Re: EHCI and MUSB do not discover devices without CONFIG_PM

[Ladislav Michl <ladis-6z/3iImG2C8G8FEW9MqTrA@public.gmane.org>]

On Tue, Nov 28, 2017 at 11:03:50AM +0200, Felipe Balbi wrote:
> 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:

That does not help. And I already have Tony's hack in the patch stack:
https://patchwork.kernel.org/patch/9643499/
So this part of SoC is not powered off at all.

> 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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