Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over
the frequency monitor feature. The attribute uses the existing
dpll_feature_state enum (enable/disable) and is present in both
device-get reply and device-set request.
Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured
input frequency in Hz. The attribute is present in the pin-get reply.
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
---
Documentation/driver-api/dpll.rst | 18 ++++++++++++++++++
Documentation/netlink/specs/dpll.yaml | 17 +++++++++++++++++
drivers/dpll/dpll_nl.c | 5 +++--
include/uapi/linux/dpll.h | 2 ++
4 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/Documentation/driver-api/dpll.rst b/Documentation/driver-api/dpll.rst
index 83118c728ed90..f38e7012e8c0a 100644
--- a/Documentation/driver-api/dpll.rst
+++ b/Documentation/driver-api/dpll.rst
@@ -250,6 +250,22 @@ in the ``DPLL_A_PIN_PHASE_OFFSET`` attribute.
``DPLL_A_PHASE_OFFSET_MONITOR`` attr state of a feature
=============================== ========================
+Frequency monitor
+=================
+
+Some DPLL devices may offer the capability to measure the actual
+frequency of all available input pins. The attribute and current feature state
+shall be included in the response message of the ``DPLL_CMD_DEVICE_GET``
+command for supported DPLL devices. In such cases, users can also control
+the feature using the ``DPLL_CMD_DEVICE_SET`` command by setting the
+``enum dpll_feature_state`` values for the attribute.
+Once enabled the measured input frequency for each input pin shall be
+returned in the ``DPLL_A_PIN_MEASURED_FREQUENCY`` attribute.
+
+ =============================== ========================
+ ``DPLL_A_FREQUENCY_MONITOR`` attr state of a feature
+ =============================== ========================
+
Embedded SYNC
=============
@@ -411,6 +427,8 @@ according to attribute purpose.
``DPLL_A_PIN_STATE`` attr state of pin on the parent
pin
``DPLL_A_PIN_CAPABILITIES`` attr bitmask of pin capabilities
+ ``DPLL_A_PIN_MEASURED_FREQUENCY`` attr measured frequency of
+ an input pin in Hz
==================================== ==================================
==================================== =================================
diff --git a/Documentation/netlink/specs/dpll.yaml b/Documentation/netlink/specs/dpll.yaml
index 3dd48a32f7837..80292b0f2b488 100644
--- a/Documentation/netlink/specs/dpll.yaml
+++ b/Documentation/netlink/specs/dpll.yaml
@@ -319,6 +319,13 @@ attribute-sets:
name: phase-offset-avg-factor
type: u32
doc: Averaging factor applied to calculation of reported phase offset.
+ -
+ name: frequency-monitor
+ type: u32
+ enum: feature-state
+ doc: Receive or request state of frequency monitor feature.
+ If enabled, dpll device shall measure all currently available
+ inputs for their actual input frequency.
-
name: pin
enum-name: dpll_a_pin
@@ -456,6 +463,13 @@ attribute-sets:
Value is in PPT (parts per trillion, 10^-12).
Note: This attribute provides higher resolution than the standard
fractional-frequency-offset (which is in PPM).
+ -
+ name: measured-frequency
+ type: u64
+ doc: |
+ The measured frequency of the input pin in Hz.
+ This is the actual frequency being received on the pin,
+ as measured by the dpll device hardware.
-
name: pin-parent-device
@@ -544,6 +558,7 @@ operations:
- type
- phase-offset-monitor
- phase-offset-avg-factor
+ - frequency-monitor
dump:
reply: *dev-attrs
@@ -563,6 +578,7 @@ operations:
- mode
- phase-offset-monitor
- phase-offset-avg-factor
+ - frequency-monitor
-
name: device-create-ntf
doc: Notification about device appearing
@@ -643,6 +659,7 @@ operations:
- esync-frequency-supported
- esync-pulse
- reference-sync
+ - measured-frequency
dump:
request:
diff --git a/drivers/dpll/dpll_nl.c b/drivers/dpll/dpll_nl.c
index a2b22d4921142..1e652340a5d73 100644
--- a/drivers/dpll/dpll_nl.c
+++ b/drivers/dpll/dpll_nl.c
@@ -43,11 +43,12 @@ static const struct nla_policy dpll_device_get_nl_policy[DPLL_A_ID + 1] = {
};
/* DPLL_CMD_DEVICE_SET - do */
-static const struct nla_policy dpll_device_set_nl_policy[DPLL_A_PHASE_OFFSET_AVG_FACTOR + 1] = {
+static const struct nla_policy dpll_device_set_nl_policy[DPLL_A_FREQUENCY_MONITOR + 1] = {
[DPLL_A_ID] = { .type = NLA_U32, },
[DPLL_A_MODE] = NLA_POLICY_RANGE(NLA_U32, 1, 2),
[DPLL_A_PHASE_OFFSET_MONITOR] = NLA_POLICY_MAX(NLA_U32, 1),
[DPLL_A_PHASE_OFFSET_AVG_FACTOR] = { .type = NLA_U32, },
+ [DPLL_A_FREQUENCY_MONITOR] = NLA_POLICY_MAX(NLA_U32, 1),
};
/* DPLL_CMD_PIN_ID_GET - do */
@@ -115,7 +116,7 @@ static const struct genl_split_ops dpll_nl_ops[] = {
.doit = dpll_nl_device_set_doit,
.post_doit = dpll_post_doit,
