struct scmi_protocol_instance * __must_check
>>> -scmi_get_protocol_instance(struct scmi_handle *handle, u8 protocol_id)
>>> +scmi_get_protocol_instance(const struct scmi_handle *handle, u8 protocol_id)
>>>    {
>>>    	int ret = -ENOMEM;
>>>    	void *gid;
>>> @@ -655,7 +655,7 @@ scmi_get_protocol_instance(struct scmi_handle *handle, u8 protocol_id)
>>>     *
>>>     * Return: 0 if protocol was acquired successfully.
>>>     */
>>> -int scmi_acquire_protocol(struct scmi_handle *handle, u8 protocol_id)
>>> +int scmi_acquire_protocol(const struct scmi_handle *handle, u8 protocol_id)
>>>    {
>>>    	return IS_ERR(scmi_get_protocol_instance(handle, protocol_id));
>>>    }
>>> @@ -668,7 +668,7 @@ int scmi_acquire_protocol(struct scmi_handle *handle, u8 protocol_id)
>>>     * Remove one user for the specified protocol and triggers de-initialization
>>>     * and resources de-allocation once the last user has gone.
>>>     */
>>> -void scmi_release_protocol(struct scmi_handle *handle, u8 protocol_id)
>>> +void scmi_release_protocol(const struct scmi_handle *handle, u8 protocol_id)
>>>    {
>>>    	struct scmi_info *info = handle_to_scmi_info(handle);
>>>    	struct scmi_protocol_instance *pi;
>>> @@ -700,6 +700,29 @@ void scmi_release_protocol(struct scmi_handle *handle, u8 protocol_id)
>>>    	mutex_unlock(&info->protocols_mtx);
>>>    }
>>> +/**
>>> + * scmi_get_protocol_operations  - Get protocol operations
>>> + * @handle: A reference to the SCMI platform instance.
>>> + * @protocol_id: The protocol being requested.
>>> + *
>>> + * Get hold of a protocol accounting for its usage, eventually triggering its
>>> + * initialization, and returning the protocol specific operations.
>>> + *
>>> + * Return: A reference to the requested protocol operations or error.
>>> + *	   Must be checked for errors by caller.
>>> + */
>>> +static const void __must_check
>>> +*scmi_get_protocol_operations(const struct scmi_handle *handle, u8 protocol_id)
>>> +{
>>> +	struct scmi_protocol_instance *pi;
>>> +
>>> +	pi = scmi_get_protocol_instance(handle, protocol_id);
>>> +	if (IS_ERR(pi))
>>> +		return pi;
>>> +
>>> +	return pi->proto->ops;
>>> +} > +
>>>    void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
>>>    				     u8 *prot_imp)
>>>    {
>>> @@ -975,6 +998,8 @@ static int scmi_probe(struct platform_device *pdev)
>>>    	handle = &info->handle;
>>>    	handle->dev = info->dev;
>>>    	handle->version = &info->version;
>>> +	handle->get_ops = scmi_get_protocol_operations;
>>> +	handle->put_ops = scmi_release_protocol;
>>
>>
>> Why do you need get_ops and put_ops? Why not have the drivers call
>> scmi_acquire_protocol and scmi_release_protocol directly and get the ops
>> from retrieved scmi_get_protocol_instance ? IMHO, this makes it more
>> readable. Also, this will make the usage of scmi_acquire_protocol and
>> scmi_release_protocol more consistent. Right now, notify.c uses
>> scmi_acquire_protocol to acquire protocol because there is no need for ops
>> and other drivers use get_ops to acquire protocol. Kind of confusing..
>>
> 
> Trying to avoid exporting new synbols if not strictly needed, I exposed
> get_ops()/put_ops() via handle for the usage of the SCMI drivers users,
> while keeping scmi_acquire/release as internal non-exported wrappers used
> only by the SCMI core itself like notifications.
> You cannot call acquire/release from a loadable module as of now.
> 
> Additionally I thougt to add these wrappers for cases in which like
> notifications you don't need the ops really (like notif or base) nor
> the related forced __must_check(like notif), but just to get hold of
> the protocol to avoid it being possibly unloaded.
