linux-kernel - [PATCH] Input: tsc2007 - enable GPIO chips that can sleep

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Date:   Wed, 13 Jul 2022 10:42:47 +0200
From:   Benjamin Bara <bbara93@...il.com>
To:     dmitry.torokhov@...il.com
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Bara <benjamin.bara@...data.com>,
        Richard Leitner <richard.leitner@...data.com>
Subject: [PATCH] Input: tsc2007 - enable GPIO chips that can sleep

From: Benjamin Bara <benjamin.bara@...data.com>

This enables the usage of "can_sleep" GPIO chips as "pin up" GPIO.
This might be the case if the GPIO chip is an expander behind i2c.

Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
Signed-off-by: Richard Leitner <richard.leitner@...data.com>
---
 drivers/input/touchscreen/tsc2007.h      |  1 +
 drivers/input/touchscreen/tsc2007_core.c | 38 ++++++++++++++++++++----
 2 files changed, 34 insertions(+), 5 deletions(-)

diff --git a/drivers/input/touchscreen/tsc2007.h b/drivers/input/touchscreen/tsc2007.h
index 69b08dd6c8df..29bd1ff22c72 100644
--- a/drivers/input/touchscreen/tsc2007.h
+++ b/drivers/input/touchscreen/tsc2007.h
@@ -78,6 +78,7 @@ struct tsc2007 {
 	bool			stopped;
 
 	int			(*get_pendown_state)(struct device *);
+	int			(*get_pendown_state_cansleep)(struct device *);
 	void			(*clear_penirq)(void);
 
 	struct mutex		mlock;
diff --git a/drivers/input/touchscreen/tsc2007_core.c b/drivers/input/touchscreen/tsc2007_core.c
index 3e871d182c40..0ad4c3c41297 100644
--- a/drivers/input/touchscreen/tsc2007_core.c
+++ b/drivers/input/touchscreen/tsc2007_core.c
@@ -20,6 +20,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
 #include <linux/input.h>
 #include <linux/interrupt.h>
 #include <linux/i2c.h>
@@ -108,6 +109,14 @@ bool tsc2007_is_pen_down(struct tsc2007 *ts)
 	return ts->get_pendown_state(&ts->client->dev);
 }
 
+bool tsc2007_is_pen_down_cansleep(struct tsc2007 *ts)
+{
+	if (!ts->get_pendown_state_cansleep)
+		return true;
+
+	return ts->get_pendown_state_cansleep(&ts->client->dev);
+}
+
 static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
 {
 	struct tsc2007 *ts = handle;
@@ -115,7 +124,7 @@ static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
 	struct ts_event tc;
 	u32 rt;
 
-	while (!ts->stopped && tsc2007_is_pen_down(ts)) {
+	while (!ts->stopped && tsc2007_is_pen_down_cansleep(ts)) {
 
 		/* pen is down, continue with the measurement */
 
@@ -125,7 +134,7 @@ static irqreturn_t tsc2007_soft_irq(int irq, void *handle)
 
 		rt = tsc2007_calculate_resistance(ts, &tc);
 
-		if (!rt && !ts->get_pendown_state) {
+		if (!rt && !ts->get_pendown_state_cansleep) {
 			/*
 			 * If pressure reported is 0 and we don't have
 			 * callback to check pendown state, we have to
@@ -229,6 +238,14 @@ static int tsc2007_get_pendown_state_gpio(struct device *dev)
 	return gpiod_get_value(ts->gpiod);
 }
 
+static int tsc2007_get_pendown_state_gpio_cansleep(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct tsc2007 *ts = i2c_get_clientdata(client);
+
+	return gpiod_get_value_cansleep(ts->gpiod);
+}
+
 static int tsc2007_probe_properties(struct device *dev, struct tsc2007 *ts)
 {
 	u32 val32;
@@ -264,10 +281,21 @@ static int tsc2007_probe_properties(struct device *dev, struct tsc2007 *ts)
 	if (IS_ERR(ts->gpiod))
 		return PTR_ERR(ts->gpiod);
 
-	if (ts->gpiod)
-		ts->get_pendown_state = tsc2007_get_pendown_state_gpio;
-	else
+	if (ts->gpiod) {
+		/* to support detection during the hard IRQ, the GPIO chip is required to not sleep.
+		 * this might be the case if the GPIO is e.g. behind an i2c-based GPIO expander.
+		 * it is fine to sleep later in the soft IRQ, as it is threaded.
+		 */
+		ts->get_pendown_state_cansleep = tsc2007_get_pendown_state_gpio_cansleep;
+		if (gpiod_to_chip(ts->gpiod) && !gpiod_to_chip(ts->gpiod)->can_sleep) {
+			ts->get_pendown_state = tsc2007_get_pendown_state_gpio;
+		} else {
+			dev_dbg(dev, "Pen down GPIO chip can sleep\n");
+		}
+
+	} else {
 		dev_warn(dev, "Pen down GPIO is not specified in properties\n");
+	}
 
 	return 0;
 }
-- 
2.34.1