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From: John Stultz <>
To: Bjorn Andersson <>
Cc: lkml <>,
	Catalin Marinas <>,
	Will Deacon <>, Andy Gross <>,
	Joerg Roedel <>,
	Thomas Gleixner <>,
	Marc Zyngier <>,
	Linus Walleij <>,
	Vinod Koul <>, Kalle Valo <>,
	Maulik Shah <>,
	Saravana Kannan <>,
	Todd Kjos <>,
	Greg Kroah-Hartman <>,
	linux-arm-msm <>,
	" DRIVERS <>,
	Joerg Roedel <>,"
	"open list:GPIO SUBSYSTEM" <>
Subject: Re: [PATCH] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module
Date: Mon, 19 Jul 2021 12:00:05 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <YPJkF21ItYlKODyq@yoga>

On Fri, Jul 16, 2021 at 10:01 PM Bjorn Andersson
<> wrote:
> On Tue 06 Jul 23:53 CDT 2021, John Stultz wrote:
> > Allow the qcom_scm driver to be loadable as a permenent module.
> >
> > This still uses the "depends on QCOM_SCM || !QCOM_SCM" bit to
> > ensure that drivers that call into the qcom_scm driver are
> > also built as modules. While not ideal in some cases its the
> > only safe way I can find to avoid build errors without having
> > those drivers select QCOM_SCM and have to force it on (as
> > QCOM_SCM=n can be valid for those drivers).
> >
> > Reviving this now that Saravana's fw_devlink defaults to on,
> > which should avoid loading troubles seen before.
> >
> Are you (in this last paragraph) saying that all those who have been
> burnt by fw_devlink during the last months and therefor run with it
> disabled will have a less fun experience once this is merged?

I guess potentially. So way back when this was originally submitted,
some folks had trouble booting if it was set as a module due to it
loading due to the deferred_probe_timeout expiring.
My attempts to change the default timeout value to be larger ran into
trouble, but Saravana's fw_devlink does manage to resolve things
properly for this case.

But if folks are having issues w/ fw_devlink, and have it disabled,
and set QCOM_SCM=m they could still trip over the issue with the
timeout firing before it is loaded (especially if they are loading
modules from late mounted storage rather than ramdisk).

> (I'm picking this up, but I don't fancy the idea that some people are
> turning the boot process into a lottery)

Me neither, and I definitely think the deferred_probe_timeout logic is
way too fragile, which is why I'm eager for fw_devlink as it's a much
less racy approach to handling module loading dependencies.  So if you
want to hold on this, while any remaining fw_devlink issues get
sorted, that's fine.  But I'd also not cast too much ire at
fw_devlink, as the global probe timeout approach for handling optional
links isn't great, and we need a better solution.


  reply	other threads:[~2021-07-19 19:34 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-07  4:53 [PATCH] firmware: QCOM_SCM: Allow qcom_scm driver to be loadable as a permenent module John Stultz
2021-07-17  5:01 ` Bjorn Andersson
2021-07-19 19:00   ` John Stultz [this message]
2021-07-19 19:36     ` Bjorn Andersson
2021-07-19 21:53       ` Saravana Kannan
2021-07-21 20:13         ` Bjorn Andersson
2021-07-21 11:54 ` Greg Kroah-Hartman
2021-07-21 17:24   ` John Stultz
2021-07-21 18:00     ` Saravana Kannan
2021-07-21 20:23       ` Bjorn Andersson
2021-07-21 21:07         ` Saravana Kannan
2021-07-23 14:24           ` Bjorn Andersson
2021-07-23 12:21     ` Greg Kroah-Hartman

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