> 
> I would antyway keep the get_ops/put_ops and I could just drop
> acquire/release if confusing and use the raw ops methods also internally,
> properly checking for the result everytime: currently notifications core
> takes care to acquire a protocol only once the requested event has been
> registered by some protocol (i.e. event handler is NOT pending) so that
> I do not trigger a protocol initialization when registering a notifier
> against a still unknown event: as a consequence acquire/release when
> called in the notif context cannot fail, so I don;t check.
> 
> I'll try to simplify this though.

I think a standard interface is better. So either a get_ops/put_ops or 
acquire_release that can be called by all users/drivers of a protocol 
will standardize it. I will wait for your next version.
> 
> Regards
> 
> Cristian
> 
>> -- 
>> Warm Regards
>> Thara
>>
>>>    	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
>>>    	if (ret)
>>> diff --git a/drivers/firmware/arm_scmi/notify.c b/drivers/firmware/arm_scmi/notify.c
>>> index eae58b2a92cc..02b00af9b08f 100644
>>> --- a/drivers/firmware/arm_scmi/notify.c
>>> +++ b/drivers/firmware/arm_scmi/notify.c
>>> @@ -367,7 +367,7 @@ static struct scmi_event_handler *
>>>    scmi_get_active_handler(struct scmi_notify_instance *ni, u32 evt_key);
>>>    static void scmi_put_active_handler(struct scmi_notify_instance *ni,
>>>    				    struct scmi_event_handler *hndl);
>>> -static void scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
>>> +static bool scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
>>>    				      struct scmi_event_handler *hndl);
>>>    /**
>>> @@ -899,9 +899,21 @@ static inline int scmi_bind_event_handler(struct scmi_notify_instance *ni,
>>>    	if (!r_evt)
>>>    		return -EINVAL;
>>> -	/* Remove from pending and insert into registered */
>>> +	/*
>>> +	 * Remove from pending and insert into registered while getting hold
>>> +	 * of protocol instance.
>>> +	 */
>>>    	hash_del(&hndl->hash);
>>> +	/*
>>> +	 * Acquire protocols only for NON pending handlers, so as NOT to trigger
>>> +	 * protocol initialization when a notifier is registered against a still
>>> +	 * not registered protocol, since it would make little sense to force init
>>> +	 * protocols for which still no SCMI driver user exists: they wouldn't
>>> +	 * emit any event anyway till some SCMI driver starts using it.
>>> +	 */
>>> +	scmi_acquire_protocol(ni->handle, KEY_XTRACT_PROTO_ID(hndl->key));
>>>    	hndl->r_evt = r_evt;
>>> +
>>>    	mutex_lock(&r_evt->proto->registered_mtx);
>>>    	hash_add(r_evt->proto->registered_events_handlers,
>>>    		 &hndl->hash, hndl->key);
>>> @@ -1192,41 +1204,65 @@ static int scmi_disable_events(struct scmi_event_handler *hndl)
>>>     * * unregister and free the handler itself
>>>     *
>>>     * Context: Assumes all the proper locking has been managed by the caller.
>>> + *
>>> + * Return: True if handler was freed (users dropped to zero)
>>>     */
>>> -static void scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
>>> +static bool scmi_put_handler_unlocked(struct scmi_notify_instance *ni,
>>>    				      struct scmi_event_handler *hndl)
>>>    {
>>> +	bool freed = false;
>>> +
>>>    	if (refcount_dec_and_test(&hndl->users)) {
>>>    		if (!IS_HNDL_PENDING(hndl))
>>>    			scmi_disable_events(hndl);
>>>    		scmi_free_event_handler(hndl);
>>> +		freed = true;
>>>    	}
>>> +
>>> +	return freed;
>>>    }
>>>    static void scmi_put_handler(struct scmi_notify_instance *ni,
>>>    			     struct scmi_event_handler *hndl)
>>>    {
>>> +	bool freed;
>>> +	u8 protocol_id;
>>>    	struct scmi_registered_event *r_evt = hndl->r_evt;
>>>    	mutex_lock(&ni->pending_mtx);
>>> -	if (r_evt)
>>> +	if (r_evt) {
>>> +		protocol_id = r_evt->proto->id;
>>>    		mutex_lock(&r_evt->proto->registered_mtx);
>>> +	}
>>> -	scmi_put_handler_unlocked(ni, hndl);
