[PATCH v2] powercap: Add Power Limit4 support

Sumeet Pawnikar
2020-07-14T08:22:12Z

Modern Intel Mobile platforms support power limit4 (PL4), which is
the SoC package level maximum power limit (in Watts). It can be used
to preemptively limits potential SoC power to prevent power spikes
from tripping the power adapter and battery over-current protection.
This patch enables this feature by exposing package level peak power
capping control to userspace via RAPL sysfs interface. With this,
application like DTPF can modify PL4 power limit, the similar way
of other package power limit (PL1).
As this feature is not tested on previous generations, here it is
enabled only for the platform that has been verified to work,
for safety concerns.

Signed-off-by: Sumeet Pawnikar <sumeet.r.pawnikar@intel.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
---
Changes in v2:
- Addressed review comments from Rafael.
- Made the commit message more clearer.
- Updated powercap documentation.
---
Documentation/power/powercap/powercap.rst | 14 +++++---
drivers/powercap/intel_rapl_common.c | 54 +++++++++++++++++++++++++++--
drivers/powercap/intel_rapl_msr.c | 15 ++++++++
include/linux/intel_rapl.h | 5 ++-
4 files changed, 80 insertions(+), 8 deletions(-)

diff --git a/Documentation/power/powercap/powercap.rst b/Documentation/power/powercap/powercap.rst
index 7ae3b44c7624..b3af059b6d5d 100644
--- a/Documentation/power/powercap/powercap.rst
+++ b/Documentation/power/powercap/powercap.rst
@@ -167,11 +167,12 @@ For example::
package-0
---------

-The Intel RAPL technology allows two constraints, short term and long term,
-with two different time windows to be applied to each power zone. Thus for
-each zone there are 2 attributes representing the constraint names, 2 power
-limits and 2 attributes representing the sizes of the time windows. Such that,
-constraint_j_* attributes correspond to the jth constraint (j = 0,1).
+Depending on different power zones, the Intel RAPL technology allows
+one or multiple constraints like short term, long term and peak power,
+with different time windows to be applied to each power zone.
+All the zones contain attributes representing the constraint names,
+power limits and the sizes of the time windows. Such that,
+constraint_j_* attributes correspond to the jth constraint (j = 0,1,2).

For example::

@@ -181,6 +182,9 @@ For example::
constraint_1_name
constraint_1_power_limit_uw
constraint_1_time_window_us
+ constraint_2_name
+ constraint_2_power_limit_uw
+ constraint_2_time_window_us

Power Zone Attributes
=====================
diff --git a/drivers/powercap/intel_rapl_common.c b/drivers/powercap/intel_rapl_common.c
index 61a63a16b5e7..a8bcc58d61f0 100644
--- a/drivers/powercap/intel_rapl_common.c
+++ b/drivers/powercap/intel_rapl_common.c
@@ -39,6 +39,8 @@
#define POWER_HIGH_LOCK BIT_ULL(63)
#define POWER_LOW_LOCK BIT(31)

+#define POWER_LIMIT4_MASK 0x1FFF
+
#define TIME_WINDOW1_MASK (0x7FULL<<17)
#define TIME_WINDOW2_MASK (0x7FULL<<49)

@@ -82,6 +84,7 @@ enum unit_type {

static const char pl1_name[] = "long_term";
static const char pl2_name[] = "short_term";
+static const char pl4_name[] = "peak_power";

#define power_zone_to_rapl_domain(_zone) \
container_of(_zone, struct rapl_domain, power_zone)
@@ -337,6 +340,9 @@ static int set_power_limit(struct powercap_zone *power_zone, int cid,
case PL2_ENABLE:
rapl_write_data_raw(rd, POWER_LIMIT2, power_limit);
break;
+ case PL4_ENABLE:
+ rapl_write_data_raw(rd, POWER_LIMIT4, power_limit);
+ break;
default:
ret = -EINVAL;
}
@@ -371,6 +377,9 @@ static int get_current_power_limit(struct powercap_zone *power_zone, int cid,
case PL2_ENABLE:
prim = POWER_LIMIT2;
break;
+ case PL4_ENABLE:
+ prim = POWER_LIMIT4;
+ break;
default:
put_online_cpus();
return -EINVAL;
@@ -440,6 +449,13 @@ static int get_time_window(struct powercap_zone *power_zone, int cid,
case PL2_ENABLE:
ret = rapl_read_data_raw(rd, TIME_WINDOW2, true, &val);
break;
+ case PL4_ENABLE:
+ /*
+ * Time window parameter is not applicable for PL4 entry
+ * so assigining '0' as default value.
+ */
+ val = 0;
+ break;
default:
put_online_cpus();
return -EINVAL;
@@ -483,6 +499,9 @@ static int get_max_power(struct powercap_zone *power_zone, int id, u64 *data)
case PL2_ENABLE:
prim = MAX_POWER;
break;
+ case PL4_ENABLE:
+ prim = MAX_POWER;
+ break;
default:
put_online_cpus();
return -EINVAL;
@@ -492,6 +511,10 @@ static int get_max_power(struct powercap_zone *power_zone, int id, u64 *data)
else
*data = val;

