linux-kernel - RE: [PATCH v2 5/5] dt-bindings: aspeed-lpc: Remove LPC partitioning

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Date:   Tue, 15 Dec 2020 02:17:34 +0000
From:   ChiaWei Wang <chiawei_wang@...eedtech.com>
To:     Andrew Jeffery <andrew@...id.au>, Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>
CC:     Ryan Chen <ryan_chen@...eedtech.com>,
        Lee Jones <lee.jones@...aro.org>,
        Corey Minyard <minyard@....org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Haiyue Wang <haiyue.wang@...ux.intel.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "openbmc@...ts.ozlabs.org" <openbmc@...ts.ozlabs.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: RE: [PATCH v2 5/5] dt-bindings: aspeed-lpc: Remove LPC partitioning

Hi Andrew,

> -----Original Message-----
> From: Andrew Jeffery <andrew@...id.au>
> Sent: Tuesday, December 15, 2020 8:12 AM
> To: ChiaWei Wang <chiawei_wang@...eedtech.com>; Rob Herring
> <robh+dt@...nel.org>; Joel Stanley <joel@....id.au>
> Cc: Ryan Chen <ryan_chen@...eedtech.com>; Lee Jones
> <lee.jones@...aro.org>; Corey Minyard <minyard@....org>; Arnd Bergmann
> <arnd@...db.de>; Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Linus
> Walleij <linus.walleij@...aro.org>; Haiyue Wang
> <haiyue.wang@...ux.intel.com>; linux-arm-kernel@...ts.infradead.org;
> linux-aspeed@...ts.ozlabs.org; linux-kernel@...r.kernel.org;
> openbmc@...ts.ozlabs.org; linux-gpio@...r.kernel.org
> Subject: Re: [PATCH v2 5/5] dt-bindings: aspeed-lpc: Remove LPC partitioning
> 
> Hi Chiawei,
> 
> On Mon, 14 Dec 2020, at 13:14, ChiaWei Wang wrote:
> > Hi Andrew & Rob,
> >
> > Do you have any suggestion on this patch?
> 
> Rob hasn't responded, but I think it will be easier to get an Ack out of him if we
> do a v2 of the binding so we're not breaking backwards-compatibility with the
> current definition. Concretely:
> 
> - compatible:   One of:
>                 "aspeed,ast2400-lpc", "simple-mfd"
>                 "aspeed,ast2500-lpc", "simple-mfd"
> 
> Becomes something like:
> 
> - compatible:   One of:
>                 "aspeed,ast2400-lpc-v2", "simple-mfd"
>                 "aspeed,ast2500-lpc-v2", "simple-mfd"
> 
> We can convert the in-tree devicetrees, immediately drop support for the
> current binding in the drivers, and _only_ support v2 of the binding going
> forward. That way your patches stay largely the same, the binding isn't
> hamstrung as it is currently, and we're not trying to maintain code to support
> the current binding definition - but we're also not pretending that old
> devicetrees will work with newer kernels that only support the new binding
> definition (which is the problem with your current patch series).
> 
> How does that sound?
Sounds good. The v2 binding string should be a notification to sync both the new device tree and the new drivers.
I will prepare a v3 patch with this change and the commit reordering suggested.

Thanks,
Chiawei

> 
> As to how to implement this, I think we'll need to add some
> of_device_is_compatible() checks in the relevant drivers to make sure that
> they're using the new LPC binding, such as in
> drivers/pinctrl/aspeed/pinctrl-aspeed-g5.c before we fetch the regmap on line
> 2657.
> 
> Sorry that this is dragging out a bit (and for the mess I made).
> 
> Cheers,
> 
> Andrew