>>> +	freed = scmi_put_handler_unlocked(ni, hndl);
>>> -	if (r_evt)
>>> +	if (r_evt) {
>>>    		mutex_unlock(&r_evt->proto->registered_mtx);
>>> +		/*
>>> +		 * Only registered handler acquired protocol; must be here
>>> +		 * released only AFTER unlocking registered_mtx, since
>>> +		 * releasing a protocol can trigger its de-initialization
>>> +		 * (ie. including r_evt and registered_mtx)
>>> +		 */
>>> +		if (freed)
>>> +			scmi_release_protocol(ni->handle, protocol_id);
>>> +	}
>>>    	mutex_unlock(&ni->pending_mtx);
>>>    }
>>>    static void scmi_put_active_handler(struct scmi_notify_instance *ni,
>>>    				    struct scmi_event_handler *hndl)
>>>    {
>>> +	bool freed;
>>>    	struct scmi_registered_event *r_evt = hndl->r_evt;
>>> +	u8 protocol_id = r_evt->proto->id;
>>>    	mutex_lock(&r_evt->proto->registered_mtx);
>>> -	scmi_put_handler_unlocked(ni, hndl);
>>> +	freed = scmi_put_handler_unlocked(ni, hndl);
>>>    	mutex_unlock(&r_evt->proto->registered_mtx);
>>> +	if (freed)
>>> +		scmi_release_protocol(ni->handle, protocol_id);
>>>    }
>>>    /**
>>> diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
>>> index 13e215f359fb..bd9cb2583557 100644
>>> --- a/drivers/firmware/arm_scmi/perf.c
>>> +++ b/drivers/firmware/arm_scmi/perf.c
>>> @@ -857,7 +857,7 @@ static const struct scmi_event_ops perf_event_ops = {
>>>    	.fill_custom_report = scmi_perf_fill_custom_report,
>>>    };
>>> -static int scmi_perf_protocol_init(struct scmi_handle *handle)
>>> +static int scmi_perf_protocol_init(const struct scmi_handle *handle)
>>>    {
>>>    	int domain;
>>>    	u32 version;
>>> @@ -896,7 +896,6 @@ static int scmi_perf_protocol_init(struct scmi_handle *handle)
>>>    				      pinfo->num_domains);
>>>    	pinfo->version = version;
>>> -	handle->perf_ops = &perf_ops;
>>>    	return scmi_set_proto_priv(handle, SCMI_PROTOCOL_PERF, pinfo);
>>>    }
>>> diff --git a/drivers/firmware/arm_scmi/power.c b/drivers/firmware/arm_scmi/power.c
>>> index e0b29ed4e09a..1e026b5530a7 100644
>>> --- a/drivers/firmware/arm_scmi/power.c
>>> +++ b/drivers/firmware/arm_scmi/power.c
>>> @@ -262,7 +262,7 @@ static const struct scmi_event_ops power_event_ops = {
>>>    	.fill_custom_report = scmi_power_fill_custom_report,
>>>    };
>>> -static int scmi_power_protocol_init(struct scmi_handle *handle)
>>> +static int scmi_power_protocol_init(const struct scmi_handle *handle)
>>>    {
>>>    	int domain;
>>>    	u32 version;
>>> @@ -297,7 +297,6 @@ static int scmi_power_protocol_init(struct scmi_handle *handle)
>>>    				      pinfo->num_domains);
>>>    	pinfo->version = version;
>>> -	handle->power_ops = &power_ops;
>>>    	return scmi_set_proto_priv(handle, SCMI_PROTOCOL_POWER, pinfo);
>>>    }
>>> diff --git a/drivers/firmware/arm_scmi/reset.c b/drivers/firmware/arm_scmi/reset.c
>>> index f70e9b5108d5..b7da4de0e56e 100644
>>> --- a/drivers/firmware/arm_scmi/reset.c
>>> +++ b/drivers/firmware/arm_scmi/reset.c
>>> @@ -274,7 +274,7 @@ static const struct scmi_event_ops reset_event_ops = {
>>>    	.fill_custom_report = scmi_reset_fill_custom_report,
>>>    };
>>> -static int scmi_reset_protocol_init(struct scmi_handle *handle)
>>> +static int scmi_reset_protocol_init(const struct scmi_handle *handle)
>>>    {
>>>    	int domain;
>>>    	u32 version;
>>> @@ -309,7 +309,6 @@ static int scmi_reset_protocol_init(struct scmi_handle *handle)
>>>    				      pinfo->num_domains);
>>>    	pinfo->version = version;
>>> -	handle->reset_ops = &reset_ops;
>>>    	return scmi_set_proto_priv(handle, SCMI_PROTOCOL_RESET, pinfo);
>>>    }
>>> diff --git a/drivers/firmware/arm_scmi/scmi_pm_domain.c b/drivers/firmware/arm_scmi/scmi_pm_domain.c
>>> index 9e44479f0284..bfea56f77890 100644
>>> --- a/drivers/firmware/arm_scmi/scmi_pm_domain.c
>>> +++ b/drivers/firmware/arm_scmi/scmi_pm_domain.c
>>> @@ -2,7 +2,7 @@
>>>    /*
>>>     * SCMI Generic power domain support.
