linux-kernel - Re: ACPI support in common clock framework

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Message-ID: <152996983664.143105.1441423217241075965@swboyd.mtv.corp.google.com>
Date:   Mon, 25 Jun 2018 16:37:16 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Srinath Mannam <srinath.mannam@...adcom.com>,
        Sudeep Holla <sudeep.holla@....com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Sudeep Holla <sudeep.holla@....com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: ACPI support in common clock framework

Quoting Sudeep Holla (2018-06-25 10:15:45)
> 
> 
> On 25/06/18 17:37, Stephen Boyd wrote:
> > Quoting Rafael J. Wysocki (2018-06-16 08:50:18)
> >> On Fri, Jun 15, 2018 at 7:43 PM, Stephen Boyd <sboyd@...nel.org> wrote:
> >>>
> >>> Is this for clk_enable/disable? What about clk_set_rate() or
> >>> clk_set_phase()? Is ACPI's AML taking care of that?
> >>
> >> That's for clk_enable/disable AFAICS.
> >>
> >> AML doesn't manage device performance states at all.
> > 
> > Alright. We may need to add a better way for device drivers to get
> > handles to clk pointers on ACPI firmware so they can change frequencies
> > or phase, etc. 
> 
> Is there any specific usecase/device needing this in the kernel ? SPI
> slaves ?

Mark Brown has been pushing x86 folks to use clk framework for audio
drivers in ASoC. I haven't seen other uses besides that really.