[PATCH 4.14 42/91] media: gpio-ir-tx: improve precision of transmitted signal due to scheduling

Greg Kroah-Hartman
2020-09-01T16:59:36Z

From: Sean Young <sean@mess.org>

[ Upstream commit ea8912b788f8144e7d32ee61e5ccba45424bef83 ]

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 udelay().

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 cd476cab97820..4e70b67ccd181 100644
--- a/drivers/media/rc/gpio-ir-tx.c
+++ b/drivers/media/rc/gpio-ir-tx.c
@@ -87,13 +87,8 @@ 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]);
--
2.25.1