>>>     *
>>> - * Copyright (C) 2018 ARM Ltd.
>>> + * Copyright (C) 2018-2020 ARM Ltd.
>>>     */
>>>    #include <linux/err.h>
>>> @@ -11,6 +11,8 @@
>>>    #include <linux/pm_domain.h>
>>>    #include <linux/scmi_protocol.h>
>>> +static const struct scmi_power_ops *power_ops;
>>> +
>>>    struct scmi_pm_domain {
>>>    	struct generic_pm_domain genpd;
>>>    	const struct scmi_handle *handle;
>>> @@ -25,16 +27,15 @@ static int scmi_pd_power(struct generic_pm_domain *domain, bool power_on)
>>>    	int ret;
>>>    	u32 state, ret_state;
>>>    	struct scmi_pm_domain *pd = to_scmi_pd(domain);
>>> -	const struct scmi_power_ops *ops = pd->handle->power_ops;
>>>    	if (power_on)
>>>    		state = SCMI_POWER_STATE_GENERIC_ON;
>>>    	else
>>>    		state = SCMI_POWER_STATE_GENERIC_OFF;
>>> -	ret = ops->state_set(pd->handle, pd->domain, state);
>>> +	ret = power_ops->state_set(pd->handle, pd->domain, state);
>>>    	if (!ret)
>>> -		ret = ops->state_get(pd->handle, pd->domain, &ret_state);
>>> +		ret = power_ops->state_get(pd->handle, pd->domain, &ret_state);
>>>    	if (!ret && state != ret_state)
>>>    		return -EIO;
>>> @@ -61,10 +62,14 @@ static int scmi_pm_domain_probe(struct scmi_device *sdev)
>>>    	struct generic_pm_domain **domains;
>>>    	const struct scmi_handle *handle = sdev->handle;
>>> -	if (!handle || !handle->power_ops)
>>> +	if (!handle)
>>>    		return -ENODEV;
>>> -	num_domains = handle->power_ops->num_domains_get(handle);
>>> +	power_ops = handle->get_ops(handle, SCMI_PROTOCOL_POWER);
>>> +	if (IS_ERR(power_ops))
>>> +		return PTR_ERR(power_ops);
>>> +
>>> +	num_domains = power_ops->num_domains_get(handle);
>>>    	if (num_domains < 0) {
>>>    		dev_err(dev, "number of domains not found\n");
>>>    		return num_domains;
>>> @@ -85,14 +90,14 @@ static int scmi_pm_domain_probe(struct scmi_device *sdev)
>>>    	for (i = 0; i < num_domains; i++, scmi_pd++) {
>>>    		u32 state;
>>> -		if (handle->power_ops->state_get(handle, i, &state)) {
>>> +		if (power_ops->state_get(handle, i, &state)) {
>>>    			dev_warn(dev, "failed to get state for domain %d\n", i);
>>>    			continue;
>>>    		}
>>>    		scmi_pd->domain = i;
>>>    		scmi_pd->handle = handle;
>>> -		scmi_pd->name = handle->power_ops->name_get(handle, i);
>>> +		scmi_pd->name = power_ops->name_get(handle, i);
>>>    		scmi_pd->genpd.name = scmi_pd->name;
>>>    		scmi_pd->genpd.power_off = scmi_pd_power_off;
>>>    		scmi_pd->genpd.power_on = scmi_pd_power_on;
>>> @@ -111,6 +116,13 @@ static int scmi_pm_domain_probe(struct scmi_device *sdev)
