diff mbox series

[v5,1/5] firmware: arm_scmi: Add Voltage Domain Support

Message ID 20201117123415.55105-2-cristian.marussi@arm.com (mailing list archive)
State New, archived
Headers show
Series Add support for SCMIv3.0 Voltage Domain Protocol and SCMI-Regulator | expand

Commit Message

Cristian Marussi Nov. 17, 2020, 12:34 p.m. UTC 
Add SCMI Voltage Domain protocol support.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v4 --> v5
- removed inline
- moved segmented intervals defines
- fixed some macros complaints by checkpatch

v3 --> v4
- avoid fixed sized typing in voltage_info
- avoid coccinelle falde complaints about pointer-sized allocations

v2 --> v3
- restrict segmented voltage domain descriptors to one triplet
- removed unneeded inline
- free allocated resources for invalid voltage domain
- added __must_check to info_get voltage operations
- added a few comments
- removed fixed size typing from struct voltage_info

v1 --> v2
- fix voltage levels query loop to reload full cmd description
  between iterations as reported by Etienne Carriere
- ensure rx buffer is properly sized calli scmi_reset_rx_to_maxsz
  between transfers
---
 drivers/firmware/arm_scmi/Makefile  |   2 +-
 drivers/firmware/arm_scmi/common.h  |   1 +
 drivers/firmware/arm_scmi/driver.c  |   2 +
 drivers/firmware/arm_scmi/voltage.c | 397 ++++++++++++++++++++++++++++
 include/linux/scmi_protocol.h       |  64 +++++
 5 files changed, 465 insertions(+), 1 deletion(-)
 create mode 100644 drivers/firmware/arm_scmi/voltage.c

Comments

Sudeep Holla Nov. 19, 2020, 4:08 p.m. UTC | #1 
On Tue, Nov 17, 2020 at 12:34:11PM +0000, Cristian Marussi wrote:
> Add SCMI Voltage Domain protocol support.
> 
> Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> ---
> v4 --> v5
> - removed inline
> - moved segmented intervals defines
> - fixed some macros complaints by checkpatch
> 
> v3 --> v4
> - avoid fixed sized typing in voltage_info
> - avoid coccinelle falde complaints about pointer-sized allocations
> 
> v2 --> v3
> - restrict segmented voltage domain descriptors to one triplet
> - removed unneeded inline
> - free allocated resources for invalid voltage domain
> - added __must_check to info_get voltage operations
> - added a few comments
> - removed fixed size typing from struct voltage_info
> 
> v1 --> v2
> - fix voltage levels query loop to reload full cmd description
>   between iterations as reported by Etienne Carriere
> - ensure rx buffer is properly sized calli scmi_reset_rx_to_maxsz
>   between transfers
> ---
>  drivers/firmware/arm_scmi/Makefile  |   2 +-
>  drivers/firmware/arm_scmi/common.h  |   1 +
>  drivers/firmware/arm_scmi/driver.c  |   2 +
>  drivers/firmware/arm_scmi/voltage.c | 397 ++++++++++++++++++++++++++++
>  include/linux/scmi_protocol.h       |  64 +++++
>  5 files changed, 465 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/firmware/arm_scmi/voltage.c
> 
> diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
> index bc0d54f8e861..6a2ef63306d6 100644
> --- a/drivers/firmware/arm_scmi/Makefile
> +++ b/drivers/firmware/arm_scmi/Makefile
> @@ -4,7 +4,7 @@ scmi-driver-y = driver.o notify.o
>  scmi-transport-y = shmem.o
>  scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
>  scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
> -scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
> +scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
>  scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
>  		    $(scmi-transport-y)
>  obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o
> diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> index 65063fa948d4..c0fb45e7c3e8 100644
> --- a/drivers/firmware/arm_scmi/common.h
> +++ b/drivers/firmware/arm_scmi/common.h
> @@ -169,6 +169,7 @@ DECLARE_SCMI_REGISTER_UNREGISTER(perf);
>  DECLARE_SCMI_REGISTER_UNREGISTER(power);
>  DECLARE_SCMI_REGISTER_UNREGISTER(reset);
>  DECLARE_SCMI_REGISTER_UNREGISTER(sensors);
> +DECLARE_SCMI_REGISTER_UNREGISTER(voltage);
>  DECLARE_SCMI_REGISTER_UNREGISTER(system);
>  
>  #define DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(id, name) \
> diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> index 3dfd8b6a0ebf..ada35e63feae 100644
> --- a/drivers/firmware/arm_scmi/driver.c
> +++ b/drivers/firmware/arm_scmi/driver.c
> @@ -946,6 +946,7 @@ static int __init scmi_driver_init(void)
>  	scmi_power_register();
>  	scmi_reset_register();
>  	scmi_sensors_register();
> +	scmi_voltage_register();
>  	scmi_system_register();
>  
>  	return platform_driver_register(&scmi_driver);
> @@ -961,6 +962,7 @@ static void __exit scmi_driver_exit(void)
>  	scmi_power_unregister();
>  	scmi_reset_unregister();
>  	scmi_sensors_unregister();
> +	scmi_voltage_unregister();
>  	scmi_system_unregister();
>  
>  	platform_driver_unregister(&scmi_driver);
> diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
> new file mode 100644
> index 000000000000..6b71589e0846
> --- /dev/null
> +++ b/drivers/firmware/arm_scmi/voltage.c
> @@ -0,0 +1,397 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * System Control and Management Interface (SCMI) Voltage Protocol
> + *
> + * Copyright (C) 2020 ARM Ltd.
> + */
> +
> +#include <linux/scmi_protocol.h>
> +
> +#include "common.h"
> +
> +#define VOLTAGE_DOMS_NUM_MASK		GENMASK(15, 0)
> +#define REMAINING_LEVELS_MASK		GENMASK(31, 16)
> +#define RETURNED_LEVELS_MASK		GENMASK(11, 0)
> +
> +enum scmi_voltage_protocol_cmd {
> +	VOLTAGE_DOMAIN_ATTRIBUTES = 0x3,
> +	VOLTAGE_DESCRIBE_LEVELS = 0x4,
> +	VOLTAGE_CONFIG_SET = 0x5,
> +	VOLTAGE_CONFIG_GET = 0x6,
> +	VOLTAGE_LEVEL_SET = 0x7,
> +	VOLTAGE_LEVEL_GET = 0x8,
> +};
> +
> +struct scmi_msg_resp_protocol_attributes {
> +	__le32 attr;
> +#define NUM_VOLTAGE_DOMAINS(x)	((u16)(FIELD_GET(VOLTAGE_DOMS_NUM_MASK, (x))))
> +};
> +

