[PATCH 1/3] input: misc: pm8941-pwrkey: add software key press debouncing support

[Anjelique Melendez]

From: David Collins <collinsd@xxxxxxxxxxxxxx>

On certain PMICs, an unexpected assertion of KPDPWR_DEB (the
positive logic hardware debounced power key signal) may be seen
during the falling edge of KPDPWR_N (i.e. a power key press) when
it occurs close to the rising edge of SLEEP_CLK.  This then
triggers a spurious KPDPWR interrupt.

Handle this issue by adding software debouncing support to ignore
key events that occur within the hardware debounce delay after the
most recent key release event.

Change-Id: Ifa3809935c01aab9078ba2302397bc9ebf390021
Signed-off-by: David Collins <collinsd@xxxxxxxxxxxxxx>
Signed-off-by: Anjelique Melendez <quic_amelende@xxxxxxxxxxx>
---
 drivers/input/misc/pm8941-pwrkey.c | 115 ++++++++++++++++++++++++++---
 1 file changed, 105 insertions(+), 10 deletions(-)

diff --git a/drivers/input/misc/pm8941-pwrkey.c b/drivers/input/misc/pm8941-pwrkey.c
index 33609603245d..b912ce00ce1c 100644
--- a/drivers/input/misc/pm8941-pwrkey.c
+++ b/drivers/input/misc/pm8941-pwrkey.c
@@ -9,9 +9,11 @@
 #include <linux/input.h>
 #include <linux/interrupt.h>
 #include <linux/kernel.h>
+#include <linux/ktime.h>
 #include <linux/log2.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/reboot.h>
@@ -19,6 +21,16 @@
 
 #define PON_REV2			0x01
 
+#define PON_SUBTYPE			0x05
+
+#define PON_SUBTYPE_PRIMARY		0x01
+#define PON_SUBTYPE_SECONDARY		0x02
+#define PON_SUBTYPE_1REG		0x03
+#define PON_SUBTYPE_GEN2_PRIMARY	0x04
+#define PON_SUBTYPE_GEN2_SECONDARY	0x05
+#define PON_SUBTYPE_GEN3_PBS		0x08
+#define PON_SUBTYPE_GEN3_HLOS		0x09
+
 #define PON_RT_STS			0x10
 #define  PON_KPDPWR_N_SET		BIT(0)
 #define  PON_RESIN_N_SET		BIT(1)
@@ -44,6 +56,8 @@ struct pm8941_data {
 	unsigned int	status_bit;
 	bool		supports_ps_hold_poff_config;
 	bool		supports_debounce_config;
+	bool		needs_sw_debounce;
+	bool		has_pon_pbs;
 	const char	*name;
 	const char	*phys;
 };
@@ -52,13 +66,17 @@ struct pm8941_pwrkey {
 	struct device *dev;
 	int irq;
 	u32 baseaddr;
+	u32 pon_pbs_baseaddr;
 	struct regmap *regmap;
 	struct input_dev *input;
 
 	unsigned int revision;
+	unsigned int subtype;
 	struct notifier_block reboot_notifier;
 
 	u32 code;
+	u32 sw_debounce_time_us;
+	ktime_t last_release_time;
 	const struct pm8941_data *data;
 };
 
@@ -126,19 +144,65 @@ static irqreturn_t pm8941_pwrkey_irq(int irq, void *_data)
 	struct pm8941_pwrkey *pwrkey = _data;
 	unsigned int sts;
 	int error;
+	u64 elapsed_us;
+
+	if (pwrkey->sw_debounce_time_us) {
+		elapsed_us = ktime_us_delta(ktime_get(),
+					    pwrkey->last_release_time);
+		if (elapsed_us < pwrkey->sw_debounce_time_us) {
+			dev_dbg(pwrkey->dev, "ignoring key event received after %llu us, debounce time=%u us\n",
+				elapsed_us, pwrkey->sw_debounce_time_us);
+			return IRQ_HANDLED;
+		}
+	}
 
 	error = regmap_read(pwrkey->regmap,
 			    pwrkey->baseaddr + PON_RT_STS, &sts);
 	if (error)
 		return IRQ_HANDLED;
 
-	input_report_key(pwrkey->input, pwrkey->code,
-			 sts & pwrkey->data->status_bit);
+	sts &= pwrkey->data->status_bit;
+
+	if (pwrkey->sw_debounce_time_us && !sts)
+		pwrkey->last_release_time = ktime_get();
+
+	input_report_key(pwrkey->input, pwrkey->code, sts);
 	input_sync(pwrkey->input);
 
