linux-kernel - Re: [PATCH v2 3/5] ARM: bcm2835: add rpi power domain driver

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Message-ID: <7hmvtln87l.fsf@deeprootsystems.com>
Date:	Mon, 07 Dec 2015 15:35:10 -0800
From:	Kevin Hilman <khilman@...nel.org>
To:	Eric Anholt <eric@...olt.net>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Stephen Warren <swarren@...dotorg.org>,
	Lee Jones <lee@...nel.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Aring <alex.aring@...il.com>,
	devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>
Subject: Re: [PATCH v2 3/5] ARM: bcm2835: add rpi power domain driver

Eric Anholt <eric@...olt.net> writes:

> From: Alexander Aring <alex.aring@...il.com>
>
> This patch adds support for several power domains on Raspberry Pi,
> including USB (so it can be enabled even if the bootloader didn't do
> it), and graphics.
>
> This patch is the combined work of Eric Anholt (who wrote USB support
> inside of the Raspberry Pi firmware driver, and wrote the non-USB
> domain support) and Alexander Aring (who separated the original USB
> work out from the firmware driver).
>
> Signed-off-by: Alexander Aring <alex.aring@...il.com>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>
> v2: Add support for power domains other than USB, using the new
>     firmware interface, reword commit message (changes by Eric)

[...]

> +/*
> + * Firmware indices for the old power domains interface.  Only a few
> + * of them were actually implemented.
> + */
> +#define RPI_OLD_POWER_DOMAIN_USB		3
> +#define RPI_OLD_POWER_DOMAIN_V3D		10
> +

Is "old" the right word here?  Are there firmware versions that could be
used instead?  What happens when the firwmware is updated next time?

[...]

> +	/*
> +	 * Use the old firmware interface for USB power, so that we
> +	 * can turn it on even if the firmware hasn't been updated.
> +	 */
> +	rpi_init_old_power_domain(rpi_domains, RPI_POWER_DOMAIN_USB,
> +				  RPI_OLD_POWER_DOMAIN_USB, "USB");

This seems a bit restrictive.

To me, it seems that determining "old" or "new" (or revision of fw
interface to use) should be described in DT, not hard-coded in the power
domain driver.

What about an additional DT property to describe that? or possibly
another cell in the domain which could be used to optionally set
old/legacy.

Kevin
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