Sorry but same annoying comment again, drop one element structures.

> +struct scmi_msg_resp_domain_attributes {
> +	__le32 attr;
> +	u8 name[SCMI_MAX_STR_SIZE];
> +};
> +
> +struct scmi_msg_cmd_describe_levels {
> +	__le32 domain_id;
> +	__le32 level_index;
> +};
> +
> +struct scmi_msg_resp_describe_levels {
> +	__le32 flags;
> +#define NUM_REMAINING_LEVELS(f)	((u16)(FIELD_GET(REMAINING_LEVELS_MASK, (f))))
> +#define NUM_RETURNED_LEVELS(f)	((u16)(FIELD_GET(RETURNED_LEVELS_MASK, (f))))
> +#define SUPPORTS_SEGMENTED_LEVELS(f)	((f) & BIT(12))
> +	__le32 voltage[];
> +};
> +
> +struct scmi_msg_cmd_config_set {
> +	__le32 domain_id;
> +	__le32 config;
> +};
> +
> +struct scmi_msg_cmd_level_set {
> +	__le32 domain_id;
> +	__le32 flags;
> +	__le32 voltage_level;
> +};
> +
> +struct voltage_info {
> +	unsigned int version;
> +	unsigned int num_domains;
> +	struct scmi_voltage_info **domains;
> +};
> +
> +static int scmi_protocol_attributes_get(const struct scmi_handle *handle,
> +					struct voltage_info *vinfo)
> +{
> +	int ret;
> +	struct scmi_xfer *t;
> +	struct scmi_msg_resp_protocol_attributes *resp;
> +
> +	ret = scmi_xfer_get_init(handle, PROTOCOL_ATTRIBUTES,
> +				 SCMI_PROTOCOL_VOLTAGE, 0, sizeof(*resp), &t);
> +	if (ret)
> +		return ret;
> +
> +	resp = t->rx.buf;
> +	ret = scmi_do_xfer(handle, t);
> +	if (!ret)
> +		vinfo->num_domains =
> +			NUM_VOLTAGE_DOMAINS(le32_to_cpu(resp->attr));
> +
> +	scmi_xfer_put(handle, t);
> +	return ret;
> +}
> +
> +static int scmi_init_voltage_levels(struct device *dev,
> +				    struct scmi_voltage_info *v,
> +				    u32 flags, u32 num_returned,
> +				    u32 num_remaining)
> +{
> +	bool segmented;
> +	u32 num_levels;
> +

Why can't you pass the above 2 directly from the caller to this function
since they are just used to obtain them here.


[...]

> +static int scmi_voltage_descriptors_get(const struct scmi_handle *handle,
> +					struct voltage_info *vinfo)
> +{
> +	int ret, dom;
> +	struct scmi_xfer *td, *tl;
> +	struct device *dev = handle->dev;
> +	struct scmi_msg_resp_domain_attributes *resp_dom;
> +	struct scmi_msg_resp_describe_levels *resp_levels;
> +
> +	ret = scmi_xfer_get_init(handle, VOLTAGE_DOMAIN_ATTRIBUTES,
> +				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le32),
> +				 sizeof(*resp_dom), &td);
> +	if (ret)
> +		return ret;
> +	resp_dom = td->rx.buf;
> +
> +	ret = scmi_xfer_get_init(handle, VOLTAGE_DESCRIBE_LEVELS,
> +				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le64), 0, &tl);
> +	if (ret)
> +		goto outd;
> +	resp_levels = tl->rx.buf;
> +
> +	for (dom = 0; dom < vinfo->num_domains; dom++) {
> +		u32 desc_index = 0;
> +		u16 num_returned = 0, num_remaining = 0;
> +		struct scmi_msg_cmd_describe_levels *cmd;
> +		struct scmi_voltage_info *v;
> +
> +		/* Retrieve domain attributes at first ... */
> +		put_unaligned_le32(dom, td->tx.buf);
> +		ret = scmi_do_xfer(handle, td);
> +		/* Skip domain on comms error */
> +		if (ret)
> +			continue;
> +
> +		v = devm_kzalloc(dev, sizeof(*v), GFP_KERNEL);
> +		if (!v) {
> +			ret = -ENOMEM;
> +			break;
> +		}
> +

Why can't we allocate vinfo->domains real structure instead of pointers
and indirection there ? I understand that it helps to manage holes easily
but I think that would simplify the dynamic allocation and error handling.
It doesn't have to be this complicated(not much but still) IMO.

