linux-kernel - Re: [PATCH 0/4] of: property: fw

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Message-ID: <69b79028764dcdfc9f550a5f95752afb491005f0.camel@suse.de>
Date:   Thu, 16 Apr 2020 13:02:59 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] of: property: fw_devlink misc fixes

On Wed, 2020-04-15 at 11:17 -0700, Saravana Kannan wrote:
> On Wed, Apr 15, 2020 at 8:06 AM Nicolas Saenz Julienne
> <nsaenzjulienne@...e.de> wrote:
> > As I'm interested in using this feature to fine-tune Raspberry Pi 4's
> 
> You've made my day! Finally another user outside of Android. :) If
> this does improve the boot time, I'd be super interested to see the
> numbers.

Actually making the boot time faster isn't my main objective just a nice
possible side-effect. I'll give you some numbers nonetheless :).

I have two things in mind:
 - Exploring if fw_devlink=on can help us solve a rather convoluted device
   initialization depency we're seeing in RPi4. It could potentially prevent us
   from adding nasty platform specific driver code.
 - See if we can use all this information to fine-tune initrd generation on
   smaller arm devices with limited i/o speeds.

Do you have any plans in moving the default behavior to fw_devlink=on? If so
what is blocking us?

Also do you think it'd be reasonable to add a DT binding to set the desired
fw_devlink level? Something like a 'linux,fw_devlink' property under the
/chosen node.

> > device probe dependencies, I tried to get the board to boot with
> > fw_devlink=on. As of today's linux-next the board won't boot with that
> > option. I tried to address the underlying issues.
> 
> I'll review the patches. Apologies in advance if my explanations
> aren't thorough. A bit swamped right now.

They were pretty clear!

Thanks,
Nicolas


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