linux-kernel - Re: [PATCH 0/6] Expose RPi4'd bootloader configuration

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Message-ID: <0c29dbdb8c6b042dd1c2dd6f4ed3b113aba19d97.camel@suse.de>
Date:   Tue, 15 Dec 2020 22:21:59 +0100
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Rob Herring <robh+dt@...nel.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        devicetree@...r.kernel.org,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "moderated list:BROADCOM BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will@...nel.org>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>
Subject: Re: [PATCH 0/6] Expose RPi4'd bootloader configuration

Hi Rob, thanks for having a look at this.

On Tue, 2020-12-15 at 13:54 -0600, Rob Herring wrote:
> On Tue, Dec 15, 2020 at 1:01 PM Nicolas Saenz Julienne
> <nsaenzjulienne@...e.de> wrote:
> > 
> > Hi Catalin,
> > 
> > On Tue, 2020-12-15 at 18:44 +0000, Catalin Marinas wrote:
> > > On Tue, Dec 15, 2020 at 04:56:20PM +0100, Nicolas Saenz Julienne wrote:
> > > > Soon to be released versions of RPi4's firmware will take of care
> > > > passing their bootloader's configuration to the OS by copying it into
> > > > memory and creating a reserved memory node in the board's DT. In order
> > > > to make use of this information, this series introduces a new generic
> > > > nvmem driver that maps reserved-memory nodes into nvmem devices.
> > > > 
> > > > An alternative approach, less nice IMO, would be to create a
> > > > platform-specific 'soc' driver.
> > > 
> > > What kind of information is this and how would the kernel use it?
> > 
> > Sorry, I wasn't clear enough, the ultimate goal is to use this information from
> > user-space, through nvmem's sysfs interface. The kernel itself has no use for
> > it.
> 
> That still leaves the first question.

It's the bootloader configuration, stuff like boot order, TFTP IP, etc... See
more here:
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711_bootloader_config.md

I'll add a new paragraph explaining all this on next version's cover letter.

Regards,
Nicolas


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