May be scmi_voltage_info_get can use num_levels to either return NULL
or vinfo->domains[domain_id] ?

Regards,
Sudeep
Cristian Marussi Nov. 19, 2020, 7:01 p.m. UTC | #2 
Hi Sudeep

thanks for reviewing.

On Thu, Nov 19, 2020 at 04:08:24PM +0000, Sudeep Holla wrote:
> On Tue, Nov 17, 2020 at 12:34:11PM +0000, Cristian Marussi wrote:
> > Add SCMI Voltage Domain protocol support.
> > 
> > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> > ---
> > v4 --> v5
> > - removed inline
> > - moved segmented intervals defines
> > - fixed some macros complaints by checkpatch
> > 
> > v3 --> v4
> > - avoid fixed sized typing in voltage_info
> > - avoid coccinelle falde complaints about pointer-sized allocations
> > 
> > v2 --> v3
> > - restrict segmented voltage domain descriptors to one triplet
> > - removed unneeded inline
> > - free allocated resources for invalid voltage domain
> > - added __must_check to info_get voltage operations
> > - added a few comments
> > - removed fixed size typing from struct voltage_info
> > 
> > v1 --> v2
> > - fix voltage levels query loop to reload full cmd description
> >   between iterations as reported by Etienne Carriere
> > - ensure rx buffer is properly sized calli scmi_reset_rx_to_maxsz
> >   between transfers
> > ---
> >  drivers/firmware/arm_scmi/Makefile  |   2 +-
> >  drivers/firmware/arm_scmi/common.h  |   1 +
> >  drivers/firmware/arm_scmi/driver.c  |   2 +
> >  drivers/firmware/arm_scmi/voltage.c | 397 ++++++++++++++++++++++++++++
> >  include/linux/scmi_protocol.h       |  64 +++++
> >  5 files changed, 465 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/firmware/arm_scmi/voltage.c
> > 
> > diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
> > index bc0d54f8e861..6a2ef63306d6 100644
> > --- a/drivers/firmware/arm_scmi/Makefile
> > +++ b/drivers/firmware/arm_scmi/Makefile
> > @@ -4,7 +4,7 @@ scmi-driver-y = driver.o notify.o
> >  scmi-transport-y = shmem.o
> >  scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
> >  scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
> > -scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
> > +scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
> >  scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
> >  		    $(scmi-transport-y)
> >  obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o
> > diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> > index 65063fa948d4..c0fb45e7c3e8 100644
> > --- a/drivers/firmware/arm_scmi/common.h
> > +++ b/drivers/firmware/arm_scmi/common.h
> > @@ -169,6 +169,7 @@ DECLARE_SCMI_REGISTER_UNREGISTER(perf);
> >  DECLARE_SCMI_REGISTER_UNREGISTER(power);
> >  DECLARE_SCMI_REGISTER_UNREGISTER(reset);
> >  DECLARE_SCMI_REGISTER_UNREGISTER(sensors);
> > +DECLARE_SCMI_REGISTER_UNREGISTER(voltage);
> >  DECLARE_SCMI_REGISTER_UNREGISTER(system);
> >  
> >  #define DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(id, name) \
> > diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
> > index 3dfd8b6a0ebf..ada35e63feae 100644
> > --- a/drivers/firmware/arm_scmi/driver.c
> > +++ b/drivers/firmware/arm_scmi/driver.c
> > @@ -946,6 +946,7 @@ static int __init scmi_driver_init(void)
> >  	scmi_power_register();
> >  	scmi_reset_register();
> >  	scmi_sensors_register();
> > +	scmi_voltage_register();
> >  	scmi_system_register();
> >  
> >  	return platform_driver_register(&scmi_driver);
> > @@ -961,6 +962,7 @@ static void __exit scmi_driver_exit(void)
> >  	scmi_power_unregister();
> >  	scmi_reset_unregister();
> >  	scmi_sensors_unregister();
> > +	scmi_voltage_unregister();
> >  	scmi_system_unregister();
> >  
> >  	platform_driver_unregister(&scmi_driver);
> > diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
> > new file mode 100644
> > index 000000000000..6b71589e0846
> > --- /dev/null
> > +++ b/drivers/firmware/arm_scmi/voltage.c
> > @@ -0,0 +1,397 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * System Control and Management Interface (SCMI) Voltage Protocol
> > + *
> > + * Copyright (C) 2020 ARM Ltd.
> > + */
> > +
> > +#include <linux/scmi_protocol.h>
> > +
> > +#include "common.h"
> > +
> > +#define VOLTAGE_DOMS_NUM_MASK		GENMASK(15, 0)
> > +#define REMAINING_LEVELS_MASK		GENMASK(31, 16)
> > +#define RETURNED_LEVELS_MASK		GENMASK(11, 0)
> > +
> > +enum scmi_voltage_protocol_cmd {
> > +	VOLTAGE_DOMAIN_ATTRIBUTES = 0x3,
> > +	VOLTAGE_DESCRIBE_LEVELS = 0x4,
> > +	VOLTAGE_CONFIG_SET = 0x5,
> > +	VOLTAGE_CONFIG_GET = 0x6,
> > +	VOLTAGE_LEVEL_SET = 0x7,
> > +	VOLTAGE_LEVEL_GET = 0x8,
> > +};
> > +
> > +struct scmi_msg_resp_protocol_attributes {
> > +	__le32 attr;
> > +#define NUM_VOLTAGE_DOMAINS(x)	((u16)(FIELD_GET(VOLTAGE_DOMS_NUM_MASK, (x))))
> > +};
> > +
> 
> Sorry but same annoying comment again, drop one element structures.
> 

