linux-kernel - Re: [PATCH 4/7] ARM: OMAP2+: powerdomain: introduce logic for finding valid power domain

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Date:	Wed, 27 Aug 2014 11:27:38 -0700
From:	Kevin Hilman <khilman@...prootsystems.com>
To:	Nishanth Menon <nm@...com>
Cc:	Tony Lindgren <tony@...mide.com>, Tero Kristo <t-kristo@...com>,
	Paul Walmsley <paul@...an.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Keerthy <j-keerthy@...com>,
	Benoît Cousson <bcousson@...libre.com>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: Re: [PATCH 4/7] ARM: OMAP2+: powerdomain: introduce logic for finding valid power domain

Nishanth Menon <nm@...com> writes:

> powerdomain configuration in OMAP is done using PWRSTCTRL register for
> each power domain. However, PRCM lets us write any value we'd like to
> the logic and power domain target states, however the SoC integration
> tends to actually function only at a few discrete states. These valid
> states are already in our powerdomains_xxx_data.c file.
>
> So, provide a function to easily query valid low power state that the
> power domain is allowed to go to.
>
> Based on work originally done by Jean Pihet <j-pihet@...com>
> https://patchwork.kernel.org/patch/1325091/ . There is no attempt to
> create a new powerdomain solution here, except fixing issues seen
> attempting invalid programming attempts. Future consolidation to the
> generic powerdomain framework should consider this requirement as
> well.
>
> Similar solutions have been done in product kernels in the past such
> as:
> https://android.googlesource.com/kernel/omap.git/+blame/android-omap-panda-3.0/arch/arm/mach-omap2/pm44xx.c
>
> Signed-off-by: Nishanth Menon <nm@...com>
> ---

nit: this is part of a fixes series, but it's more of a new feature.

That being said, the feature is needed and looks OK, except for...

> +up_search:
> +	/* OK, no deeper ones, can we get a higher match? */
> +	new_pwrst = req_state + 1;
> +	while (!(pwrdm_states & BIT(new_pwrst))) {
> +		/* BUG if we have messed up database */
> +		BUG_ON(new_pwrst > PWRDM_POWER_ON);

I don't think this is BUG() worthy, and should have a saner way to recover.

Kevin
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