[PATCH 5.17 0167/1126] media: gpio-ir-tx: fix transmit with long spaces on Orange Pi PC

Greg Kroah-Hartman
2022-04-05T07:47:52Z

From: Sean Young <sean@mess.org>

commit 5ad05ecad4326ddaa26a83ba2233a67be24c1aaa upstream.

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

Cc: stable@vger.kernel.org
Reported-by: Михаил <vrserver1@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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]);