RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array

[Anson Huang]

Gentle Ping...

Anson Huang
Best Regards!


> -----Original Message-----
> From: Anson Huang
> Sent: Monday, September 3, 2018 3:21 PM
> To: Stephen Boyd <sboyd@xxxxxxxxxx>; kernel@xxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-clk@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; mturquette@xxxxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; shawnguo@xxxxxxxxxx; Fabio Estevam
> <fabio.estevam@xxxxxxx>; Jerome Forissier <jerome.forissier@xxxxxxxxxx>;
> Peng Fan <peng.fan@xxxxxxx>; Rob Herring <robh@xxxxxxxxxx>
> Cc: dl-linux-imx <linux-imx@xxxxxxx>
> Subject: RE: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array
> 
> 
> 
> Anson Huang
> Best Regards!
> 
> 
> > -----Original Message-----
> > From: Stephen Boyd <sboyd@xxxxxxxxxx>
> > Sent: Saturday, September 1, 2018 1:58 AM
> > To: kernel@xxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > linux-clk@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > mturquette@xxxxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> shawnguo@xxxxxxxxxx;
> > Anson Huang <anson.huang@xxxxxxx>; Fabio Estevam
> > <fabio.estevam@xxxxxxx>; Jerome Forissier
> > <jerome.forissier@xxxxxxxxxx>; Peng Fan <peng.fan@xxxxxxx>; Rob
> > Herring <robh@xxxxxxxxxx>
> > Cc: dl-linux-imx <linux-imx@xxxxxxx>
> > Subject: Re: [PATCH 2/2] clk: imx: imx7d: remove clks_init_on array
> >
> > Quoting Jerome Forissier (2018-08-31 01:01:44)
> > >
> > >
> > > On 08/31/2018 03:29 AM, Stephen Boyd wrote:
> > > > Quoting Peng Fan (2018-08-12 18:15:41)
> > > >> Hi Anson,
> > > >>
> > > >>>>> -----Original Message-----
> > > >>>>> From: Anson Huang
> > > >>>>> Sent: 2018å8æ8æ 12:39
> > > >>>>> To: shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> > > >>>>> kernel@xxxxxxxxxxxxxx; Fabio Estevam <fabio.estevam@xxxxxxx>;
> > > >>>>> mturquette@xxxxxxxxxxxx; sboyd@xxxxxxxxxx;
> > > >>>>> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> > > >>>>> linux-clk@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > > >>>>> Cc: dl-linux-imx <linux-imx@xxxxxxx>
> > > >>>>> 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?
> > >
> > > Sounds reasonable, but how could this be done without introducing
> > > platform-specific stuff in the OP-TEE driver?
> > >
> >
> > Why is that a goal?
> 
> I do NOT think we should consider such case in this patch series, whatever
> OP-TEE needs for its own feature, it should do necessary operations either in its
> driver or somewhere else by adding new patch.
> 
> Anson.