linux-kernel - RE: [PATCH] clk: imx: imx93: introduce clk

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Date:   Thu, 4 May 2023 11:39:49 +0000
From:   Peng Fan <peng.fan@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Greg KH <greg@...ah.com>,
        "Peng Fan (OSS)" <peng.fan@....nxp.com>,
        Rob Herring <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>
CC:     "abelvesa@...nel.org" <abelvesa@...nel.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] clk: imx: imx93: introduce clk_bypassed module parameter



> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Sent: 2023年5月4日 19:01
> To: Peng Fan <peng.fan@....com>; Greg KH <greg@...ah.com>; Peng Fan
> (OSS) <peng.fan@....nxp.com>; Rob Herring <robh+dt@...nel.org>;
> krzysztof.kozlowski+dt@...aro.org
> Cc: abelvesa@...nel.org; mturquette@...libre.com; sboyd@...nel.org;
> shawnguo@...nel.org; s.hauer@...gutronix.de; kernel@...gutronix.de;
> festevam@...il.com; dl-linux-imx <linux-imx@....com>; linux-
> clk@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> kernel@...r.kernel.org
> 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@...aro.org>
> >> Sent: 2023年5月4日 17:31
> >> To: Peng Fan <peng.fan@....com>; Greg KH <greg@...ah.com>; Peng
> Fan
> >> (OSS) <peng.fan@....nxp.com>; Rob Herring <robh+dt@...nel.org>;
> >> krzysztof.kozlowski+dt@...aro.org
> >> Cc: abelvesa@...nel.org; mturquette@...libre.com; sboyd@...nel.org;
> >> shawnguo@...nel.org; s.hauer@...gutronix.de;
> kernel@...gutronix.de;
> >> festevam@...il.com; dl-linux-imx <linux-imx@....com>; linux-
> >> clk@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> >> kernel@...r.kernel.org
> >> 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@....com>
> >>>>>
> >>>>> 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