[PATCH 1/2] media: rc: improve precision of transmitted signal due to scheduling

[PATCH 1/2] media: rc: improve precision of transmitted signal due to scheduling

[Sean Young]

usleep_range() may take longer than the max argument due to scheduling,
especially under load. This is causing random errors in the transmitted
IR. Remove the usleep_range() in favour of busy-looping with ndelay().

Signed-off-by: Sean Young <sean@mess.org>
---
 drivers/media/rc/gpio-ir-tx.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/media/rc/gpio-ir-tx.c b/drivers/media/rc/gpio-ir-tx.c
index 18ca12d78314c..66703989ae185 100644
--- a/drivers/media/rc/gpio-ir-tx.c
+++ b/drivers/media/rc/gpio-ir-tx.c
@@ -79,13 +79,8 @@ static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
 			// space
 			edge = ktime_add_us(edge, txbuf[i]);
 			delta = ktime_us_delta(edge, ktime_get());
-			if (delta > 10) {
-				spin_unlock_irqrestore(&gpio_ir->lock, flags);
-				usleep_range(delta, delta + 10);
-				spin_lock_irqsave(&gpio_ir->lock, flags);
-			} else if (delta > 0) {
+			if (delta > 0)
 				udelay(delta);
-			}
 		} else {
 			// pulse
 			ktime_t last = ktime_add_us(edge, txbuf[i]);
-- 
2.26.2

[PATCH 2/2] media: gpio-ir-tx: allow transmission without carrier

[Sean Young]

Some IR protocols do not use a carrier.

Signed-off-by: Sean Young <sean@mess.org>
---
 drivers/media/rc/gpio-ir-tx.c | 56 +++++++++++++++++++++++++++++++----
 1 file changed, 50 insertions(+), 6 deletions(-)

diff --git a/drivers/media/rc/gpio-ir-tx.c b/drivers/media/rc/gpio-ir-tx.c
index 66703989ae185..cd3f284b2f6d6 100644
--- a/drivers/media/rc/gpio-ir-tx.c
+++ b/drivers/media/rc/gpio-ir-tx.c
@@ -42,18 +42,51 @@ static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
 {
 	struct gpio_ir *gpio_ir = dev->priv;
 
-	if (!carrier)
-		return -EINVAL;
-
 	gpio_ir->carrier = carrier;
 
 	return 0;
 }
 
-static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
-		      unsigned int count)
+static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
+				   uint count)
+{
+	unsigned long flags;
+	ktime_t edge;
+	/*
+	 * 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;
+	int i;
+
+	spin_lock_irqsave(&gpio_ir->lock, flags);
+
+	edge = ktime_get();
+
+	for (i = 0; i < count; i++) {
+		if (i % 2) {
+			// space
+			edge = ktime_add_us(edge, txbuf[i]);
+			delta = ktime_us_delta(edge, ktime_get());
+			if (delta > 0)
+				udelay(delta);
+		} else {
+			// pulse
+			gpiod_set_value(gpio_ir->gpio, 1);
+			edge = ktime_add_us(edge, txbuf[i]);
+			delta = ktime_us_delta(edge, ktime_get());
+			if (delta > 0)
+				udelay(delta);
+			gpiod_set_value(gpio_ir->gpio, 0);
+		}
+	}
+
+	spin_unlock_irqrestore(&gpio_ir->lock, flags);
+}
+
+static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
+				 uint count)
 {
-	struct gpio_ir *gpio_ir = dev->priv;
 	unsigned long flags;
 	ktime_t edge;
 	/*
@@ -105,6 +138,17 @@ static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
 	}
 
 	spin_unlock_irqrestore(&gpio_ir->lock, flags);
+}
+
+static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
+		      unsigned int count)
+{
+	struct gpio_ir *gpio_ir = dev->priv;
+
+	if (gpio_ir->carrier)
+		gpio_ir_tx_modulated(gpio_ir, txbuf, count);
+	else
+		gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
 
 	return count;
 }
-- 
2.26.2