I'll do.

> > +struct scmi_msg_resp_domain_attributes {
> > +	__le32 attr;
> > +	u8 name[SCMI_MAX_STR_SIZE];
> > +};
> > +
> > +struct scmi_msg_cmd_describe_levels {
> > +	__le32 domain_id;
> > +	__le32 level_index;
> > +};
> > +
> > +struct scmi_msg_resp_describe_levels {
> > +	__le32 flags;
> > +#define NUM_REMAINING_LEVELS(f)	((u16)(FIELD_GET(REMAINING_LEVELS_MASK, (f))))
> > +#define NUM_RETURNED_LEVELS(f)	((u16)(FIELD_GET(RETURNED_LEVELS_MASK, (f))))
> > +#define SUPPORTS_SEGMENTED_LEVELS(f)	((f) & BIT(12))
> > +	__le32 voltage[];
> > +};
> > +
> > +struct scmi_msg_cmd_config_set {
> > +	__le32 domain_id;
> > +	__le32 config;
> > +};
> > +
> > +struct scmi_msg_cmd_level_set {
> > +	__le32 domain_id;
> > +	__le32 flags;
> > +	__le32 voltage_level;
> > +};
> > +
> > +struct voltage_info {
> > +	unsigned int version;
> > +	unsigned int num_domains;
> > +	struct scmi_voltage_info **domains;
> > +};
> > +
> > +static int scmi_protocol_attributes_get(const struct scmi_handle *handle,
> > +					struct voltage_info *vinfo)
> > +{
> > +	int ret;
> > +	struct scmi_xfer *t;
> > +	struct scmi_msg_resp_protocol_attributes *resp;
> > +
> > +	ret = scmi_xfer_get_init(handle, PROTOCOL_ATTRIBUTES,
> > +				 SCMI_PROTOCOL_VOLTAGE, 0, sizeof(*resp), &t);
> > +	if (ret)
> > +		return ret;
> > +
> > +	resp = t->rx.buf;
> > +	ret = scmi_do_xfer(handle, t);
> > +	if (!ret)
> > +		vinfo->num_domains =
> > +			NUM_VOLTAGE_DOMAINS(le32_to_cpu(resp->attr));
> > +
> > +	scmi_xfer_put(handle, t);
> > +	return ret;
> > +}
> > +
> > +static int scmi_init_voltage_levels(struct device *dev,
> > +				    struct scmi_voltage_info *v,
> > +				    u32 flags, u32 num_returned,
> > +				    u32 num_remaining)
> > +{
> > +	bool segmented;
> > +	u32 num_levels;
> > +
> 
> Why can't you pass the above 2 directly from the caller to this function
> since they are just used to obtain them here.
> 

I can and I'll do for segmented, num_levels I need to have it split in
returned and remaining here to check the holy triplet is fine.
(assuming I want to keep all the checkery inside this func)

> 
> [...]
> 
> > +static int scmi_voltage_descriptors_get(const struct scmi_handle *handle,
> > +					struct voltage_info *vinfo)
> > +{
> > +	int ret, dom;
> > +	struct scmi_xfer *td, *tl;
> > +	struct device *dev = handle->dev;
> > +	struct scmi_msg_resp_domain_attributes *resp_dom;
> > +	struct scmi_msg_resp_describe_levels *resp_levels;
> > +
> > +	ret = scmi_xfer_get_init(handle, VOLTAGE_DOMAIN_ATTRIBUTES,
> > +				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le32),
> > +				 sizeof(*resp_dom), &td);
> > +	if (ret)
> > +		return ret;
> > +	resp_dom = td->rx.buf;
> > +
> > +	ret = scmi_xfer_get_init(handle, VOLTAGE_DESCRIBE_LEVELS,
> > +				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le64), 0, &tl);
> > +	if (ret)
> > +		goto outd;
> > +	resp_levels = tl->rx.buf;
> > +
> > +	for (dom = 0; dom < vinfo->num_domains; dom++) {
> > +		u32 desc_index = 0;
> > +		u16 num_returned = 0, num_remaining = 0;
> > +		struct scmi_msg_cmd_describe_levels *cmd;
> > +		struct scmi_voltage_info *v;
> > +
> > +		/* Retrieve domain attributes at first ... */
> > +		put_unaligned_le32(dom, td->tx.buf);
> > +		ret = scmi_do_xfer(handle, td);
> > +		/* Skip domain on comms error */
> > +		if (ret)
> > +			continue;
> > +
> > +		v = devm_kzalloc(dev, sizeof(*v), GFP_KERNEL);
> > +		if (!v) {
> > +			ret = -ENOMEM;
> > +			break;
> > +		}
> > +
> 
> Why can't we allocate vinfo->domains real structure instead of pointers
> and indirection there ? I understand that it helps to manage holes easily
> but I think that would simplify the dynamic allocation and error handling.
> It doesn't have to be this complicated(not much but still) IMO.
> 
> May be scmi_voltage_info_get can use num_levels to either return NULL
> or vinfo->domains[domain_id] ?
> 

