i2c: core: Allow override timing properties with 0

Some drivers may allow to override properties with 0 value when defaults
are not in use, thus, replace memset() with corresponding per property
update.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/busses/i2c-rcar.c

@@ -920,7 +920,7 @@ static int rcar_i2c_probe(struct platform_device *pdev)
 	struct rcar_i2c_priv *priv;
 	struct i2c_adapter *adap;
 	struct device *dev = &pdev->dev;
-	struct i2c_timings i2c_t;
+	struct i2c_timings i2c_t = { 0 };
 	int ret;
 
 	/* Otherwise logic will break because some bytes must always use PIO */

drivers/i2c/i2c-core-base.c

@@ -1593,23 +1593,21 @@ EXPORT_SYMBOL(i2c_del_adapter);
  * @dev: The device to scan for I2C timing properties
  * @t: the i2c_timings struct to be filled with values
  * @use_defaults: bool to use sane defaults derived from the I2C specification
- *		  when properties are not found, otherwise use 0
+ *		  when properties are not found, otherwise don't update
  *
  * Scan the device for the generic I2C properties describing timing parameters
  * for the signal and fill the given struct with the results. If a property was
  * not found and use_defaults was true, then maximum timings are assumed which
  * are derived from the I2C specification. If use_defaults is not used, the
- * results will be 0, so drivers can apply their own defaults later. The latter
- * is mainly intended for avoiding regressions of existing drivers which want
- * to switch to this function. New drivers almost always should use the defaults.
+ * results will be as before, so drivers can apply their own defaults before
+ * calling this helper. The latter is mainly intended for avoiding regressions
+ * of existing drivers which want to switch to this function. New drivers
+ * almost always should use the defaults.
  */
-
 void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults)
 {
 	int ret;
 
-	memset(t, 0, sizeof(*t));
-
 	ret = device_property_read_u32(dev, "clock-frequency", &t->bus_freq_hz);
 	if (ret && use_defaults)
 		t->bus_freq_hz = I2C_MAX_STANDARD_MODE_FREQ;
@@ -1632,19 +1630,25 @@ void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_de
 			t->scl_fall_ns = 120;
 	}
 
-	device_property_read_u32(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns);
+	ret = device_property_read_u32(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns);
+	if (ret && use_defaults)
+		t->scl_int_delay_ns = 0;
 
 	ret = device_property_read_u32(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns);
 	if (ret && use_defaults)
 		t->sda_fall_ns = t->scl_fall_ns;
 
-	device_property_read_u32(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns);
+	ret = device_property_read_u32(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns);
+	if (ret && use_defaults)
+		t->sda_hold_ns = 0;
 
-	device_property_read_u32(dev, "i2c-digital-filter-width-ns",
-				 &t->digital_filter_width_ns);
+	ret = device_property_read_u32(dev, "i2c-digital-filter-width-ns", &t->digital_filter_width_ns);
+	if (ret && use_defaults)
+		t->digital_filter_width_ns = 0;
 
-	device_property_read_u32(dev, "i2c-analog-filter-cutoff-frequency",
-				 &t->analog_filter_cutoff_freq_hz);
+	ret = device_property_read_u32(dev, "i2c-analog-filter-cutoff-frequency", &t->analog_filter_cutoff_freq_hz);
+	if (ret && use_defaults)
+		t->analog_filter_cutoff_freq_hz = 0;
 }
 EXPORT_SYMBOL_GPL(i2c_parse_fw_timings);