.policy = dpll_device_set_nl_policy,
- .maxattr = DPLL_A_PHASE_OFFSET_AVG_FACTOR,
+ .maxattr = DPLL_A_FREQUENCY_MONITOR,
.flags = GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
},
{
diff --git a/include/uapi/linux/dpll.h b/include/uapi/linux/dpll.h
index de0005f28e5c5..2e75d547716ea 100644
--- a/include/uapi/linux/dpll.h
+++ b/include/uapi/linux/dpll.h
@@ -218,6 +218,7 @@ enum dpll_a {
DPLL_A_CLOCK_QUALITY_LEVEL,
DPLL_A_PHASE_OFFSET_MONITOR,
DPLL_A_PHASE_OFFSET_AVG_FACTOR,
+ DPLL_A_FREQUENCY_MONITOR,
__DPLL_A_MAX,
DPLL_A_MAX = (__DPLL_A_MAX - 1)
@@ -254,6 +255,7 @@ enum dpll_a_pin {
DPLL_A_PIN_REFERENCE_SYNC,
DPLL_A_PIN_PHASE_ADJUST_GRAN,
DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET_PPT,
+ DPLL_A_PIN_MEASURED_FREQUENCY,
__DPLL_A_PIN_MAX,
DPLL_A_PIN_MAX = (__DPLL_A_PIN_MAX - 1)
--
2.52.0On Mon, 30 Mar 2026 12:55:03 +0200 Ivan Vecera wrote: > Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over > the frequency monitor feature. The attribute uses the existing > dpll_feature_state enum (enable/disable) and is present in both > device-get reply and device-set request. > > Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured > input frequency in Hz. The attribute is present in the pin-get reply. > + - > + name: frequency-monitor > + type: u32 > + enum: feature-state > + doc: Receive or request state of frequency monitor feature. reads a bit clunkily - how about: Current or desired state of the frequency monitor feature. ? > + If enabled, dpll device shall measure all currently available > + inputs for their actual input frequency. > - > name: pin > enum-name: dpll_a_pin > @@ -456,6 +463,13 @@ attribute-sets: > Value is in PPT (parts per trillion, 10^-12). > Note: This attribute provides higher resolution than the standard > fractional-frequency-offset (which is in PPM). > + - > + name: measured-frequency > + type: u64 > + doc: | > + The measured frequency of the input pin in Hz. > + This is the actual frequency being received on the pin, > + as measured by the dpll device hardware. If we make this a u64 should it be fixed point? Seems dubious that we'd ever be able to measure >4Ghz frequencies, much more likely that we'd want sub-1 precision ? So let's say this is fixed point 34.30 ?
Hi Kuba, On 4/1/26 5:05 AM, Jakub Kicinski wrote: > On Mon, 30 Mar 2026 12:55:03 +0200 Ivan Vecera wrote: >> Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over >> the frequency monitor feature. The attribute uses the existing >> dpll_feature_state enum (enable/disable) and is present in both >> device-get reply and device-set request. >> >> Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured >> input frequency in Hz. The attribute is present in the pin-get reply. > > >> + - >> + name: frequency-monitor >> + type: u32 >> + enum: feature-state >> + doc: Receive or request state of frequency monitor feature. > > reads a bit clunkily - how about: > > Current or desired state of the frequency monitor feature. > > ? Agreed, will update. > >> + If enabled, dpll device shall measure all currently available >> + inputs for their actual input frequency. >> - >> name: pin >> enum-name: dpll_a_pin >> @@ -456,6 +463,13 @@ attribute-sets: >> Value is in PPT (parts per trillion, 10^-12). >> Note: This attribute provides higher resolution than the standard >> fractional-frequency-offset (which is in PPM). >> + - >> + name: measured-frequency >> + type: u64 >> + doc: | >> + The measured frequency of the input pin in Hz. >> + This is the actual frequency being received on the pin, >> + as measured by the dpll device hardware. > > If we make this a u64 should it be fixed point? Seems dubious that we'd > ever be able to measure >4Ghz frequencies, much more likely that we'd > want sub-1 precision ? So let's say this is fixed point 34.30 ? > Good point. I'm going with a decimal divider (1000) instead of 34.30, following the same approach as DPLL_PHASE_OFFSET_DIVIDER. The value is now in millihertz (mHz) with a DPLL_PIN_MEASURED_FREQUENCY_DIVIDER constant for userspace to extract integer and fractional parts. Thanks, Ivan
On 30/03/2026 11:55, Ivan Vecera wrote: > Add DPLL_A_FREQUENCY_MONITOR device attribute to allow control over > the frequency monitor feature. The attribute uses the existing > dpll_feature_state enum (enable/disable) and is present in both > device-get reply and device-set request. > > Add DPLL_A_PIN_MEASURED_FREQUENCY pin attribute to expose the measured > input frequency in Hz. The attribute is present in the pin-get reply. > > Signed-off-by: Ivan Vecera <ivecera@redhat.com> Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
© 2016 - 2026 Red Hat, Inc.