linux-kernel - Re: [PATCH] ARM: OMAP2+: omap_device: add fail hook for runtime

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Message-ID: <871u1k8uyf.fsf@linaro.org>
Date:	Tue, 10 Dec 2013 09:41:28 -0800
From:	Kevin Hilman <khilman@...aro.org>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Nishanth Menon <nm@...com>, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Tobias Jakobi <tjakobi@...h.uni-bielefeld.de>,
	Joel F <joelf@...com>
Subject: Re: [PATCH] ARM: OMAP2+: omap_device: add fail hook for runtime_pm when bad data is detected

Tony Lindgren <tony@...mide.com> writes:

> * Kevin Hilman <khilman@...aro.org> [131209 08:07]:
>> Tony Lindgren <tony@...mide.com> writes:
>> 
>> > * Nishanth Menon <nm@...com> [131203 17:40]:
>> >> Due to the cross dependencies between hwmod for automanaged device
>> >> information for OMAP and dts node definitions, we can run into scenarios
>> >> where the dts node is defined, however it's hwmod entry is yet to be
>> >> added. In these cases:
>> >> a) omap_device does not register a pm_domain (since it cannot find
>> >>    hwmod entry).
>> >> b) driver does not know about (a), does a pm_runtime_get_sync which
>> >>    never fails
>> >> c) It then tries to do some operation on the device (such as read the
>> >>   revision register (as part of probe) without clock or adequate OMAP
>> >>   generic PM operation performed for enabling the module.
>> >> 
>> >> This causes a crash such as that reported in:
>> >> https://bugzilla.kernel.org/show_bug.cgi?id=66441
>> >> 
>> >> When 'ti,hwmod' is provided in dt node, it is expected that the device
>> >> will not function without the OMAP's power automanagement. Hence, when
>> >> we hit a fail condition (due to hwmod entries not present or other
>> >> similar scenario), fail at pm_domain level due to lack of data, provide
>> >> enough information for it to be fixed, however, it allows for the driver
>> >> to take appropriate measures to prevent crash.
>> >
>> > Kevin, any comments on this one?
>> 
>> Looks like a good approach to catch these corner cases.
>> 
>> Acked-by: Kevin Hilman <khilman@...aro.org>
>
> Kevin, care to apply this directly?
>
> Acked-by: Tony Lindgren <tony@...mide.com> 

Applied.

Kevin
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