>>>    	return 0;
>>>    }
>>> +static void scmi_pm_domain_remove(struct scmi_device *sdev)
>>> +{
>>> +	const struct scmi_handle *handle = sdev->handle;
>>> +
>>> +	handle->put_ops(handle, SCMI_PROTOCOL_POWER);
>>> +}
>>> +
>>>    static const struct scmi_device_id scmi_id_table[] = {
>>>    	{ SCMI_PROTOCOL_POWER, "genpd" },
>>>    	{ },
>>> @@ -120,6 +132,7 @@ MODULE_DEVICE_TABLE(scmi, scmi_id_table);
>>>    static struct scmi_driver scmi_power_domain_driver = {
>>>    	.name = "scmi-power-domain",
>>>    	.probe = scmi_pm_domain_probe,
>>> +	.remove = scmi_pm_domain_remove,
>>>    	.id_table = scmi_id_table,
>>>    };
>>>    module_scmi_driver(scmi_power_domain_driver);
>>> diff --git a/drivers/firmware/arm_scmi/sensors.c b/drivers/firmware/arm_scmi/sensors.c
>>> index 8a0a599558ba..e0129dcd322f 100644
>>> --- a/drivers/firmware/arm_scmi/sensors.c
>>> +++ b/drivers/firmware/arm_scmi/sensors.c
>>> @@ -334,7 +334,7 @@ static const struct scmi_event_ops sensor_event_ops = {
>>>    	.fill_custom_report = scmi_sensor_fill_custom_report,
>>>    };
>>> -static int scmi_sensors_protocol_init(struct scmi_handle *handle)
>>> +static int scmi_sensors_protocol_init(const struct scmi_handle *handle)
>>>    {
>>>    	u32 version;
>>>    	struct sensors_info *sinfo;
>>> @@ -364,7 +364,6 @@ static int scmi_sensors_protocol_init(struct scmi_handle *handle)
>>>    				      sinfo->num_sensors);
>>>    	sinfo->version = version;
>>> -	handle->sensor_ops = &sensor_ops;
>>>    	return scmi_set_proto_priv(handle, SCMI_PROTOCOL_SENSOR, sinfo);
>>>    }
>>> diff --git a/drivers/firmware/arm_scmi/system.c b/drivers/firmware/arm_scmi/system.c
>>> index 8f53f93c63ca..30e3510c1f07 100644
>>> --- a/drivers/firmware/arm_scmi/system.c
>>> +++ b/drivers/firmware/arm_scmi/system.c
>>> @@ -101,7 +101,7 @@ static const struct scmi_event_ops system_event_ops = {
>>>    	.fill_custom_report = scmi_system_fill_custom_report,
>>>    };
>>> -static int scmi_system_protocol_init(struct scmi_handle *handle)
>>> +static int scmi_system_protocol_init(const struct scmi_handle *handle)
>>>    {
>>>    	u32 version;
>>>    	struct scmi_system_info *pinfo;
>>> diff --git a/drivers/hwmon/scmi-hwmon.c b/drivers/hwmon/scmi-hwmon.c
>>> index d421e691318b..27ef71996a15 100644
>>> --- a/drivers/hwmon/scmi-hwmon.c
>>> +++ b/drivers/hwmon/scmi-hwmon.c
>>> @@ -2,7 +2,7 @@
>>>    /*
>>>     * System Control and Management Interface(SCMI) based hwmon sensor driver
>>>     *
>>> - * Copyright (C) 2018 ARM Ltd.
>>> + * Copyright (C) 2018-2020 ARM Ltd.
