RE: Question: why call clk_prepare in pm_clk_acquire

From: Peng Fan <peng.fan@nxp.com>
To: Sudeep Holla <sudeep.holla@arm.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
	"ben.dooks@codethink.co.uk" <ben.dooks@codethink.co.uk>,
	"rafael.j.wysocki@intel.com" <rafael.j.wysocki@intel.com>,
	"dmitry.baryshkov@linaro.org" <dmitry.baryshkov@linaro.org>,
	"jonathanh@nvidia.com" <jonathanh@nvidia.com>,
	"npitre@baylibre.com" <npitre@baylibre.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Aisheng Dong <aisheng.dong@nxp.com>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Dien Pham <dien.pham.ry@renesas.com>
Subject: RE: Question: why call clk_prepare in pm_clk_acquire
Date: Thu, 15 Sep 2022 00:59:32 +0000	[thread overview]
Message-ID: <DU0PR04MB94178803DCB15BBA18E32B1F88499@DU0PR04MB9417.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <20220914153038.inbch35g7ldsyzhx@bogus>

> Subject: Re: Question: why call clk_prepare in pm_clk_acquire
> 
> On Mon, Sep 12, 2022 at 06:58:49PM +0100, Geert Uytterhoeven wrote:
> > Hi Sudeep,
> >
> > CC Dien Pham
> >
> > On Mon, Sep 12, 2022 at 6:49 PM Geert Uytterhoeven <geert@linux-
> m68k.org> wrote:
> > > On Fri, Sep 9, 2022 at 4:51 PM Sudeep Holla <sudeep.holla@arm.com>
> wrote:
> > > > On Fri, Sep 09, 2022 at 01:12:03PM +0200, Ulf Hansson wrote:
> > > > > On Thu, 8 Sept 2022 at 19:38, Sudeep Holla <sudeep.holla@arm.com>
> wrote:
> > > > > > On Thu, Sep 08, 2022 at 04:37:13PM +0200, Ulf Hansson wrote:
> > > > > > > On Thu, 8 Sept 2022 at 09:33, Peng Fan <peng.fan@nxp.com>
> wrote:
> > > > > > > > We are facing an issue clk_set_rate fail with commit
> a3b884cef873 ("firmware:
> > > > > > > > arm_scmi: Add clock management to the SCMI power domain")
> > > > > > > > ,
> > > > > > >
> > > > > > > Hmm, I wonder about the main reason behind that commit. Can
> > > > > > > we revert it or is there some platform/driver that is really relying
> on it?
> > > > > > >
> > > > > >
> > > > > > IIUC, at the time of the commit, it was needed on some Renesas
> platform.
> > > > > > Not sure if it is still used or not.
> > > > >
> > > > > Okay! Maybe Nico remembers more, as he authored the patch...
> > > > >
> > > >
> > > > May be, or even check with Renesas team who tested his patch.
> > >
> > > I'm not aware of Renesas platforms using SCMI...
> >
> > Upon closer look, Diep Pham did report a build issue in the SCMI code,
> > so perhaps Diep knows more...
> >
> 
> Yes indeed, Diep Pham tested the original patch IIRC and also has reported
> few bugs in SCMI clock code which are fixed. Hence I know it is used by
> Renesas.
> 
> Hi Peng,
> 
> Absence of DTS changes indicate nothing. I am aware of couple of vendors
> who use SCMI on several platforms and do report issues regularly and help
> in review of the code. So DTS is not a good indicator of SCMI usage
> unfortunately. On reason could be that since it is a firmware, bootloaders
> can detect and update DTS, just my thought and may differ from the reality.

Could we make the GENPD_FLAG_PM_CLK as a optional flag as Ulf suggested?
Such as non scmi clk platforms not require this flag, or any other suggestion?

Regards,
Peng.

> 
> --
> Regards,
> Sudeep