+ /* As a generalization rule, PL4 would be around two times PL2. */
+ if (rd->rpl[id].prim_id == PL4_ENABLE)
+ *data = *data * 2;
+
put_online_cpus();

return ret;
@@ -524,12 +547,22 @@ static void rapl_init_domains(struct rapl_package *rp)
rd->id = i;
rd->rpl[0].prim_id = PL1_ENABLE;
rd->rpl[0].name = pl1_name;
- /* some domain may support two power limits */
- if (rp->priv->limits[i] == 2) {
+
+ /*
+ * The PL2 power domain is applicable for limits two
+ * and limits three
+ */
+ if (rp->priv->limits[i] >= 2) {
rd->rpl[1].prim_id = PL2_ENABLE;
rd->rpl[1].name = pl2_name;
}

+ /* Enable PL4 domain if the total power limits are three */
+ if (rp->priv->limits[i] == 3) {
+ rd->rpl[2].prim_id = PL4_ENABLE;
+ rd->rpl[2].name = pl4_name;
+ }
+
for (j = 0; j < RAPL_DOMAIN_REG_MAX; j++)
rd->regs[j] = rp->priv->regs[i][j];

@@ -587,6 +620,8 @@ static u64 rapl_unit_xlate(struct rapl_domain *rd, enum unit_type type,
RAPL_DOMAIN_REG_LIMIT, POWER_UNIT, 0),
PRIMITIVE_INFO_INIT(POWER_LIMIT2, POWER_LIMIT2_MASK, 32,
RAPL_DOMAIN_REG_LIMIT, POWER_UNIT, 0),
+ PRIMITIVE_INFO_INIT(POWER_LIMIT4, POWER_LIMIT4_MASK, 0,
+ RAPL_DOMAIN_REG_PL4, POWER_UNIT, 0),
PRIMITIVE_INFO_INIT(FW_LOCK, POWER_LOW_LOCK, 31,
RAPL_DOMAIN_REG_LIMIT, ARBITRARY_UNIT, 0),
PRIMITIVE_INFO_INIT(PL1_ENABLE, POWER_LIMIT1_ENABLE, 15,
@@ -597,6 +632,8 @@ static u64 rapl_unit_xlate(struct rapl_domain *rd, enum unit_type type,
RAPL_DOMAIN_REG_LIMIT, ARBITRARY_UNIT, 0),
PRIMITIVE_INFO_INIT(PL2_CLAMP, POWER_LIMIT2_CLAMP, 48,
RAPL_DOMAIN_REG_LIMIT, ARBITRARY_UNIT, 0),
+ PRIMITIVE_INFO_INIT(PL4_ENABLE, POWER_LIMIT4_MASK, 0,
+ RAPL_DOMAIN_REG_PL4, ARBITRARY_UNIT, 0),
PRIMITIVE_INFO_INIT(TIME_WINDOW1, TIME_WINDOW1_MASK, 17,
RAPL_DOMAIN_REG_LIMIT, TIME_UNIT, 0),
PRIMITIVE_INFO_INIT(TIME_WINDOW2, TIME_WINDOW2_MASK, 49,
@@ -1252,6 +1289,7 @@ void rapl_remove_package(struct rapl_package *rp)
if (find_nr_power_limit(rd) > 1) {
rapl_write_data_raw(rd, PL2_ENABLE, 0);
rapl_write_data_raw(rd, PL2_CLAMP, 0);
+ rapl_write_data_raw(rd, PL4_ENABLE, 0);
}
if (rd->id == RAPL_DOMAIN_PACKAGE) {
rd_package = rd;
@@ -1360,6 +1398,13 @@ static void power_limit_state_save(void)
if (ret)
rd->rpl[i].last_power_limit = 0;
break;
+ case PL4_ENABLE:
+ ret = rapl_read_data_raw(rd,
+ POWER_LIMIT4, true,
+ &rd->rpl[i].last_power_limit);
+ if (ret)
+ rd->rpl[i].last_power_limit = 0;
+ break;
}
}
}
@@ -1390,6 +1435,11 @@ static void power_limit_state_restore(void)
rapl_write_data_raw(rd, POWER_LIMIT2,
rd->rpl[i].last_power_limit);
break;
+ case PL4_ENABLE:
+ if (rd->rpl[i].last_power_limit)
+ rapl_write_data_raw(rd, POWER_LIMIT4,
+ rd->rpl[i].last_power_limit);
+ break;
}
}
}
diff --git a/drivers/powercap/intel_rapl_msr.c b/drivers/powercap/intel_rapl_msr.c
index d5487965bdfe..83c76454623e 100644
--- a/drivers/powercap/intel_rapl_msr.c
+++ b/drivers/powercap/intel_rapl_msr.c
@@ -28,6 +28,7 @@