>>>     * Sudeep Holla <sudeep.holla@arm.com>
>>>     */
>>> @@ -13,6 +13,8 @@
>>>    #include <linux/sysfs.h>
>>>    #include <linux/thermal.h>
>>> +static const struct scmi_sensor_ops *sensor_ops;
>>> +
>>>    struct scmi_sensors {
>>>    	const struct scmi_handle *handle;
>>>    	const struct scmi_sensor_info **info[hwmon_max];
>>> @@ -72,7 +74,7 @@ static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
>>>    	const struct scmi_handle *h = scmi_sensors->handle;
>>>    	sensor = *(scmi_sensors->info[type] + channel);
>>> -	ret = h->sensor_ops->reading_get(h, sensor->id, &value);
>>> +	ret = sensor_ops->reading_get(h, sensor->id, &value);
>>>    	if (ret)
>>>    		return ret;
>>> @@ -170,10 +172,14 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
>>>    	const struct hwmon_channel_info **ptr_scmi_ci;
>>>    	const struct scmi_handle *handle = sdev->handle;
>>> -	if (!handle || !handle->sensor_ops)
>>> +	if (!handle)
>>>    		return -ENODEV;
>>> -	nr_sensors = handle->sensor_ops->count_get(handle);
>>> +	sensor_ops = handle->get_ops(handle, SCMI_PROTOCOL_SENSOR);
>>> +	if (IS_ERR(sensor_ops))
>>> +		return PTR_ERR(sensor_ops);
>>> +
>>> +	nr_sensors = sensor_ops->count_get(handle);
>>>    	if (!nr_sensors)
>>>    		return -EIO;
>>> @@ -184,7 +190,7 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
>>>    	scmi_sensors->handle = handle;
>>>    	for (i = 0; i < nr_sensors; i++) {
>>> -		sensor = handle->sensor_ops->info_get(handle, i);
>>> +		sensor = sensor_ops->info_get(handle, i);
>>>    		if (!sensor)
>>>    			return -EINVAL;
>>> @@ -234,7 +240,7 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
>>>    	}
>>>    	for (i = nr_sensors - 1; i >= 0 ; i--) {
>>> -		sensor = handle->sensor_ops->info_get(handle, i);
>>> +		sensor = sensor_ops->info_get(handle, i);
>>>    		if (!sensor)
>>>    			continue;
>>> @@ -258,6 +264,13 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
>>>    	return PTR_ERR_OR_ZERO(hwdev);
>>>    }
>>> +static void scmi_hwmon_remove(struct scmi_device *sdev)
>>> +{
>>> +	const struct scmi_handle *handle = sdev->handle;
>>> +
>>> +	handle->put_ops(handle, SCMI_PROTOCOL_SENSOR);
>>> +}
>>> +
>>>    static const struct scmi_device_id scmi_id_table[] = {
>>>    	{ SCMI_PROTOCOL_SENSOR, "hwmon" },
>>>    	{ },
>>> @@ -267,6 +280,7 @@ MODULE_DEVICE_TABLE(scmi, scmi_id_table);
>>>    static struct scmi_driver scmi_hwmon_drv = {
>>>    	.name		= "scmi-hwmon",
>>>    	.probe		= scmi_hwmon_probe,
>>> +	.remove		= scmi_hwmon_remove,
>>>    	.id_table	= scmi_id_table,
>>>    };
>>>    module_scmi_driver(scmi_hwmon_drv);
>>> diff --git a/drivers/reset/reset-scmi.c b/drivers/reset/reset-scmi.c
>>> index 8d3a858e3b19..e48220dedb35 100644
>>> --- a/drivers/reset/reset-scmi.c
>>> +++ b/drivers/reset/reset-scmi.c
>>> @@ -2,7 +2,7 @@
>>>    /*
>>>     * ARM System Control and Management Interface (ARM SCMI) reset driver
>>>     *
>>> - * Copyright (C) 2019 ARM Ltd.
>>> + * Copyright (C) 2019-2020 ARM Ltd.
