linux-kernel - Re: [PATCH 6/9] ARM: tegra: Export tegra_powergate_power

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Date:	Thu, 19 Jun 2014 11:02:35 +0300
From:	Peter De Schrijver <pdeschrijver@...dia.com>
To:	Stephen Warren <swarren@...dotorg.org>
CC:	Thierry Reding <thierry.reding@...il.com>,
	Mikko Perttunen <mperttunen@...dia.com>,
	"tj@...nel.org" <tj@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>
Subject: Re: [PATCH 6/9] ARM: tegra: Export tegra_powergate_power_on

On Wed, Jun 18, 2014 at 05:37:54PM +0200, Stephen Warren wrote:
> On 06/18/2014 06:18 AM, Peter De Schrijver wrote:
> > On Tue, Jun 17, 2014 at 11:51:20PM +0200, Thierry Reding wrote:
> >> * PGP Signed by an unknown key
> >>
> >> On Tue, Jun 17, 2014 at 05:01:46PM +0300, Peter De Schrijver wrote:
> >>> On Tue, Jun 17, 2014 at 02:13:15PM +0200, Thierry Reding wrote:
> >>>>> Old Signed by an unknown key
> >>>>
> >>>> On Mon, Jun 16, 2014 at 04:01:02PM -0600, Stephen Warren wrote:
> >>>>> On 06/04/2014 05:32 AM, Mikko Perttunen wrote:
> >>>>>> This symbol needs to be exported to power on rails without using
> >>>>>> tegra_powergate_sequence_power_up. tegra_powergate_sequence_power_up
> >>>>>> cannot be used in situations where the driver wants to handle clocking
> >>>>>> by itself.
> >>>>>
> >>>>> Thierry, are you OK with this change?
> >>>>
> >>>> I would've preferred tegra_powergate_sequence_power_up() to be used
> >>>
> >>> I don't think the current tegra_powergate_sequence_power_up() API is very well
> >>> defined though. I don't think the clocks and resets required by the sequence
> >>> should be provided by the driver. For one, there can be several clocks and
> >>> resets that need to be controlled for a single domain.
> >>
> >> Do you have any suggestions for what the API should look like? Even if
> >> we plan to move to some different API, I think there's some advantage in
> >> using it consistently if for no other reason than to make it easier to
> >> replace occurrences later on.
> >>
> > 
> > I think the API should only have the domain ID as input so:
> > 
> > int tegra_powerdomain_on(int id) 
> > 
> > /*
> >  * Prerequisites: domain is off
> >  * Result: domain is on, clocks of the modules in the domain are off, modules are in reset
> >  */
> > 
> > int tegra_powerdomain_off(int id)
> > 
> > /*
> >  * Prerequisites: all clocks of the modules in the domain are off
> >  * result: domain is off
> >  */
> 
> That doesn't make sense; the PMC doesn't have access to the clock and
> reset IDs - that's why the API requires them to be passed in.
> 

We should make driver look them up by name then. It doesn't make sense to
move this knowledge to the drivers as there can be several modules in 1
powerdomain. So every driver would then need to have access to all clock
and reset IDs of the modules of the domain?

Cheers,

Peter.
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