dpll: zl3073x: Fetch invariants during probe

Several configuration parameters will remain constant at runtime,
so we can load them during probe to avoid excessive reads from
the hardware.

Read the following parameters from the device during probe and store
them for later use:

* enablement status and frequencies of the synthesizers and their
  associated DPLL channels
* enablement status and type (single-ended or differential) of input pins
* associated synthesizers, signal format, and enablement status of
  outputs

Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://patch.msgid.link/20250704182202.1641943-7-ivecera@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: ivecera

drivers/dpll/zl3073x/core.c

@@ -6,10 +6,12 @@
 #include <linux/dev_printk.h>
 #include <linux/device.h>
 #include <linux/export.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/netlink.h>
 #include <linux/regmap.h>
 #include <linux/sprintf.h>
+#include <linux/string_choices.h>
 #include <linux/unaligned.h>
 #include <net/devlink.h>
 
@@ -383,6 +385,248 @@ int zl3073x_poll_zero_u8(struct zl3073x_dev *zldev, unsigned int reg, u8 mask)
 					ZL_POLL_SLEEP_US, ZL_POLL_TIMEOUT_US);
 }
 
+int zl3073x_mb_op(struct zl3073x_dev *zldev, unsigned int op_reg, u8 op_val,
+		  unsigned int mask_reg, u16 mask_val)
+{
+	int rc;
+
+	/* Set mask for the operation */
+	rc = zl3073x_write_u16(zldev, mask_reg, mask_val);
+	if (rc)
+		return rc;
+
+	/* Trigger the operation */
+	rc = zl3073x_write_u8(zldev, op_reg, op_val);
+	if (rc)
+		return rc;
+
+	/* Wait for the operation to actually finish */
+	return zl3073x_poll_zero_u8(zldev, op_reg, op_val);
+}
+
+/**
+ * zl3073x_ref_state_fetch - get input reference state
+ * @zldev: pointer to zl3073x_dev structure
+ * @index: input reference index to fetch state for
+ *
+ * Function fetches information for the given input reference that are
+ * invariant and stores them for later use.
+ *
+ * Return: 0 on success, <0 on error
+ */
+static int
+zl3073x_ref_state_fetch(struct zl3073x_dev *zldev, u8 index)
+{
+	struct zl3073x_ref *input = &zldev->ref[index];
+	u8 ref_config;
+	int rc;
+
+	/* If the input is differential then the configuration for N-pin
+	 * reference is ignored and P-pin config is used for both.
+	 */
+	if (zl3073x_is_n_pin(index) &&
+	    zl3073x_ref_is_diff(zldev, index - 1)) {
+		input->enabled = zl3073x_ref_is_enabled(zldev, index - 1);
+		input->diff = true;
+
+		return 0;
+	}
+
+	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(index));
+	if (rc)
+		return rc;
+
+	/* Read ref_config register */
+	rc = zl3073x_read_u8(zldev, ZL_REG_REF_CONFIG, &ref_config);
+	if (rc)
+		return rc;
+
+	input->enabled = FIELD_GET(ZL_REF_CONFIG_ENABLE, ref_config);
+	input->diff = FIELD_GET(ZL_REF_CONFIG_DIFF_EN, ref_config);
+
+	dev_dbg(zldev->dev, "REF%u is %s and configured as %s\n", index,
+		str_enabled_disabled(input->enabled),
+		input->diff ? "differential" : "single-ended");
+
+	return rc;
+}
+
+/**
+ * zl3073x_out_state_fetch - get output state
+ * @zldev: pointer to zl3073x_dev structure
+ * @index: output index to fetch state for
+ *
+ * Function fetches information for the given output (not output pin)
+ * that are invariant and stores them for later use.
+ *
+ * Return: 0 on success, <0 on error
+ */
+static int
+zl3073x_out_state_fetch(struct zl3073x_dev *zldev, u8 index)
+{
+	struct zl3073x_out *out = &zldev->out[index];
+	u8 output_ctrl, output_mode;
+	int rc;
+
+	/* Read output configuration */
+	rc = zl3073x_read_u8(zldev, ZL_REG_OUTPUT_CTRL(index), &output_ctrl);
+	if (rc)
+		return rc;
+
+	/* Store info about output enablement and synthesizer the output
+	 * is connected to.
+	 */
+	out->enabled = FIELD_GET(ZL_OUTPUT_CTRL_EN, output_ctrl);
+	out->synth = FIELD_GET(ZL_OUTPUT_CTRL_SYNTH_SEL, output_ctrl);
+
+	dev_dbg(zldev->dev, "OUT%u is %s and connected to SYNTH%u\n", index,