/* Local defines */
#define MSR_PLATFORM_POWER_LIMIT 0x0000065C
+#define MSR_VR_CURRENT_CONFIG 0x00000601

/* private data for RAPL MSR Interface */
static struct rapl_if_priv rapl_msr_priv = {
@@ -123,13 +124,27 @@ static int rapl_msr_write_raw(int cpu, struct reg_action *ra)
return ra->err;
}

+/* List of verified CPUs. */
+static const struct x86_cpu_id pl4_support_ids[] = {
+ { X86_VENDOR_INTEL, 6, INTEL_FAM6_TIGERLAKE_L, X86_FEATURE_ANY },
+ {}
+};
+
static int rapl_msr_probe(struct platform_device *pdev)
{
int ret;
+ const struct x86_cpu_id *id = x86_match_cpu(pl4_support_ids);

rapl_msr_priv.read_raw = rapl_msr_read_raw;
rapl_msr_priv.write_raw = rapl_msr_write_raw;

+ if (id) {
+ rapl_msr_priv.limits[RAPL_DOMAIN_PACKAGE] = 3;
+ rapl_msr_priv.regs[RAPL_DOMAIN_PACKAGE][RAPL_DOMAIN_REG_PL4] =
+ MSR_VR_CURRENT_CONFIG;
+ pr_info("PL4 support detected.\n");
+ }
+
rapl_msr_priv.control_type = powercap_register_control_type(NULL, "intel-rapl", NULL);
if (IS_ERR(rapl_msr_priv.control_type)) {
pr_debug("failed to register powercap control_type.\n");
diff --git a/include/linux/intel_rapl.h b/include/linux/intel_rapl.h
index efb3ce892c20..3582176a1eca 100644
--- a/include/linux/intel_rapl.h
+++ b/include/linux/intel_rapl.h
@@ -29,6 +29,7 @@ enum rapl_domain_reg_id {
RAPL_DOMAIN_REG_PERF,
RAPL_DOMAIN_REG_POLICY,
RAPL_DOMAIN_REG_INFO,
+ RAPL_DOMAIN_REG_PL4,
RAPL_DOMAIN_REG_MAX,
};

@@ -38,12 +39,14 @@ enum rapl_primitives {
ENERGY_COUNTER,
POWER_LIMIT1,
POWER_LIMIT2,
+ POWER_LIMIT4,
FW_LOCK,

PL1_ENABLE, /* power limit 1, aka long term */
PL1_CLAMP, /* allow frequency to go below OS request */
PL2_ENABLE, /* power limit 2, aka short term, instantaneous */
PL2_CLAMP,
+ PL4_ENABLE, /* power limit 4, aka max peak power */

TIME_WINDOW1, /* long term */
TIME_WINDOW2, /* short term */
@@ -65,7 +68,7 @@ struct rapl_domain_data {
unsigned long timestamp;
};

-#define NR_POWER_LIMITS (2)
+#define NR_POWER_LIMITS (3)
struct rapl_power_limit {
struct powercap_zone_constraint *constraint;
int prim_id; /* primitive ID used to enable */
--
1.7.9.5