[PATCH v2 2/3] firmware: arm_scmi: Add Powercap protocol enable support

Cristian Marussi
2023-03-09T14:09:34Z

SCMI Powercap protocol v3.2 supports disabling the powercap on a zone
by zone basis by providing a zero valued powercap.

Expose new operations to enable/disable powercapping on a per-zone base.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
---
v1 --> v2
- simplified enable requested checks
---
drivers/firmware/arm_scmi/powercap.c | 110 +++++++++++++++++++++++++--
include/linux/scmi_protocol.h | 18 +++++
2 files changed, 122 insertions(+), 6 deletions(-)

diff --git a/drivers/firmware/arm_scmi/powercap.c b/drivers/firmware/arm_scmi/powercap.c
index 2e490492f187..244929cb4f3e 100644
--- a/drivers/firmware/arm_scmi/powercap.c
+++ b/drivers/firmware/arm_scmi/powercap.c
@@ -108,6 +108,8 @@ struct scmi_powercap_meas_changed_notify_payld {
};

struct scmi_powercap_state {
+ bool enabled;
+ u32 last_pcap;
bool meas_notif_enabled;
u64 thresholds;
#define THRESH_LOW(p, id) \
@@ -412,6 +414,10 @@ static int __scmi_powercap_cap_set(const struct scmi_protocol_handle *ph,
ignore_dresp);
}

+ /* Save the last explicitly set non-zero powercap value */
+ if (PROTOCOL_REV_MAJOR(pi->version) >= 0x2 && !ret && power_cap)
+ pi->states[domain_id].last_pcap = power_cap;
+
return ret;
}

@@ -421,6 +427,20 @@ static int scmi_powercap_cap_set(const struct scmi_protocol_handle *ph,
{
struct powercap_info *pi = ph->get_priv(ph);

+ /*
+ * Disallow zero as a possible explicitly requested powercap:
+ * there are enable/disable operations for this.
+ */
+ if (!power_cap)
+ return -EINVAL;
+
+ /* Just log the last set request if acting on a disabled domain */
+ if (PROTOCOL_REV_MAJOR(pi->version) >= 0x2 &&
+ !pi->states[domain_id].enabled) {
+ pi->states[domain_id].last_pcap = power_cap;
+ return 0;
+ }
+
return __scmi_powercap_cap_set(ph, pi, domain_id,
power_cap, ignore_dresp);
}
@@ -589,11 +609,78 @@ scmi_powercap_measurements_threshold_set(const struct scmi_protocol_handle *ph,
return ret;
}

+static int scmi_powercap_cap_enable_set(const struct scmi_protocol_handle *ph,
+ u32 domain_id, bool enable)
+{
+ int ret;
+ u32 power_cap;
+ struct powercap_info *pi = ph->get_priv(ph);
+
+ if (PROTOCOL_REV_MAJOR(pi->version) < 0x2)
+ return -EINVAL;
+
+ if (enable == pi->states[domain_id].enabled)
+ return 0;
+
+ if (enable) {
+ /* Cannot enable with a zero powercap. */
+ if (!pi->states[domain_id].last_pcap)
+ return -EINVAL;
+
+ ret = __scmi_powercap_cap_set(ph, pi, domain_id,
+ pi->states[domain_id].last_pcap,
+ true);
+ } else {
+ ret = __scmi_powercap_cap_set(ph, pi, domain_id, 0, true);
+ }
+
+ if (ret)
+ return ret;
+
+ /*
+ * Update our internal state to reflect final platform state: the SCMI
+ * server could have ignored a disable request and kept enforcing some
+ * powercap limit requested by other agents.
+ */
+ ret = scmi_powercap_cap_get(ph, domain_id, &power_cap);
+ if (!ret)
+ pi->states[domain_id].enabled = !!power_cap;
+
+ return ret;
+}
+
+static int scmi_powercap_cap_enable_get(const struct scmi_protocol_handle *ph,
+ u32 domain_id, bool *enable)
+{
+ int ret;
+ u32 power_cap;
+ struct powercap_info *pi = ph->get_priv(ph);
+
+ *enable = true;
+ if (PROTOCOL_REV_MAJOR(pi->version) < 0x2)
+ return 0;
+
+ /*
+ * Report always real platform state; platform could have ignored
+ * a previous disable request. Default true on any error.
+ */
+ ret = scmi_powercap_cap_get(ph, domain_id, &power_cap);
+ if (!ret)
+ *enable = !!power_cap;
+
+ /* Update internal state with current real platform state */
+ pi->states[domain_id].enabled = *enable;
+
+ return 0;
+}
+
static const struct scmi_powercap_proto_ops powercap_proto_ops = {
.num_domains_get = scmi_powercap_num_domains_get,
.info_get = scmi_powercap_dom_info_get,
.cap_get = scmi_powercap_cap_get,
.cap_set = scmi_powercap_cap_set,
+ .cap_enable_set = scmi_powercap_cap_enable_set,
+ .cap_enable_get = scmi_powercap_cap_enable_get,
.pai_get = scmi_powercap_pai_get,
.pai_set = scmi_powercap_pai_set,
.measurements_get = scmi_powercap_measurements_get,
@@ -854,6 +941,11 @@ scmi_powercap_protocol_init(const struct scmi_protocol_handle *ph)
if (!pinfo->powercaps)
return -ENOMEM;

