linux-kernel - [PATCH 1/2] rtc: pcf85363: add support for high-impedance output

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20231024-topic-pcf85363_hiz_output-v1-1-50908aff0e52@wolfvision.net>
Date:   Wed, 25 Oct 2023 18:21:54 +0200
From:   Javier Carrasco <javier.carrasco@...fvision.net>
To:     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>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org,
        Javier Carrasco <javier.carrasco@...fvision.net>
Subject: [PATCH 1/2] rtc: pcf85363: add support for high-impedance output

The pcf85363 provides a high-impedance (hi-Z) mode for its output. This
mode can be used to reduce power consumption in applications where the
RTC output is only required as a clock/interrupt source when the system
runs in low-power mode (i.e. serving as a clock source for a PMU when
the system is down). If the output is not needed, it can also be
completely disabled.

This implementation adds support for a hi-Z output and also uses simple
pm operations (suspend and resume) to switch the output mode from hi-Z
in normal operation to the required operation mode in sleep mode
(currently either clock or interrupt) if the "sleep" value for the
hiz-output was set.

In order to make use of the hi-Z output modeling via device tree,
check if the new "hiz-output" property is defined and set the hi-Z
mode accordingly.

Signed-off-by: Javier Carrasco <javier.carrasco@...fvision.net>
---
 drivers/rtc/rtc-pcf85363.c | 62 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 61 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-pcf85363.c b/drivers/rtc/rtc-pcf85363.c
index 540042b9eec8..82eaf8de8b33 100644
--- a/drivers/rtc/rtc-pcf85363.c
+++ b/drivers/rtc/rtc-pcf85363.c
@@ -110,9 +110,17 @@
 
 #define NVRAM_SIZE	0x40
 
+enum pcf85363_hiz_output_t {
+	PCF85363_HIZ_OFF,
+	PCF85363_HIZ_ON,
+	PCF85363_HIZ_SLEEP,
+};
+
 struct pcf85363 {
 	struct rtc_device	*rtc;
 	struct regmap		*regmap;
+
+	enum pcf85363_hiz_output_t hiz_output;
 };
 
 struct pcf85x63_config {
@@ -403,6 +411,7 @@ static int pcf85363_probe(struct i2c_client *client)
 	};
 	int ret, i, err;
 	bool wakeup_source;
+	const char *hiz_output = NULL;
 
 	if (data)
 		config = data;
@@ -433,9 +442,32 @@ static int pcf85363_probe(struct i2c_client *client)
 	pcf85363->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	pcf85363->rtc->range_max = RTC_TIMESTAMP_END_2099;
 
+	if (device_property_present(&client->dev, "hiz-output")) {
+		ret = device_property_read_string(&client->dev, "hiz-output",
+						  &hiz_output);
+		if (ret)
+			return ret;
+
+		if (!strcmp(hiz_output, "enabled")) {
+			pcf85363->hiz_output = PCF85363_HIZ_ON;
+		} else if (!strcmp(hiz_output, "sleep")) {
+			pcf85363->hiz_output = PCF85363_HIZ_SLEEP;
+		} else if (!strcmp(hiz_output, "disabled")) {
+			pcf85363->hiz_output = PCF85363_HIZ_OFF;
+		} else {
+			dev_warn(&client->dev, "Unknown hiz-output: %s. Assuming disabled",
+				 hiz_output);
+			pcf85363->hiz_output = PCF85363_HIZ_OFF;
+		}
+	} else {
+		pcf85363->hiz_output = PCF85363_HIZ_OFF;
+	}
 	wakeup_source = device_property_read_bool(&client->dev,
 						  "wakeup-source");
-	if (client->irq > 0 || wakeup_source) {
+	if (pcf85363->hiz_output != PCF85363_HIZ_OFF) {
+		regmap_update_bits(pcf85363->regmap, CTRL_PIN_IO,
+				   PIN_IO_INTAPM, PIN_IO_INTA_HIZ);
+	} else if (client->irq > 0 || wakeup_source) {
 		regmap_write(pcf85363->regmap, CTRL_FLAGS, 0);
 		regmap_update_bits(pcf85363->regmap, CTRL_PIN_IO,
 				   PIN_IO_INTAPM, PIN_IO_INTA_OUT);
@@ -474,6 +506,31 @@ static int pcf85363_probe(struct i2c_client *client)
 	return ret;
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int pcf85363_suspend(struct device *dev)
+{
+	struct pcf85363 *pcf85363 = dev_get_drvdata(dev);
+
+	if (pcf85363->hiz_output == PCF85363_HIZ_SLEEP)
+		regmap_update_bits(pcf85363->regmap, CTRL_PIN_IO, PIN_IO_INTAPM,
+				   device_may_wakeup(dev) ?  PIN_IO_INTA_OUT :
+				   PIN_IO_INTA_CLK);
+
+	return 0;
+}
+
+static int pcf85363_resume(struct device *dev)
+{
+	struct pcf85363 *pcf85363 = dev_get_drvdata(dev);
+
+	if (pcf85363->hiz_output == PCF85363_HIZ_SLEEP)
+		regmap_update_bits(pcf85363->regmap, CTRL_PIN_IO,
+				   PIN_IO_INTAPM, PIN_IO_INTA_HIZ);
+
+	return 0;
+}
+#endif
+
 static const __maybe_unused struct of_device_id dev_ids[] = {
 	{ .compatible = "nxp,pcf85263", .data = &pcf_85263_config },
 	{ .compatible = "nxp,pcf85363", .data = &pcf_85363_config },
@@ -481,9 +538,12 @@ static const __maybe_unused struct of_device_id dev_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, dev_ids);
 
+static SIMPLE_DEV_PM_OPS(pcf85363_pm_ops, pcf85363_suspend, pcf85363_resume);
+
 static struct i2c_driver pcf85363_driver = {
 	.driver	= {
 		.name	= "pcf85363",
+		.pm	= &pcf85363_pm_ops,
 		.of_match_table = of_match_ptr(dev_ids),
 	},
 	.probe = pcf85363_probe,

-- 
2.39.2