 	return IRQ_HANDLED;
 }
 
+static int pm8941_pwrkey_sw_debounce_init(struct pm8941_pwrkey *pwrkey)
+{
+	unsigned int val, addr;
+	int error;
+
+	if (pwrkey->data->has_pon_pbs && !pwrkey->pon_pbs_baseaddr) {
+		dev_err(pwrkey->dev, "PON_PBS address missing, can't read HW debounce time\n");
+		return 0;
+	}
+
+	if (pwrkey->pon_pbs_baseaddr)
+		addr = pwrkey->pon_pbs_baseaddr + PON_DBC_CTL;
+	else
+		addr = pwrkey->baseaddr + PON_DBC_CTL;
+	error = regmap_read(pwrkey->regmap, addr, &val);
+	if (error)
+		return error;
+
+	if (pwrkey->subtype >= PON_SUBTYPE_GEN2_PRIMARY)
+		pwrkey->sw_debounce_time_us = 2 * USEC_PER_SEC /
+						(1 << (0xf - (val & 0xf)));
+	else
+		pwrkey->sw_debounce_time_us = 2 * USEC_PER_SEC /
+						(1 << (0x7 - (val & 0x7)));
+
+	dev_dbg(pwrkey->dev, "SW debounce time = %u us\n",
+		pwrkey->sw_debounce_time_us);
+
+	return 0;
+}
+
 static int __maybe_unused pm8941_pwrkey_suspend(struct device *dev)
 {
 	struct pm8941_pwrkey *pwrkey = dev_get_drvdata(dev);
@@ -167,6 +231,8 @@ static int pm8941_pwrkey_probe(struct platform_device *pdev)
 	struct pm8941_pwrkey *pwrkey;
 	bool pull_up;
 	struct device *parent;
+	struct device_node *regmap_node;
+	const __be32 *addr;
 	u32 req_delay;
 	int error;
 
@@ -188,8 +254,10 @@ static int pm8941_pwrkey_probe(struct platform_device *pdev)
 	pwrkey->data = of_device_get_match_data(&pdev->dev);
 
 	parent = pdev->dev.parent;
+	regmap_node = pdev->dev.of_node;
 	pwrkey->regmap = dev_get_regmap(parent, NULL);
 	if (!pwrkey->regmap) {
+		regmap_node = parent->of_node;
 		/*
 		 * We failed to get regmap for parent. Let's see if we are
 		 * a child of pon node and read regmap and reg from its
@@ -200,15 +268,21 @@ static int pm8941_pwrkey_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "failed to locate regmap\n");
 			return -ENODEV;
 		}
+	}
 
-		error = of_property_read_u32(parent->of_node,
-					     "reg", &pwrkey->baseaddr);
-	} else {
-		error = of_property_read_u32(pdev->dev.of_node, "reg",
-					     &pwrkey->baseaddr);
+	addr = of_get_address(regmap_node, 0, NULL, NULL);
+	if (!addr) {
+		dev_err(&pdev->dev, "reg property missing\n");
+		return -EINVAL;
+	}
+	pwrkey->baseaddr = be32_to_cpu(*addr);
+
+	if (pwrkey->data->has_pon_pbs) {
+		/* PON_PBS base address is optional */
+		addr = of_get_address(regmap_node, 1, NULL, NULL);
+		if (addr)
+			pwrkey->pon_pbs_baseaddr = be32_to_cpu(*addr);
 	}
-	if (error)
-		return error;
 
 	pwrkey->irq = platform_get_irq(pdev, 0);
 	if (pwrkey->irq < 0)
@@ -217,7 +291,14 @@ static int pm8941_pwrkey_probe(struct platform_device *pdev)
 	error = regmap_read(pwrkey->regmap, pwrkey->baseaddr + PON_REV2,
 			    &pwrkey->revision);
 	if (error) {
-		dev_err(&pdev->dev, "failed to set debounce: %d\n", error);
+		dev_err(&pdev->dev, "failed to read revision: %d\n", error);
+		return error;
+	}
+
+	error = regmap_read(pwrkey->regmap, pwrkey->baseaddr + PON_SUBTYPE,
+			    &pwrkey->subtype);
+	if (error) {
+		dev_err(&pdev->dev, "failed to read subtype: %d\n", error);
 		return error;
 	}
 
@@ -255,6 +336,12 @@ static int pm8941_pwrkey_probe(struct platform_device *pdev)
 		}
 	}
 
+	if (pwrkey->data->needs_sw_debounce) {
+		error = pm8941_pwrkey_sw_debounce_init(pwrkey);
+		if (error)
+			return error;
+	}
+
 	if (pwrkey->data->pull_up_bit) {
 		error = regmap_update_bits(pwrkey->regmap,
 					   pwrkey->baseaddr + PON_PULL_CTL,
@@ -316,6 +403,8 @@ static const struct pm8941_data pwrkey_data = {
 	.phys = "pm8941_pwrkey/input0",
 	.supports_ps_hold_poff_config = true,
 	.supports_debounce_config = true,
+	.needs_sw_debounce = true,
+	.has_pon_pbs = false,
 };
 
 static const struct pm8941_data resin_data = {
@@ -325,6 +414,8 @@ static const struct pm8941_data resin_data = {
 	.phys = "pm8941_resin/input0",
 	.supports_ps_hold_poff_config = true,
 	.supports_debounce_config = true,
+	.needs_sw_debounce = true,
+	.has_pon_pbs = false,
 };
 
 static const struct pm8941_data pon_gen3_pwrkey_data = {
@@ -333,6 +424,8 @@ static const struct pm8941_data pon_gen3_pwrkey_data = {
 	.phys = "pmic_pwrkey/input0",
 	.supports_ps_hold_poff_config = false,
 	.supports_debounce_config = false,
+	.needs_sw_debounce = true,
+	.has_pon_pbs = true,
 };
 
 static const struct pm8941_data pon_gen3_resin_data = {
@@ -341,6 +434,8 @@ static const struct pm8941_data pon_gen3_resin_data = {
 	.phys = "pmic_resin/input0",
 	.supports_ps_hold_poff_config = false,
 	.supports_debounce_config = false,
+	.needs_sw_debounce = true,
+	.has_pon_pbs = true,
 };
 
 static const struct of_device_id pm8941_pwr_key_id_table[] = {
-- 
2.34.1