Yes it was for the holes, but I'll do allocating contiguously and
checking on num_levels != 0 as you suggested

Thanks

Cristian

> Regards,
> Sudeep
diff mbox series

Patch

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index bc0d54f8e861..6a2ef63306d6 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -4,7 +4,7 @@  scmi-driver-y = driver.o notify.o
 scmi-transport-y = shmem.o
 scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
 scmi-transport-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smc.o
-scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o
+scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o system.o voltage.o
 scmi-module-objs := $(scmi-bus-y) $(scmi-driver-y) $(scmi-protocols-y) \
 		    $(scmi-transport-y)
 obj-$(CONFIG_ARM_SCMI_PROTOCOL) += scmi-module.o
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 65063fa948d4..c0fb45e7c3e8 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -169,6 +169,7 @@  DECLARE_SCMI_REGISTER_UNREGISTER(perf);
 DECLARE_SCMI_REGISTER_UNREGISTER(power);
 DECLARE_SCMI_REGISTER_UNREGISTER(reset);
 DECLARE_SCMI_REGISTER_UNREGISTER(sensors);
+DECLARE_SCMI_REGISTER_UNREGISTER(voltage);
 DECLARE_SCMI_REGISTER_UNREGISTER(system);
 
 #define DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(id, name) \
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 3dfd8b6a0ebf..ada35e63feae 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -946,6 +946,7 @@  static int __init scmi_driver_init(void)
 	scmi_power_register();
 	scmi_reset_register();
 	scmi_sensors_register();
+	scmi_voltage_register();
 	scmi_system_register();
 
 	return platform_driver_register(&scmi_driver);
@@ -961,6 +962,7 @@  static void __exit scmi_driver_exit(void)
 	scmi_power_unregister();
 	scmi_reset_unregister();
 	scmi_sensors_unregister();
+	scmi_voltage_unregister();
 	scmi_system_unregister();
 
