From mboxrd@z Thu Jan 1 00:00:00 1970 From: swarren@wwwdotorg.org (Stephen Warren) Date: Tue, 06 May 2014 10:26:09 -0600 Subject: [PATCH v3 1/3] base: power: Add generic OF-based power domain look-up In-Reply-To: References: <1398271618-28932-1-git-send-email-t.figa@samsung.com> <1398271618-28932-2-git-send-email-t.figa@samsung.com> <535E9163.3070305@wwwdotorg.org> Message-ID: <53690D21.8080807@wwwdotorg.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 05/06/2014 02:22 AM, Ulf Hansson wrote: > On 28 April 2014 19:35, Stephen Warren wrote: >> On 04/23/2014 10:46 AM, Tomasz Figa wrote: >>> This patch introduces generic code to perform power domain look-up using >>> device tree and automatically bind devices to their power domains. >>> Generic device tree binding is introduced to specify power domains of >>> devices in their device tree nodes. >>> >>> Backwards compatibility with legacy Samsung-specific power domain >>> bindings is provided, but for now the new code is not compiled when >>> CONFIG_ARCH_EXYNOS is selected to avoid collision with legacy code. This >>> will change as soon as Exynos power domain code gets converted to use >>> the generic framework in further patch. >> >>> diff --git a/Documentation/devicetree/bindings/power/power_domain.txt b/Documentation/devicetree/bindings/power/power_domain.txt >> >>> +==Power domain consumers== >>> + >>> +Required properties: >>> + - power-domain : A phandle and power domain specifier as defined by bindings >>> + of power controller specified by phandle. >> >> It seems quite likely that a single logical device could have components >> in multiple power domains. Consider an HDMI controller with different >> power domains for the HDMI core, CEC communication, DDC/I2C >> communication, and the I/O pads, with no clear separation between those >> two components of the module (no separate register spaces, but the >> bits/registers are interleaved all together). >> >> As such, I think that rather than a "power-domain" property, we need a >> pair of "power-domains", and "power-domain-names" properties, and >> preferably with mandatory usage of name-based lookups, rather than >> allowing a random mix of name-based and index-based lookups like we have >> with some existing resource bindings. > > Each struct device have only one dev_pm_domain pointer, thus a device > are not able to reside in more than one power domain. > > Therefore I doubt this will be very useful, unless I missed your point. :-) A struct device is a Linux-internal concept. DT is supposed to represent the HW in an OS-agnostic fashion, not according to the limitations of any one OS's driver model. It's certainly true that a single logical HW module (represented by a single DT node) can have parts in multiple power domains.