+ pinfo->states = devm_kcalloc(ph->dev, pinfo->num_domains,
+ sizeof(*pinfo->states), GFP_KERNEL);
+ if (!pinfo->states)
+ return -ENOMEM;
+
/*
* Note that any failure in retrieving any domain attribute leads to
* the whole Powercap protocol initialization failure: this way the
@@ -868,15 +960,21 @@ scmi_powercap_protocol_init(const struct scmi_protocol_handle *ph)
if (pinfo->powercaps[domain].fastchannels)
scmi_powercap_domain_init_fc(ph, domain,
&pinfo->powercaps[domain].fc_info);
- }

- pinfo->states = devm_kcalloc(ph->dev, pinfo->num_domains,
- sizeof(*pinfo->states), GFP_KERNEL);
- if (!pinfo->states)
- return -ENOMEM;
+ /* Grab initial state when disable is supported. */
+ if (PROTOCOL_REV_MAJOR(version) >= 0x2) {
+ ret = __scmi_powercap_cap_get(ph,
+ &pinfo->powercaps[domain],
+ &pinfo->states[domain].last_pcap);
+ if (ret)
+ return ret;

- pinfo->version = version;
+ pinfo->states[domain].enabled =
+ !!pinfo->states[domain].last_pcap;
+ }
+ }

+ pinfo->version = version;
return ph->set_priv(ph, pinfo);
}

diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 0ce5746a4470..e6fe4f73ffe6 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -629,11 +629,25 @@ struct scmi_powercap_info {
* @num_domains_get: get the count of powercap domains provided by SCMI.
* @info_get: get the information for the specified domain.
* @cap_get: get the current CAP value for the specified domain.
+ * On SCMI platforms supporting powercap zone disabling, this could
+ * report a zero value for a zone where powercapping is disabled.
* @cap_set: set the CAP value for the specified domain to the provided value;
* if the domain supports setting the CAP with an asynchronous command
* this request will finally trigger an asynchronous transfer, but, if
* @ignore_dresp here is set to true, this call will anyway return
* immediately without waiting for the related delayed response.
+ * Note that the powercap requested value must NOT be zero, even if
+ * the platform supports disabling a powercap by setting its cap to
+ * zero (since SCMI v3.2): there are dedicated operations that should
+ * be used for that. (@cap_enable_set/get)
+ * @cap_enable_set: enable or disable the powercapping on the specified domain,
+ * if supported by the SCMI platform implementation.
+ * Note that, by the SCMI specification, the platform can
+ * silently ignore our disable request and decide to enforce
+ * anyway some other powercap value requested by another agent
+ * on the system: for this reason @cap_get and @cap_enable_get
+ * will always report the final platform view of the powercaps.
+ * @cap_enable_get: get the current CAP enable status for the specified domain.
* @pai_get: get the current PAI value for the specified domain.
* @pai_set: set the PAI value for the specified domain to the provided value.
* @measurements_get: retrieve the current average power measurements for the
@@ -662,6 +676,10 @@ struct scmi_powercap_proto_ops {
u32 *power_cap);
int (*cap_set)(const struct scmi_protocol_handle *ph, u32 domain_id,
u32 power_cap, bool ignore_dresp);
+ int (*cap_enable_set)(const struct scmi_protocol_handle *ph,
+ u32 domain_id, bool enable);
+ int (*cap_enable_get)(const struct scmi_protocol_handle *ph,
+ u32 domain_id, bool *enable);
int (*pai_get)(const struct scmi_protocol_handle *ph, u32 domain_id,
u32 *pai);
int (*pai_set)(const struct scmi_protocol_handle *ph, u32 domain_id,
--
2.34.1