 	platform_driver_unregister(&scmi_driver);
diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
new file mode 100644
index 000000000000..6b71589e0846
--- /dev/null
+++ b/drivers/firmware/arm_scmi/voltage.c
@@ -0,0 +1,397 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) Voltage Protocol
+ *
+ * Copyright (C) 2020 ARM Ltd.
+ */
+
+#include <linux/scmi_protocol.h>
+
+#include "common.h"
+
+#define VOLTAGE_DOMS_NUM_MASK		GENMASK(15, 0)
+#define REMAINING_LEVELS_MASK		GENMASK(31, 16)
+#define RETURNED_LEVELS_MASK		GENMASK(11, 0)
+
+enum scmi_voltage_protocol_cmd {
+	VOLTAGE_DOMAIN_ATTRIBUTES = 0x3,
+	VOLTAGE_DESCRIBE_LEVELS = 0x4,
+	VOLTAGE_CONFIG_SET = 0x5,
+	VOLTAGE_CONFIG_GET = 0x6,
+	VOLTAGE_LEVEL_SET = 0x7,
+	VOLTAGE_LEVEL_GET = 0x8,
+};
+
+struct scmi_msg_resp_protocol_attributes {
+	__le32 attr;
+#define NUM_VOLTAGE_DOMAINS(x)	((u16)(FIELD_GET(VOLTAGE_DOMS_NUM_MASK, (x))))
+};
+
+struct scmi_msg_resp_domain_attributes {
+	__le32 attr;
+	u8 name[SCMI_MAX_STR_SIZE];
+};
+
+struct scmi_msg_cmd_describe_levels {
+	__le32 domain_id;
+	__le32 level_index;
+};
+
+struct scmi_msg_resp_describe_levels {
+	__le32 flags;
+#define NUM_REMAINING_LEVELS(f)	((u16)(FIELD_GET(REMAINING_LEVELS_MASK, (f))))
+#define NUM_RETURNED_LEVELS(f)	((u16)(FIELD_GET(RETURNED_LEVELS_MASK, (f))))
+#define SUPPORTS_SEGMENTED_LEVELS(f)	((f) & BIT(12))
+	__le32 voltage[];
+};
+
+struct scmi_msg_cmd_config_set {
+	__le32 domain_id;
+	__le32 config;
+};
+
+struct scmi_msg_cmd_level_set {
+	__le32 domain_id;
+	__le32 flags;
+	__le32 voltage_level;
+};
+
+struct voltage_info {
+	unsigned int version;
+	unsigned int num_domains;
+	struct scmi_voltage_info **domains;
+};
+
+static int scmi_protocol_attributes_get(const struct scmi_handle *handle,
+					struct voltage_info *vinfo)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct scmi_msg_resp_protocol_attributes *resp;
+
+	ret = scmi_xfer_get_init(handle, PROTOCOL_ATTRIBUTES,
+				 SCMI_PROTOCOL_VOLTAGE, 0, sizeof(*resp), &t);
+	if (ret)
+		return ret;
+
+	resp = t->rx.buf;
+	ret = scmi_do_xfer(handle, t);
+	if (!ret)
+		vinfo->num_domains =
+			NUM_VOLTAGE_DOMAINS(le32_to_cpu(resp->attr));
+
+	scmi_xfer_put(handle, t);
+	return ret;
+}
+
+static int scmi_init_voltage_levels(struct device *dev,
+				    struct scmi_voltage_info *v,
+				    u32 flags, u32 num_returned,
+				    u32 num_remaining)
+{
+	bool segmented;
+	u32 num_levels;
+
+	segmented = SUPPORTS_SEGMENTED_LEVELS(flags);
+	num_levels = num_returned + num_remaining;
+	/*
+	 * segmented levels entries are represented by a single triplet
+	 * returned all in one go.
+	 */
+	if (!num_levels ||
+	    (segmented && (num_remaining || num_returned != 3))) {
+		dev_err(dev,
+			"Invalid level descriptor(%d/%d/%d) for voltage dom %d\n",
+			num_levels, num_returned, num_remaining, v->id);
+		return -EINVAL;
+	}
+
+	v->levels_uv = devm_kcalloc(dev, num_levels, sizeof(u32), GFP_KERNEL);
+	if (!v->levels_uv)
+		return -ENOMEM;
+
+	v->num_levels = num_levels;
+	v->segmented = segmented;
+
+	return 0;
+}
+
+static int scmi_voltage_descriptors_get(const struct scmi_handle *handle,
+					struct voltage_info *vinfo)
+{
+	int ret, dom;
+	struct scmi_xfer *td, *tl;
+	struct device *dev = handle->dev;
+	struct scmi_msg_resp_domain_attributes *resp_dom;
+	struct scmi_msg_resp_describe_levels *resp_levels;
+
+	ret = scmi_xfer_get_init(handle, VOLTAGE_DOMAIN_ATTRIBUTES,
+				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le32),
+				 sizeof(*resp_dom), &td);
+	if (ret)
+		return ret;
+	resp_dom = td->rx.buf;
+
+	ret = scmi_xfer_get_init(handle, VOLTAGE_DESCRIBE_LEVELS,
+				 SCMI_PROTOCOL_VOLTAGE, sizeof(__le64), 0, &tl);
+	if (ret)
+		goto outd;
+	resp_levels = tl->rx.buf;
+
+	for (dom = 0; dom < vinfo->num_domains; dom++) {
+		u32 desc_index = 0;
+		u16 num_returned = 0, num_remaining = 0;
+		struct scmi_msg_cmd_describe_levels *cmd;
+		struct scmi_voltage_info *v;
+
+		/* Retrieve domain attributes at first ... */
+		put_unaligned_le32(dom, td->tx.buf);
+		ret = scmi_do_xfer(handle, td);
+		/* Skip domain on comms error */
+		if (ret)
+			continue;
+
+		v = devm_kzalloc(dev, sizeof(*v), GFP_KERNEL);
+		if (!v) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		v->id = dom;
+		v->attributes = le32_to_cpu(resp_dom->attr);
+		strlcpy(v->name, resp_dom->name, SCMI_MAX_STR_SIZE);
+
+		cmd = tl->tx.buf;
+		/* ...then retrieve domain levels descriptions */
+		do {
+			u32 flags;
+			int cnt;
+
+			cmd->domain_id = cpu_to_le32(v->id);
+			cmd->level_index = desc_index;
+			ret = scmi_do_xfer(handle, tl);
+			if (ret)
+				break;
+
+			flags = le32_to_cpu(resp_levels->flags);
+			num_returned = NUM_RETURNED_LEVELS(flags);
+			num_remaining = NUM_REMAINING_LEVELS(flags);
+
+			/* Allocate space for num_levels if not already done */
+			if (!v->num_levels) {
+				ret = scmi_init_voltage_levels(dev, v, flags,
+							       num_returned,
+							       num_remaining);
+				if (ret)
+					break;
+			}
+
+			if (desc_index + num_returned > v->num_levels) {
+				dev_err(handle->dev,
+					"No. of voltage levels can't exceed %d\n",
+					v->num_levels);
+				ret = -EINVAL;
+				break;
+			}
+