+		str_enabled_disabled(out->enabled), out->synth);
+
+	guard(mutex)(&zldev->multiop_lock);
+
+	/* Read output configuration */
+	rc = zl3073x_mb_op(zldev, ZL_REG_OUTPUT_MB_SEM, ZL_OUTPUT_MB_SEM_RD,
+			   ZL_REG_OUTPUT_MB_MASK, BIT(index));
+	if (rc)
+		return rc;
+
+	/* Read output_mode */
+	rc = zl3073x_read_u8(zldev, ZL_REG_OUTPUT_MODE, &output_mode);
+	if (rc)
+		return rc;
+
+	/* Extract and store output signal format */
+	out->signal_format = FIELD_GET(ZL_OUTPUT_MODE_SIGNAL_FORMAT,
+				       output_mode);
+
+	dev_dbg(zldev->dev, "OUT%u has signal format 0x%02x\n", index,
+		out->signal_format);
+
+	return rc;
+}
+
+/**
+ * zl3073x_synth_state_fetch - get synth state
+ * @zldev: pointer to zl3073x_dev structure
+ * @index: synth index to fetch state for
+ *
+ * Function fetches information for the given synthesizer that are
+ * invariant and stores them for later use.
+ *
+ * Return: 0 on success, <0 on error
+ */
+static int
+zl3073x_synth_state_fetch(struct zl3073x_dev *zldev, u8 index)
+{
+	struct zl3073x_synth *synth = &zldev->synth[index];
+	u16 base, m, n;
+	u8 synth_ctrl;
+	u32 mult;
+	int rc;
+
+	/* Read synth control register */
+	rc = zl3073x_read_u8(zldev, ZL_REG_SYNTH_CTRL(index), &synth_ctrl);
+	if (rc)
+		return rc;
+
+	/* Store info about synth enablement and DPLL channel the synth is
+	 * driven by.
+	 */
+	synth->enabled = FIELD_GET(ZL_SYNTH_CTRL_EN, synth_ctrl);
+	synth->dpll = FIELD_GET(ZL_SYNTH_CTRL_DPLL_SEL, synth_ctrl);
+
+	dev_dbg(zldev->dev, "SYNTH%u is %s and driven by DPLL%u\n", index,
+		str_enabled_disabled(synth->enabled), synth->dpll);
+
+	guard(mutex)(&zldev->multiop_lock);
+
+	/* Read synth configuration */
+	rc = zl3073x_mb_op(zldev, ZL_REG_SYNTH_MB_SEM, ZL_SYNTH_MB_SEM_RD,
+			   ZL_REG_SYNTH_MB_MASK, BIT(index));
+	if (rc)
+		return rc;
+
+	/* The output frequency is determined by the following formula:
+	 * base * multiplier * numerator / denominator
+	 *
+	 * Read registers with these values
+	 */
+	rc = zl3073x_read_u16(zldev, ZL_REG_SYNTH_FREQ_BASE, &base);
+	if (rc)
+		return rc;
+
+	rc = zl3073x_read_u32(zldev, ZL_REG_SYNTH_FREQ_MULT, &mult);
+	if (rc)
+		return rc;
+
+	rc = zl3073x_read_u16(zldev, ZL_REG_SYNTH_FREQ_M, &m);
+	if (rc)
+		return rc;
+
+	rc = zl3073x_read_u16(zldev, ZL_REG_SYNTH_FREQ_N, &n);
+	if (rc)
+		return rc;
+
+	/* Check denominator for zero to avoid div by 0 */
+	if (!n) {
+		dev_err(zldev->dev,
+			"Zero divisor for SYNTH%u retrieved from device\n",
+			index);
+		return -EINVAL;
+	}
+
+	/* Compute and store synth frequency */
+	zldev->synth[index].freq = div_u64(mul_u32_u32(base * m, mult), n);
+
+	dev_dbg(zldev->dev, "SYNTH%u frequency: %u Hz\n", index,
+		zldev->synth[index].freq);
+
+	return rc;
+}
+
+static int
+zl3073x_dev_state_fetch(struct zl3073x_dev *zldev)
+{
+	int rc;
+	u8 i;
+
+	for (i = 0; i < ZL3073X_NUM_REFS; i++) {
+		rc = zl3073x_ref_state_fetch(zldev, i);
+		if (rc) {
+			dev_err(zldev->dev,
+				"Failed to fetch input state: %pe\n",
+				ERR_PTR(rc));
+			return rc;
+		}
+	}
+
+	for (i = 0; i < ZL3073X_NUM_SYNTHS; i++) {
+		rc = zl3073x_synth_state_fetch(zldev, i);
+		if (rc) {
+			dev_err(zldev->dev,
+				"Failed to fetch synth state: %pe\n",
+				ERR_PTR(rc));
+			return rc;
+		}
+	}
+
+	for (i = 0; i < ZL3073X_NUM_OUTS; i++) {
+		rc = zl3073x_out_state_fetch(zldev, i);
+		if (rc) {
+			dev_err(zldev->dev,
+				"Failed to fetch output state: %pe\n",
+				ERR_PTR(rc));
+			return rc;
+		}
+	}
+
+	return rc;
+}
+
 /**
  * zl3073x_dev_probe - initialize zl3073x device
  * @zldev: pointer to zl3073x device
@@ -450,6 +694,11 @@ int zl3073x_dev_probe(struct zl3073x_dev *zldev,
 		return dev_err_probe(zldev->dev, rc,
 				     "Failed to initialize mutex\n");
 
+	/* Fetch device state */
+	rc = zl3073x_dev_state_fetch(zldev);
+	if (rc)
+		return rc;
+
 	/* Register the devlink instance and parameters */
 	rc = zl3073x_devlink_register(zldev);
 	if (rc)