linux-kernel - Re: [PATCH v3 2/9] reset: Add Raspberry Pi 4 firmware reset controller

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Message-ID: <6ddaf69d4f5ad188864f62dcdbfbbe32acef9820.camel@pengutronix.de>
Date:   Fri, 26 Jun 2020 12:43:07 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        f.fainelli@...il.com, gregkh@...uxfoundation.org, wahrenst@....net,
        linux-kernel@...r.kernel.org
Cc:     linux-usb@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com, tim.gover@...pberrypi.org,
        linux-pci@...r.kernel.org, helgaas@...nel.org,
        andy.shevchenko@...il.com, mathias.nyman@...ux.intel.com,
        lorenzo.pieralisi@....com
Subject: Re: [PATCH v3 2/9] reset: Add Raspberry Pi 4 firmware reset
 controller

On Wed, 2020-06-17 at 12:44 +0200, Nicolas Saenz Julienne wrote:
> On Wed, 2020-06-17 at 12:02 +0200, Philipp Zabel wrote:
> > Hi Nicolas,
> > 
> > On Fri, 2020-06-12 at 19:13 +0200, Nicolas Saenz Julienne wrote:
> > > Raspberry Pi 4's co-processor controls some of the board's HW
> > > initialization process, but it's up to Linux to trigger it when
> > > relevant. Introduce a reset controller capable of interfacing with
> > > RPi4's co-processor that models these firmware initialization routines as
> > > reset lines.
> > > 
> > > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> > > Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> > 
> > Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>
> 
> Thanks!
> 
> > If there is a good reason for the single DT specified reset id, I can
> > pick up patches 1 and 2.
> 
> The idea here is to make sure we're reasonably covered against further changes
> in firmware. If we define constraints too narrow it can be a pain to support
> new features without breaking backwards compatibility in dt.

Ok.

> > If you change the dts patch 4 to use a number instead of the reset id
> > define for now, there wouldn't even be a dependency between these reset
> > and dts patches.
> 
> I was under the impression that having an explicit definition was nice to have.
> What's troubling about creating the dependency?

Just that the last patch has to wait for the reset patches to be merged
before it can be applied.

regards
Philipp