linux-kernel - [PATCH 5.16 0172/1017] media: gpio-ir-tx: fix transmit with long spaces on Orange Pi PC

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Message-Id: <20220405070359.334460978@linuxfoundation.org>
Date:   Tue,  5 Apr 2022 09:18:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Михаил 
        <vrserver1@...il.com>, Sean Young <sean@...s.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: [PATCH 5.16 0172/1017] media: gpio-ir-tx: fix transmit with long spaces on Orange Pi PC

From: Sean Young <sean@...s.org>

commit 5ad05ecad4326ddaa26a83ba2233a67be24c1aaa upstream.

Calling udelay for than 1000us does not always yield the correct
results.

Cc: stable@...r.kernel.org
Reported-by: Михаил <vrserver1@...il.com>
Signed-off-by: Sean Young <sean@...s.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/media/rc/gpio-ir-tx.c |   28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

--- a/drivers/media/rc/gpio-ir-tx.c
+++ b/drivers/media/rc/gpio-ir-tx.c
@@ -48,11 +48,29 @@ static int gpio_ir_tx_set_carrier(struct
 	return 0;
 }
 
+static void delay_until(ktime_t until)
+{
+	/*
+	 * delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
+	 * m68k ndelay(s64) does not compile; so use s32 rather than s64.
+	 */
+	s32 delta;
+
+	while (true) {
+		delta = ktime_us_delta(until, ktime_get());
+		if (delta <= 0)
+			return;
+
+		/* udelay more than 1ms may not work */
+		delta = min(delta, 1000);
+		udelay(delta);
+	}
+}
+
 static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
 				   uint count)
 {
 	ktime_t edge;
-	s32 delta;
 	int i;
 
 	local_irq_disable();
@@ -63,9 +81,7 @@ static void gpio_ir_tx_unmodulated(struc
 		gpiod_set_value(gpio_ir->gpio, !(i % 2));
 
 		edge = ktime_add_us(edge, txbuf[i]);
-		delta = ktime_us_delta(edge, ktime_get());
-		if (delta > 0)
-			udelay(delta);
+		delay_until(edge);
 	}
 
 	gpiod_set_value(gpio_ir->gpio, 0);
@@ -97,9 +113,7 @@ static void gpio_ir_tx_modulated(struct
 		if (i % 2) {
 			// space
 			edge = ktime_add_us(edge, txbuf[i]);
-			delta = ktime_us_delta(edge, ktime_get());
-			if (delta > 0)
-				udelay(delta);
+			delay_until(edge);
 		} else {
 			// pulse
 			ktime_t last = ktime_add_us(edge, txbuf[i]);