linux-kernel - Re: PM regression with LED changes in next-20161109

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Message-ID: <621758ce-dd3f-41ad-d9b8-b8e34538700e@redhat.com>
Date:   Thu, 10 Nov 2016 09:34:52 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Tony Lindgren <tony@...mide.com>,
        Jacek Anaszewski <j.anaszewski@...sung.com>
Cc:     linux-leds@...r.kernel.org, linux-omap@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: PM regression with LED changes in next-20161109

Hi,

On 09-11-16 20:23, Tony Lindgren wrote:
> Hi,
>
> Looks like commit 883d32ce3385 ("leds: core: Add support for poll()ing
> the sysfs brightness attr for changes.") breaks runtime PM for me.
>
> On my omap dm3730 based test system, idle power consumption is over 70
> times higher now with this patch! It goes from about 6mW for the core
> system to over 440mW during idle meaning there's some busy timer now
> active.

Do you have any blinking LEDs or LED triggers defined on the system ?

> Reverting this patch fixes the issue. Any ideas?

All I can think of is something calling led_set_brightness quite often,
the patch in question makes led_set_brightness somewhat more expensive,
but it should not cause such a big difference unless something is
really calling led_set_brightness quite often maybe something is calling
it with the same value all the time ?

Regards,

Hans