Re: EHCI and MUSB do not discover devices without CONFIG_PM

[Felipe Balbi <felipe.balbi-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

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Hi,

Ladislav Michl <ladis-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org> writes:
> On Tue, Nov 28, 2017 at 08:33:28AM +0100, Greg KH wrote:
>> On Mon, Nov 27, 2017 at 11:08:33PM +0100, Ladislav Michl wrote:
>> > Hi there,
>> > 
>> > USB hosts do not discover any connected device on OMAP3 based board
>> > with CONFIG_PM=n. Just enabling this option is enough to restore working
>> > behaviour. Nothing unusual in log. Tested 4.14.2 and 4.15-rc1. I know
>> > a lot of stuff depends on CONFIG_PM, but is this expected behaviour?
>> > Neither EHCI nor MUSB is working without CONFIG_PM.
>> 
>> What bus type is your controllers on?  PCI?  platform?  Something else?
>
> Platform controllers inside OMAP3630 Soc.
>
>> And yes, perhaps this is to be expected, why would you not want
>> CONFIG_PM to be enabled?  :)
>
> For a start, I know Linux is general purpose OS and I know I cannot expect
> low latency or low jitter when dealing with interrupts.
>
> Original problem is described here:
> https://www.spinics.net/lists/linux-omap/msg140081.html
>
> Shortly, with CONFIG_PM jitter of GPIO interrupt is about 350us which
> renders IR receiver unuseable - is cannot reliably decode IR protocol
> (gpio-ir-recv is used). With CONFIG_PM disabled, jitter is around 30us
> and that's enough to make IR decoders work.
>
> And as I was unable to fix it, nor anyone provided useful hint, I though
> I could work around problem from another side. And here we are...

Isn't it enough to just set a huge timeout for GPIO's runtime_pm? You
can do that through sysfs. Just write a big number to the GPIO's
autosuspend_delay_ms file. This should help you:

modified   drivers/gpio/gpio-omap.c
@@ -1238,6 +1238,8 @@ static int omap_gpio_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, bank);
 
+	pm_runtime_use_autosuspend(dev);
+	pm_runtime_set_autosuspend_delay(dev, 60000);
 	pm_runtime_enable(dev);
 	pm_runtime_irq_safe(dev);
 	pm_runtime_get_sync(dev);


-- 
balbi

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