+			for (cnt = 0; cnt < num_returned; cnt++) {
+				s32 val;
+
+				val =
+				    (s32)le32_to_cpu(resp_levels->voltage[cnt]);
+				v->levels_uv[desc_index + cnt] = val;
+				if (val < 0)
+					v->negative_volts_allowed = true;
+			}
+
+			desc_index += num_returned;
+
+			scmi_reset_rx_to_maxsz(handle, tl);
+			/* check both to avoid infinite loop due to buggy fw */
+		} while (num_returned && num_remaining);
+
+		/*
+		 * Bail out only on memory errors, just skip domain and free
+		 * on any other error.
+		 */
+		if (!ret) {
+			vinfo->domains[dom] = v;
+		} else if (ret != -ENOMEM) {
+			devm_kfree(dev, v->levels_uv);
+			devm_kfree(dev, v);
+		} else {
+			break;
+		}
+
+		scmi_reset_rx_to_maxsz(handle, td);
+	}
+
+	scmi_xfer_put(handle, tl);
+outd:
+	scmi_xfer_put(handle, td);
+
+	return ret;
+}
+
+static int __scmi_voltage_get_u32(const struct scmi_handle *handle,
+				  u8 cmd_id, u32 domain_id, u32 *value)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct voltage_info *vinfo = handle->voltage_priv;
+
+	if (domain_id >= vinfo->num_domains)
+		return -EINVAL;
+
+	ret = scmi_xfer_get_init(handle, cmd_id,
+				 SCMI_PROTOCOL_VOLTAGE,
+				 sizeof(__le32), 0, &t);
+	if (ret)
+		return ret;
+
+	put_unaligned_le32(domain_id, t->tx.buf);
+	ret = scmi_do_xfer(handle, t);
+	if (!ret)
+		*value = get_unaligned_le32(t->rx.buf);
+
+	scmi_xfer_put(handle, t);
+	return ret;
+}
+
+static int scmi_voltage_config_set(const struct scmi_handle *handle,
+				   u32 domain_id, u32 config)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct voltage_info *vinfo = handle->voltage_priv;
+	struct scmi_msg_cmd_config_set *cmd;
+
+	if (domain_id >= vinfo->num_domains)
+		return -EINVAL;
+
+	ret = scmi_xfer_get_init(handle, VOLTAGE_CONFIG_SET,
+				 SCMI_PROTOCOL_VOLTAGE,
+				 sizeof(*cmd), 0, &t);
+	if (ret)
+		return ret;
+
+	cmd = t->tx.buf;
+	cmd->domain_id = cpu_to_le32(domain_id);
+	cmd->config = cpu_to_le32(config & GENMASK(3, 0));
+
+	ret = scmi_do_xfer(handle, t);
+
+	scmi_xfer_put(handle, t);
+	return ret;
+}
+
+static int scmi_voltage_config_get(const struct scmi_handle *handle,
+				   u32 domain_id, u32 *config)
+{
+	return __scmi_voltage_get_u32(handle, VOLTAGE_CONFIG_GET,
+				      domain_id, config);
+}
+
+static int scmi_voltage_level_set(const struct scmi_handle *handle,
+				  u32 domain_id, u32 flags, s32 volt_uV)
+{
+	int ret;
+	struct scmi_xfer *t;
+	struct voltage_info *vinfo = handle->voltage_priv;
+	struct scmi_msg_cmd_level_set *cmd;
+
+	if (domain_id >= vinfo->num_domains)
+		return -EINVAL;
+
+	ret = scmi_xfer_get_init(handle, VOLTAGE_LEVEL_SET,
+				 SCMI_PROTOCOL_VOLTAGE,
+				 sizeof(*cmd), 0, &t);
+	if (ret)
+		return ret;
+
+	cmd = t->tx.buf;
+	cmd->domain_id = cpu_to_le32(domain_id);
+	cmd->flags = cpu_to_le32(flags);
+	cmd->voltage_level = cpu_to_le32(volt_uV);
+
+	ret = scmi_do_xfer(handle, t);
+
+	scmi_xfer_put(handle, t);
+	return ret;
+}
+
+static int scmi_voltage_level_get(const struct scmi_handle *handle,
+				  u32 domain_id, s32 *volt_uV)
+{
+	return __scmi_voltage_get_u32(handle, VOLTAGE_LEVEL_GET,
+				      domain_id, (u32 *)volt_uV);
+}
+
+static const struct scmi_voltage_info * __must_check
+scmi_voltage_info_get(const struct scmi_handle *handle, u32 domain_id)
+{
+	struct voltage_info *vinfo = handle->voltage_priv;
+
+	if (domain_id >= vinfo->num_domains)
+		return NULL;
+
+	return vinfo->domains[domain_id];
+}
+
+static int scmi_voltage_domains_num_get(const struct scmi_handle *handle)
+{
+	struct voltage_info *vinfo = handle->voltage_priv;
+
+	return vinfo->num_domains;
+}
+
+static struct scmi_voltage_ops voltage_ops = {
+	.num_domains_get = scmi_voltage_domains_num_get,
+	.info_get = scmi_voltage_info_get,
+	.config_set = scmi_voltage_config_set,
+	.config_get = scmi_voltage_config_get,
+	.level_set = scmi_voltage_level_set,
+	.level_get = scmi_voltage_level_get,
+};
+
+static int scmi_voltage_protocol_init(struct scmi_handle *handle)
+{
+	int ret;
+	u32 version;
+	struct voltage_info *vinfo;
+
+	ret = scmi_version_get(handle, SCMI_PROTOCOL_VOLTAGE, &version);
+	if (ret)
+		return ret;
+
+	dev_dbg(handle->dev, "Voltage Version %d.%d\n",
+		PROTOCOL_REV_MAJOR(version), PROTOCOL_REV_MINOR(version));
+
+	vinfo = devm_kzalloc(handle->dev, sizeof(*vinfo), GFP_KERNEL);
+	if (!vinfo)
+		return -ENOMEM;
+	vinfo->version = version;
+
+	ret = scmi_protocol_attributes_get(handle, vinfo);
+	if (ret)
+		return ret;
+
+	if (vinfo->num_domains) {
+		vinfo->domains = devm_kcalloc(handle->dev, vinfo->num_domains,
+					      sizeof(void *), GFP_KERNEL);
+		if (!vinfo->domains)
+			return -ENOMEM;
+		ret = scmi_voltage_descriptors_get(handle, vinfo);
+		if (ret)
+			return ret;
+	} else {
+		dev_warn(handle->dev, "No Voltage domains found.\n");
+	}
+
+	handle->voltage_ops = &voltage_ops;
+	handle->voltage_priv = vinfo;
+
+	return 0;
+}
+
+DEFINE_SCMI_PROTOCOL_REGISTER_UNREGISTER(SCMI_PROTOCOL_VOLTAGE, voltage)
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 9cd312a1ff92..b11ca01e2393 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -209,6 +209,64 @@  struct scmi_reset_ops {
 	int (*deassert)(const struct scmi_handle *handle, u32 domain);
 };
 