>>>     */
>>>    #include <linux/module.h>
>>> @@ -11,6 +11,8 @@
>>>    #include <linux/reset-controller.h>
>>>    #include <linux/scmi_protocol.h>
>>> +static const struct scmi_reset_ops *reset_ops;
>>> +
>>>    /**
>>>     * struct scmi_reset_data - reset controller information structure
>>>     * @rcdev: reset controller entity
>>> @@ -39,7 +41,7 @@ scmi_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
>>>    {
>>>    	const struct scmi_handle *handle = to_scmi_handle(rcdev);
>>> -	return handle->reset_ops->assert(handle, id);
>>> +	return reset_ops->assert(handle, id);
>>>    }
>>>    /**
>>> @@ -57,7 +59,7 @@ scmi_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
>>>    {
>>>    	const struct scmi_handle *handle = to_scmi_handle(rcdev);
>>> -	return handle->reset_ops->deassert(handle, id);
>>> +	return reset_ops->deassert(handle, id);
>>>    }
>>>    /**
>>> @@ -75,7 +77,7 @@ scmi_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
>>>    {
>>>    	const struct scmi_handle *handle = to_scmi_handle(rcdev);
>>> -	return handle->reset_ops->reset(handle, id);
>>> +	return reset_ops->reset(handle, id);
>>>    }
>>>    static const struct reset_control_ops scmi_reset_ops = {
>>> @@ -91,9 +93,13 @@ static int scmi_reset_probe(struct scmi_device *sdev)
>>>    	struct device_node *np = dev->of_node;
>>>    	const struct scmi_handle *handle = sdev->handle;
>>> -	if (!handle || !handle->reset_ops)
>>> +	if (!handle)
>>>    		return -ENODEV;
>>> +	reset_ops = handle->get_ops(handle, SCMI_PROTOCOL_RESET);
>>> +	if (IS_ERR(reset_ops))
>>> +		return PTR_ERR(reset_ops);
>>> +
>>>    	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>>>    	if (!data)
>>>    		return -ENOMEM;
>>> @@ -101,12 +107,19 @@ static int scmi_reset_probe(struct scmi_device *sdev)
>>>    	data->rcdev.ops = &scmi_reset_ops;
>>>    	data->rcdev.owner = THIS_MODULE;
>>>    	data->rcdev.of_node = np;
>>> -	data->rcdev.nr_resets = handle->reset_ops->num_domains_get(handle);
>>> +	data->rcdev.nr_resets = reset_ops->num_domains_get(handle);
>>>    	data->handle = handle;
>>>    	return devm_reset_controller_register(dev, &data->rcdev);
>>>    }
>>> +static void scmi_reset_remove(struct scmi_device *sdev)
>>> +{
>>> +	const struct scmi_handle *handle = sdev->handle;
>>> +
>>> +	handle->put_ops(handle, SCMI_PROTOCOL_RESET);
>>> +}
>>> +
>>>    static const struct scmi_device_id scmi_id_table[] = {
>>>    	{ SCMI_PROTOCOL_RESET, "reset" },
>>>    	{ },
>>> @@ -116,6 +129,7 @@ MODULE_DEVICE_TABLE(scmi, scmi_id_table);
>>>    static struct scmi_driver scmi_reset_driver = {
>>>    	.name = "scmi-reset",
>>>    	.probe = scmi_reset_probe,
>>> +	.remove = scmi_reset_remove,
>>>    	.id_table = scmi_id_table,
>>>    };
>>>    module_scmi_driver(scmi_reset_driver);
>>> diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
>>> index bc4f06d46bfb..bfe7017cff19 100644
>>> --- a/include/linux/scmi_protocol.h
>>> +++ b/include/linux/scmi_protocol.h
>>> @@ -257,11 +257,6 @@ struct scmi_notify_ops {
>>>     *
>>>     * @dev: pointer to the SCMI device
>>>     * @version: pointer to the structure containing SCMI version information
>>> - * @power_ops: pointer to set of power protocol operations
>>> - * @perf_ops: pointer to set of performance protocol operations
>>> - * @clk_ops: pointer to set of clock protocol operations
>>> - * @sensor_ops: pointer to set of sensor protocol operations
>>> - * @reset_ops: pointer to set of reset protocol operations
>>>     * @notify_ops: pointer to set of notifications related operations
>>>     * @notify_priv: pointer to private data structure specific to notifications
>>>     *	(for internal use only)
>>> @@ -269,11 +264,11 @@ struct scmi_notify_ops {
>>>    struct scmi_handle {
>>>    	struct device *dev;
>>>    	struct scmi_revision_info *version;
>>> -	const struct scmi_perf_ops *perf_ops;
>>> -	const struct scmi_clk_ops *clk_ops;
>>> -	const struct scmi_power_ops *power_ops;
>>> -	const struct scmi_sensor_ops *sensor_ops;
>>> -	const struct scmi_reset_ops *reset_ops;
>>> +
>>> +	const void __must_check *(*get_ops)(const struct scmi_handle *handle,
>>> +					    u8 proto);
>>> +	void (*put_ops)(const struct scmi_handle *handle, u8 proto);
>>> +
>>>    	const struct scmi_notify_ops *notify_ops;
>>>    	void *notify_priv;
>>>    };
>>>
>>
>>

-- 
Warm Regards
Thara