netdev - Re: [PATCH] [RFC] qcom_scm: hide Kconfig symbol

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Message-ID: <YVIsrgKiOG/gFVdT@ripper>
Date:   Mon, 27 Sep 2021 13:42:22 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Rob Clark <robdclark@...il.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Alex Elder <elder@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Maxime Ripard <mripard@...nel.org>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
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        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH] [RFC] qcom_scm: hide Kconfig symbol

On Mon 27 Sep 13:15 PDT 2021, Arnd Bergmann wrote:

> On Mon, Sep 27, 2021 at 9:52 PM Bjorn Andersson
> <bjorn.andersson@...aro.org> wrote:
> > On Mon 27 Sep 08:22 PDT 2021, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd@...db.de>
> > >
> > >  - To avoid a circular dependency chain involving RESET_CONTROLLER
> > >    and PINCTRL_SUNXI, change the 'depends on RESET_CONTROLLER' in
> > >    the latter one to 'select'.
> >
> > Can you please help me understand why this is part of the same patch?
> 
> This can be done as a preparatory patch if we decide to do it this way,
> for the review it seemed better to spell out that this is required.
> 
> I still hope that we can avoid adding another 'select RESET_CONTROLLER'
> if someone can figure out what to do instead.
> 

Okay, thanks.

> The problem here is that QCOM_SCM selects RESET_CONTROLLER,
> and turning that into 'depends on' would in turn mean that any driver that
> wants to select QCOM_SCM would have to have the same RESET_CONTROLLER
> dependency.
> 

Right, and that will just be another thing we'll get wrong across the
tree.

> An easier option might be to find a way to build QCOM_SCM without
> RESET_CONTROLLER for compile testing purposes. I don't know
> what would break from that.
> 

Afaict the reset API is properly stubbed and RESET_CONTROLLER is a bool,
so I think we can simply drop the "select" and the kernel will still
compile fine in all combinations.

When it comes to runtime, we currently select RESET_CONTROLLER from the
Qualcomm common clocks. If that is dropped (why would it...) it seems
possible to build a custom kernel for msm8916 that we can boot and miss
the stubbed out "mss restart" reset line from the SCM.


So, let's just drop the select RESET_CONTROLLER from SCM for now.

Regards,
Bjorn