Linux-RTC Archive on lore.kernel.org
 help / color / Atom feed
* [PATCH] rtc: abx80x: Add support for autocalibration filter capacitor
@ 2020-05-30 12:32 Kevin P. Fleming
  2020-05-30 12:50 ` Kevin P. Fleming
  2020-06-09 22:14 ` Rob Herring
  0 siblings, 2 replies; 7+ messages in thread
From: Kevin P. Fleming @ 2020-05-30 12:32 UTC (permalink / raw)
  To: linux-rtc, devicetree
  Cc: Kevin P. Fleming, Alessandro Zummo, Alexandre Belloni, Rob Herring

All of the parts supported by this driver can make use of a
small capacitor to improve the accuracy of the autocalibration
process for their RC oscillators. If a capacitor is connected,
a configuration register must be set to enable its use, so a
new Device Tree property has been added for that purpose.

Signed-off-by: Kevin P. Fleming <kevin+linux@km6g.us>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Rob Herring <robh+dt@kernel.org>
To: linux-rtc@vger.kernel.org
To: devicetree@vger.kernel.org
---
 .../bindings/rtc/abracon,abx80x.txt           |  6 ++++
 drivers/rtc/rtc-abx80x.c                      | 34 +++++++++++++++++++
 2 files changed, 40 insertions(+)

diff --git a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
index 2405e35a1bc0..ad5d59ed6f24 100644
--- a/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
+++ b/Documentation/devicetree/bindings/rtc/abracon,abx80x.txt
@@ -29,3 +29,9 @@ and valid to enable charging:
  - "abracon,tc-diode": should be "standard" (0.6V) or "schottky" (0.3V)
  - "abracon,tc-resistor": should be <0>, <3>, <6> or <11>. 0 disables the output
                           resistor, the other values are in kOhm.
+
+All of the devices can have a 47pf capacitor attached to increase the
+autocalibration accuracy of their RC oscillators. To enable usage of the
+capacitor the following property has to be defined:
+
+ - "abracon,autocal-filter"
diff --git a/drivers/rtc/rtc-abx80x.c b/drivers/rtc/rtc-abx80x.c
index 3521d8e8dc38..be5a814e8c0b 100644
--- a/drivers/rtc/rtc-abx80x.c
+++ b/drivers/rtc/rtc-abx80x.c
@@ -76,6 +76,9 @@
 #define ABX8XX_CFG_KEY_OSC	0xa1
 #define ABX8XX_CFG_KEY_MISC	0x9d
 
+#define ABX8XX_REG_AFCTRL	0x26
+#define ABX8XX_AUTOCAL_FILTER_ENABLE	0xa0
+
 #define ABX8XX_REG_ID0		0x28
 
 #define ABX8XX_REG_OUT_CTRL	0x30
@@ -130,6 +133,31 @@ static int abx80x_is_rc_mode(struct i2c_client *client)
 	return (flags & ABX8XX_OSS_OMODE) ? 1 : 0;
 }
 
+static int abx80x_enable_autocal_filter(struct i2c_client *client)
+{
+	int err;
+
+	/*
+	 * Write the configuration key register to enable access to the AFCTRL
+	 * register
+	 */
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_CFG_KEY,
+					ABX8XX_CFG_KEY_MISC);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write configuration key\n");
+		return -EIO;
+	}
+
+	err = i2c_smbus_write_byte_data(client, ABX8XX_REG_AFCTRL,
+					ABX8XX_AUTOCAL_FILTER_ENABLE);
+	if (err < 0) {
+		dev_err(&client->dev, "Unable to write autocal filter register\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static int abx80x_enable_trickle_charger(struct i2c_client *client,
 					 u8 trickle_cfg)
 {
@@ -825,6 +853,12 @@ static int abx80x_probe(struct i2c_client *client,
 			return err;
 	}
 
+	if (of_property_read_bool(np, "abracon,autocal_filter")) {
+		err = abx80x_enable_autocal_filter(client);
+		if (err)
+			return err;
+	}
+
 	if (client->irq > 0) {
 		dev_info(&client->dev, "IRQ %d supplied\n", client->irq);
 		err = devm_request_threaded_irq(&client->dev, client->irq, NULL,
-- 
2.26.2


^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, back to index

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-05-30 12:32 [PATCH] rtc: abx80x: Add support for autocalibration filter capacitor Kevin P. Fleming
2020-05-30 12:50 ` Kevin P. Fleming
2020-06-09 22:14 ` Rob Herring
2020-06-09 22:23   ` Kevin P. Fleming
2020-06-10 15:16     ` Alexandre Belloni
2020-06-12 11:48       ` Kevin P. Fleming
2020-06-12 14:23         ` Rob Herring

Linux-RTC Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-rtc/0 linux-rtc/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-rtc linux-rtc/ https://lore.kernel.org/linux-rtc \
		linux-rtc@vger.kernel.org
	public-inbox-index linux-rtc

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-rtc


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git