clk: si570: Skip NVM to RAM recall operation if an optional property is set

Recalling NVM data into RAM during probe() initiates a re-calibration of
the clock. If the clock is already in-use, the recall operation can cause
a glitch on the frequency out. At power on, the factory data are loaded
from NVM into RAM by default. If the clock frequency has been changed
since power on, the recall operation can be used to re-initialize the clock
to factory setting.

Signed-off-by: Michal Simek <[email protected]>
Signed-off-by: Saeed Nowshadi <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Stephen Boyd <[email protected]>

Author: saeedn-xilinx

drivers/clk/clk-si570.c

@@ -4,7 +4,7 @@
  *
  * Copyright (C) 2010, 2011 Ericsson AB.
  * Copyright (C) 2011 Guenter Roeck.
- * Copyright (C) 2011 - 2013 Xilinx Inc.
+ * Copyright (C) 2011 - 2021 Xilinx Inc.
  *
  * Author: Guenter Roeck <[email protected]>
  *	   Sören Brinkmann <[email protected]>
@@ -123,14 +123,18 @@ static int si570_get_divs(struct clk_si570 *data, u64 *rfreq,
  * si570_get_defaults() - Get default values
  * @data:	Driver data structure
  * @fout:	Factory frequency output
+ * @skip_recall:	If true, don't recall NVM into RAM
  * Returns 0 on success, negative errno otherwise.
  */
-static int si570_get_defaults(struct clk_si570 *data, u64 fout)
+static int si570_get_defaults(struct clk_si570 *data, u64 fout,
+			      bool skip_recall)
 {
 	int err;
 	u64 fdco;
 
-	regmap_write(data->regmap, SI570_REG_CONTROL, SI570_CNTRL_RECALL);
+	if (!skip_recall)
+		regmap_write(data->regmap, SI570_REG_CONTROL,
+			     SI570_CNTRL_RECALL);
 
 	err = si570_get_divs(data, &data->rfreq, &data->n1, &data->hs_div);
 	if (err)
@@ -400,6 +404,7 @@ static int si570_probe(struct i2c_client *client,
 	struct clk_si570 *data;
 	struct clk_init_data init;
 	u32 initial_fout, factory_fout, stability;
+	bool skip_recall;
 	int err;
 	enum clk_si570_variant variant = id->driver_data;
 
@@ -441,14 +446,17 @@ static int si570_probe(struct i2c_client *client,
 		return err;
 	}
 
+	skip_recall = of_property_read_bool(client->dev.of_node,
+					    "silabs,skip-recall");
+
 	data->regmap = devm_regmap_init_i2c(client, &si570_regmap_config);
 	if (IS_ERR(data->regmap)) {
 		dev_err(&client->dev, "failed to allocate register map\n");
 		return PTR_ERR(data->regmap);
 	}
 
 	i2c_set_clientdata(client, data);
-	err = si570_get_defaults(data, factory_fout);
+	err = si570_get_defaults(data, factory_fout, skip_recall);
 	if (err)
 		return err;