dpll: expose fractional frequency offset value to user

Add a new netlink attribute to expose fractional frequency offset value
for a pin. Add an op to get the value from the driver.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Acked-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Acked-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@intel.com>
Link: https://lore.kernel.org/r/20240103132838.1501801-2-jiri@resnulli.us
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/dpll.yaml

@@ -296,6 +296,16 @@ attribute-sets:
       -
         name: phase-offset
         type: s64
+      -
+        name: fractional-frequency-offset
+        type: sint
+        doc: |
+          The FFO (Fractional Frequency Offset) between the RX and TX
+          symbol rate on the media associated with the pin:
+          (rx_frequency-tx_frequency)/rx_frequency
+          Value is in PPM (parts per million).
+          This may be implemented for example for pin of type
+          PIN_TYPE_SYNCE_ETH_PORT.
   -
     name: pin-parent-device
     subset-of: pin
@@ -460,6 +470,7 @@ operations:
             - phase-adjust-min
             - phase-adjust-max
             - phase-adjust
+            - fractional-frequency-offset
 
       dump:
         pre: dpll-lock-dumpit

drivers/dpll/dpll_netlink.c

@@ -263,6 +263,27 @@ dpll_msg_add_phase_offset(struct sk_buff *msg, struct dpll_pin *pin,
 	return 0;
 }
 
+static int dpll_msg_add_ffo(struct sk_buff *msg, struct dpll_pin *pin,
+			    struct dpll_pin_ref *ref,
+			    struct netlink_ext_ack *extack)
+{
+	const struct dpll_pin_ops *ops = dpll_pin_ops(ref);
+	struct dpll_device *dpll = ref->dpll;
+	s64 ffo;
+	int ret;
+
+	if (!ops->ffo_get)
+		return 0;
+	ret = ops->ffo_get(pin, dpll_pin_on_dpll_priv(dpll, pin),
+			   dpll, dpll_priv(dpll), &ffo, extack);
+	if (ret) {
+		if (ret == -ENODATA)
+			return 0;
+		return ret;
+	}
+	return nla_put_sint(msg, DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET, ffo);
+}
+
 static int
 dpll_msg_add_pin_freq(struct sk_buff *msg, struct dpll_pin *pin,
 		      struct dpll_pin_ref *ref, struct netlink_ext_ack *extack)
@@ -440,6 +461,9 @@ dpll_cmd_pin_get_one(struct sk_buff *msg, struct dpll_pin *pin,
 			prop->phase_range.max))
 		return -EMSGSIZE;
 	ret = dpll_msg_add_pin_phase_adjust(msg, pin, ref, extack);
+	if (ret)
+		return ret;
+	ret = dpll_msg_add_ffo(msg, pin, ref, extack);
 	if (ret)
 		return ret;
 	if (xa_empty(&pin->parent_refs))

include/linux/dpll.h

@@ -77,6 +77,9 @@ struct dpll_pin_ops {
 				const struct dpll_device *dpll, void *dpll_priv,
 				const s32 phase_adjust,
 				struct netlink_ext_ack *extack);
+	int (*ffo_get)(const struct dpll_pin *pin, void *pin_priv,
+		       const struct dpll_device *dpll, void *dpll_priv,
+		       s64 *ffo, struct netlink_ext_ack *extack);
 };
 
 struct dpll_pin_frequency {

include/uapi/linux/dpll.h

@@ -179,6 +179,7 @@ enum dpll_a_pin {
 	DPLL_A_PIN_PHASE_ADJUST_MAX,
 	DPLL_A_PIN_PHASE_ADJUST,
 	DPLL_A_PIN_PHASE_OFFSET,
+	DPLL_A_PIN_FRACTIONAL_FREQUENCY_OFFSET,
 
 	__DPLL_A_PIN_MAX,
 	DPLL_A_PIN_MAX = (__DPLL_A_PIN_MAX - 1)