+/**
+ * struct scmi_voltage_info - describe one available SCMI Voltage Domain
+ *
+ * @id: the domain ID as advertised by the platform
+ * @segmented: defines the layout of the entries of array @levels_uv.
+ *	       - when True the entries are to be interpreted as triplets,
+ *	         each defining a segment representing a range of equally
+ *	         space voltages: <lowest_volts>, <highest_volt>, <step_uV>
+ *	       - when False the entries simply represent a single discrete
+ *	         supported voltage level
+ * @negative_volts_allowed: True if any of the entries of @levels_uv represent
+ *			    a negative voltage.
+ * @attributes: represents Voltage Domain advertised attributes
+ * @name: name assigned to the Voltage Domain by platform
+ * @num_levels: number of total entries in @levels_uv.
+ * @levels_uv: array of entries describing the available voltage levels for
+ *	       this domain.
+ */
+struct scmi_voltage_info {
+	unsigned int id;
+	bool segmented;
+	bool negative_volts_allowed;
+	unsigned int attributes;
+	char name[SCMI_MAX_STR_SIZE];
+	unsigned int num_levels;
+#define SCMI_VOLTAGE_SEGMENT_LOW	0
+#define SCMI_VOLTAGE_SEGMENT_HIGH	1
+#define SCMI_VOLTAGE_SEGMENT_STEP	2
+	int *levels_uv;
+};
+
+/**
+ * struct scmi_voltage_ops - represents the various operations provided
+ * by SCMI Voltage Protocol
+ *
+ * @num_domains_get: get the count of voltage domains provided by SCMI
+ * @info_get: get the information of the specified domain
+ * @config_set: set the config for the specified domain
+ * @config_get: get the config of the specified domain
+ * @level_set: set the voltage level for the specified domain
+ * @level_get: get the voltage level of the specified domain
+ */
+struct scmi_voltage_ops {
+	int (*num_domains_get)(const struct scmi_handle *handle);
+	const struct scmi_voltage_info __must_check *(*info_get)
+		(const struct scmi_handle *handle, u32 domain_id);
+	int (*config_set)(const struct scmi_handle *handle, u32 domain_id,
+			  u32 config);
+#define	SCMI_VOLTAGE_ARCH_STATE_OFF		0x0
+#define	SCMI_VOLTAGE_ARCH_STATE_ON		0x7
+	int (*config_get)(const struct scmi_handle *handle, u32 domain_id,
+			  u32 *config);
+	int (*level_set)(const struct scmi_handle *handle, u32 domain_id,
+			 u32 flags, s32 volt_uV);
+	int (*level_get)(const struct scmi_handle *handle, u32 domain_id,
+			 s32 *volt_uV);
+};
+
 /**
  * struct scmi_notify_ops  - represents notifications' operations provided by
  * SCMI core
@@ -262,6 +320,7 @@  struct scmi_notify_ops {
  * @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
+ * @voltage_ops: pointer to set of voltage protocol operations
  * @notify_ops: pointer to set of notifications related operations
  * @perf_priv: pointer to private data structure specific to performance
  *	protocol(for internal use only)
@@ -273,6 +332,8 @@  struct scmi_notify_ops {
  *	protocol(for internal use only)
  * @reset_priv: pointer to private data structure specific to reset
  *	protocol(for internal use only)
+ * @voltage_priv: pointer to private data structure specific to voltage
+ *	protocol(for internal use only)
  * @notify_priv: pointer to private data structure specific to notifications
  *	(for internal use only)
  */
@@ -284,6 +345,7 @@  struct scmi_handle {
 	const struct scmi_power_ops *power_ops;
 	const struct scmi_sensor_ops *sensor_ops;
 	const struct scmi_reset_ops *reset_ops;
+	const struct scmi_voltage_ops *voltage_ops;
 	const struct scmi_notify_ops *notify_ops;
 	/* for protocol internal use */
 	void *perf_priv;
@@ -291,6 +353,7 @@  struct scmi_handle {
 	void *power_priv;
 	void *sensor_priv;
 	void *reset_priv;
+	void *voltage_priv;
 	void *notify_priv;
 	void *system_priv;
 };
@@ -303,6 +366,7 @@  enum scmi_std_protocol {
 	SCMI_PROTOCOL_CLOCK = 0x14,
 	SCMI_PROTOCOL_SENSOR = 0x15,
 	SCMI_PROTOCOL_RESET = 0x16,
+	SCMI_PROTOCOL_VOLTAGE = 0x17,
 };
 
 enum scmi_system_events {