Re: [PATCH net-next v11 13/14] dpll: zl3073x: Add support to get/set frequency on input pins

+/**
+ * zl3073x_dpll_input_ref_frequency_get - get input reference frequency
+ * @zldpll: pointer to zl3073x_dpll
+ * @ref_id: reference id
+ * @frequency: pointer to variable to store frequency
+ *
+ * Reads frequency of given input reference.
+ *
+ * Return: 0 on success, <0 on error
+ */
+static int
+zl3073x_dpll_input_ref_frequency_get(struct zl3073x_dpll *zldpll, u8 ref_id,
+				     u32 *frequency)
+{
+	struct zl3073x_dev *zldev = zldpll->dev;
+	u16 base, mult, num, denom;
+	int rc;
+
+	guard(mutex)(&zldev->multiop_lock);
+
+	/* Read reference configuration */
+	rc = zl3073x_mb_op(zldev, ZL_REG_REF_MB_SEM, ZL_REF_MB_SEM_RD,
+			   ZL_REG_REF_MB_MASK, BIT(ref_id));
+	if (rc)
+		return rc;
+
+	/* Read registers to compute resulting frequency */
+	rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_BASE, &base);
+	if (rc)
+		return rc;
+	rc = zl3073x_read_u16(zldev, ZL_REG_REF_FREQ_MULT, &mult);
+	if (rc)
+		return rc;
+	rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_M, &num);
+	if (rc)
+		return rc;
+	rc = zl3073x_read_u16(zldev, ZL_REG_REF_RATIO_N, &denom);
+	if (rc)
+		return rc;
+
+	/* Sanity check that HW has not returned zero denominator */
+	if (!denom) {
+		dev_err(zldev->dev,
+			"Zero divisor for ref %u frequency got from device\n",
+			ref_id);
+		return -EINVAL;
+	}
+
+	/* Compute the frequency */
+	*frequency = base * mult * num / denom;