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Date:   Thu, 30 Aug 2018 18:29:07 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Anson Huang <anson.huang@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Peng Fan <peng.fan@....com>, Rob Herring <robh@...nel.org>
Cc:     dl-linux-imx <linux-imx@....com>
Subject: RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array

Quoting Peng Fan (2018-08-12 18:15:41)
> Hi Anson,
> 
> > > > -----Original Message-----
> > > > From: Anson Huang
> > > > Sent: 2018年8月8日 12:39
> > > > To: shawnguo@...nel.org; s.hauer@...gutronix.de;
> > > > kernel@...gutronix.de; Fabio Estevam <fabio.estevam@....com>;
> > > > mturquette@...libre.com; sboyd@...nel.org;
> > > > linux-arm-kernel@...ts.infradead.org;
> > > > linux-clk@...r.kernel.org; linux-kernel@...r.kernel.org
> > > > Cc: dl-linux-imx <linux-imx@....com>
> > > > Subject: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array
> > > >
> > > > Clock framework will enable those clocks registered with
> > > > CLK_IS_CRITICAL flag, so no need to have clks_init_on array during
> > > > clock
> > > initialization now.
> > >
> > > Will it be more flexible to parse dts saying "critical-clocks = <xxx>"
> > > or "init-on-arrary=<xxx>"
> > > and enable those clocks?
> > 
> > Parsing the clocks arrays from dtb is another way of enabling critical clocks, but
> > for current i.MX6/7 platforms, we implement it in same way as most of other
> > SoCs, currently I did NOT see any necessity of putting them in dtb, just adding
> > flag during clock registering is more simple, if there is any special requirement
> > for different clocks set to be enabled, then we can add support to enable the
> > method of parsing critical-clocks from dtb. Just my two cents.
> 
> Thinking about OP-TEE want to use one device, but it's clocks are registered
> by Linux, because there is no module in Linux side use it, it will shutdown the clock,
> which cause OP-TEE could not access the device.
> 
> Then people have to modify clk code to add CLK_IS_CRITICAL flag to make sure
> the clocks are not shutdown by Linux.
> 
> However adding a new property in clk node and let driver code parse the dts,
> there is no need to modify clk driver code when OP-TEE needs another device clock.
> 

If OP-TEE needs linux to keep things on then why can't the OP-TEE driver
in Linux probe, acquire clocks, and keep the clks enabled forever?

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