linux-kernel - [PATCH 1/2] rtc: pcf85363: add support for the quartz-load-femtofarads property

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Date:   Mon, 13 Feb 2023 10:50:17 +0100
From:   Javier Carrasco <javier.carrasco@...fvision.net>
To:     linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
CC:     Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Michael Riesch <michael.riesch@...fvision.net>,
        Javier Carrasco <javier.carrasco@...fvision.net>
Subject: [PATCH 1/2] rtc: pcf85363: add support for the quartz-load-femtofarads property

The quartz oscillator load capacitance of the PCF85263 and PCF85363 can
be adjusted to 6 pF, 7 pF (default) and 12.5 pF with the CL[1:0] bits in
the oscillator control register (address 25h).

Signed-off-by: Javier Carrasco <javier.carrasco@...fvision.net>
---
 drivers/rtc/rtc-pcf85363.c | 37 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 36 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-pcf85363.c b/drivers/rtc/rtc-pcf85363.c
index c05b722f0060..941f9264cf0a 100644
--- a/drivers/rtc/rtc-pcf85363.c
+++ b/drivers/rtc/rtc-pcf85363.c
@@ -101,6 +101,10 @@
 #define PIN_IO_INTA_OUT	2
 #define PIN_IO_INTA_HIZ	3
 
+#define OSC_CAP_SEL	GENMASK(1, 0)
+#define OSC_CAP_6000	0x01
+#define OSC_CAP_12500	0x02
+
 #define STOP_EN_STOP	BIT(0)
 
 #define RESET_CPR	0xa4
@@ -117,6 +121,32 @@ struct pcf85x63_config {
 	unsigned int num_nvram;
 };
 
+static int pcf85363_load_capacitance(struct pcf85363 *pcf85363, struct device_node *node)
+{
+	u32 load = 7000;
+	u8 value = 0;
+
+	of_property_read_u32(node, "quartz-load-femtofarads", &load);
+
+	switch (load) {
+	default:
+		dev_warn(&pcf85363->rtc->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 7000",
+			 load);
+		fallthrough;
+	case 7000:
+		break;
+	case 6000:
+		value |= OSC_CAP_6000;
+		break;
+	case 12500:
+		value |= OSC_CAP_12500;
+		break;
+	}
+
+	return regmap_update_bits(pcf85363->regmap, CTRL_OSCILLATOR,
+				  OSC_CAP_SEL, value);
+}
+
 static int pcf85363_rtc_read_time(struct device *dev, struct rtc_time *tm)
 {
 	struct pcf85363 *pcf85363 = dev_get_drvdata(dev);
@@ -372,7 +402,7 @@ static int pcf85363_probe(struct i2c_client *client)
 			.reg_write = pcf85363_nvram_write,
 		},
 	};
-	int ret, i;
+	int ret, i, err;
 
 	if (data)
 		config = data;
@@ -394,6 +424,11 @@ static int pcf85363_probe(struct i2c_client *client)
 	if (IS_ERR(pcf85363->rtc))
 		return PTR_ERR(pcf85363->rtc);
 
+	err = pcf85363_load_capacitance(pcf85363, client->dev.of_node);
+	if (err < 0)
+		dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
+			 err);
+
 	pcf85363->rtc->ops = &rtc_ops;
 	pcf85363->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	pcf85363->rtc->range_max = RTC_TIMESTAMP_END_2099;
-- 
2.37.2


Javier Carrasco 
Research and Development

Wolfvision GmbH 
Oberes Ried 14 | 6833 Klaus | Austria 
Tel: +43 5523 52250 <tel:+43552352250> | Mail: javier.carrasco@...fvision.net <mailto:javier.carrasco@...fvision.net>

Website: wolfvision.com <www.wolfvision.com> 
Firmenbuch / Commercial Register: FN283521v Feldkirch/Austria