On Thu, Nov 09, 2017 at 02:37:40PM -0800, Tony Lindgren wrote:
> * Ladislav Michl <ladis@xxxxxxxxxxxxxx> [171109 22:33]:
> > On Thu, Nov 09, 2017 at 01:57:07PM -0800, Tony Lindgren wrote:
> > > Maybe you can block idle states from your driver with PM QoS?
> > >
> > > Just add some latency requirement. See for example what was done
> > > earlier for omap3 audio in commit 9834ffd1ecc3 ("ASoC: omap-mcbsp: Add PM
> > > QoS support for McBSP to prevent glitches").
> > >
> > > Not sure if we can do this in a generic way.. But maybe it's doable for
> > > things like PWM drivers.
> >
> > That seems to be rather problematic as I need this for generic driver:
> > drivers/media/rc/gpio-ir-recv.c
> > I need to be able to detect key presses of various remotes, so protocol
> > is unknown in advance. Having such a big jitter leads to false positives
> > when guessing protocol or decoding errors.
> >
> > I was also considering using FIQ handler, but it probably won't help in
> > this case.
>
> Hmm to me it seems that PM QoS would be totally justified for a driver
> like that.
So, looked at above mentioned commit and tried patch bellow without any
noticeable change. Also PM QoS seems to handle DMA and network latency only.
I need to handle IRQ latency. Any other options?
Thank you,
ladis
diff --git a/drivers/media/rc/gpio-ir-recv.c b/drivers/media/rc/gpio-ir-recv.c
index b6c4a2d2b696..5c580bf70ff8 100644
--- a/drivers/media/rc/gpio-ir-recv.c
+++ b/drivers/media/rc/gpio-ir-recv.c
@@ -19,6 +19,7 @@
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/platform_device.h>
+#include <linux/pm_qos.h>
#include <linux/irq.h>
#include <media/rc-core.h>
@@ -92,6 +93,10 @@ static int gpio_ir_recv_probe(struct platform_device *pdev)
gpio_dev->rcdev = rcdev;
+ rc = dev_pm_qos_expose_latency_limit(dev, 10);
+ if (rc < 0)
+ return rc;
+
rc = devm_rc_register_device(dev, rcdev);
if (rc < 0) {
dev_err(dev, "failed to register rc device (%d)\n", rc);
--
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