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

[Anson Huang]

Hi, Stephen

Anson Huang
Best Regards!


> -----Original Message-----
> From: Stephen Boyd <sboyd@xxxxxxxxxx>
> Sent: Saturday, October 13, 2018 3:48 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 Anson Huang (2018-10-08 01:34:59)
> > > Quoting Anson Huang (2018-09-03 00:20:53)
> > > > > > 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.
> > > >
> > >
> > > Why can't we add clks to the op-tee node in DT's /firmware container?
> > > Then any clks in there can be turned on forever and left enabled by
> > > the linux driver?
> >
> > I did NOT run op-tee with Linux-next kernel before, can you advise more?
> 
> Neither have I, so I can't advise more.
> 
> > And I think if op-tee has such requirement, can we have another patch
> > to cover it?
> 
> Yes.
> 
> 
> > I believe all other i.MX platforms also have same requirements if
> > considering op-tee support, so I think it should be another topic, what do you
> think?
> >
> 
> I'm going to drop these patches from my review queue. Please resend them
> and please include the op-tee patches too.


I do NOT know how to include the op-tee patch to meet special requirement, should
the op-tee related patch be added later when someone actually add the op-tee support for i.MX7?
It should NOT block this patch set, do you think we can add this patch set first?

Anson.