RE: [PATCH] clk: imx: imx93: introduce clk_bypassed module parameter

[Peng Fan]

> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> Sent: 2023年5月4日 19:01
> To: Peng Fan <peng.fan@xxxxxxx>; Greg KH <greg@xxxxxxxxx>; Peng Fan
> (OSS) <peng.fan@xxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>;
> krzysztof.kozlowski+dt@xxxxxxxxxx
> Cc: abelvesa@xxxxxxxxxx; mturquette@xxxxxxxxxxxx; sboyd@xxxxxxxxxx;
> shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx;
> festevam@xxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; linux-
> clk@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] clk: imx: imx93: introduce clk_bypassed module
> parameter
> 
> On 04/05/2023 11:34, Peng Fan wrote:
> >
> >
> >> -----Original Message-----
> >> From: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> >> Sent: 2023年5月4日 17:31
> >> To: Peng Fan <peng.fan@xxxxxxx>; Greg KH <greg@xxxxxxxxx>; Peng
> Fan
> >> (OSS) <peng.fan@xxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>;
> >> krzysztof.kozlowski+dt@xxxxxxxxxx
> >> Cc: abelvesa@xxxxxxxxxx; mturquette@xxxxxxxxxxxx; sboyd@xxxxxxxxxx;
> >> shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx;
> >> festevam@xxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>; linux-
> >> clk@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> >> kernel@xxxxxxxxxxxxxxx
> >> Subject: Re: [PATCH] clk: imx: imx93: introduce clk_bypassed module
> >> parameter
> >>
> >> On 04/05/2023 11:17, Peng Fan wrote:
> >>> + DT maintainers.
> >>>
> >>>> Subject: Re: [PATCH] clk: imx: imx93: introduce clk_bypassed module
> >>>> parameter
> >>>>
> >>>> On Thu, May 04, 2023 at 04:55:06PM +0800, Peng Fan (OSS) wrote:
> >>>>> From: Peng Fan <peng.fan@xxxxxxx>
> >>>>>
> >>>>> With the clk names specified in clk_bypassed module parameter,
> >>>>> give user an option to bypass the clk from managing them by Linux
> kernel.
> >>>>
> >>>> As I said on another email, no, please do not add new module
> >>>> parameters for drivers, this is not the 1990s
> >>>
> >>> ok, but this is for boot, so only DT could be considered.
> >>>
> >>> But DT is to describe hardware, here I just wanna give user an
> >>> option to bypass some clocks. Is it ok to add a DT property saying
> >>> "fsl,imx93-bypass-clks = <IMX93_CLK_X>, <IMX93_CLK_Y>" ?
> >>>
> >>
> >> I don't know what it is to "bypass some clocks". This does not look
> >> like parameter for system at all.
> >
> > Currently the linux clk driver registers all the clocks and manage them.
> > But when M33 is running, M33 may not wanna linux to manage some
> clocks
> > M33 is using. So I wanna linux not register those clocks that M33 will
> > use.
> 
> Ask the one who designed such system that second processor pokes parts
> of first processor... I assume if the clock controller is enabled in DTS for
> Linux, then the Linux owns it. Otherwise how do you expect to handle
> concurrent access to same registers from different processors?

Each clock has a register, we suppose M33 SW and Linux SW not concurrent
access to same register.
> 
> And how are you going to decide which clocks should be managed by M33?
> One firmware could want to play with one clock, other with everything...
> Module parameter is not the way to deal with it.

Actually I have no good idea.

> 
> Probably Ahmad's idea is the only one reasonable in your case, if you do not
> have hypervisor.

No hypervisor here. Anyway let me think about more.

Thanks,
Peng.

> 
> 
> Best regards,
> Krzysztof