linux-kernel - Re: [PATCH v3 8/9] dt-bindings: media: nxp,imx8mq-vpu: Update bindings

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Message-ID: <CAL_JsqJGZK2C8mcDiYa4yfKxf4sKykxSQ-Nfr4bi_u_OcAxW_Q@mail.gmail.com>
Date:   Tue, 23 Feb 2021 08:31:08 -0600
From:   Rob Herring <robh@...nel.org>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>
Cc:     Ezequiel Garcia <ezequiel@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Maxime Ripard <mripard@...nel.org>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Peng Fan <peng.fan@....com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        devicetree@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Collabora Kernel ML <kernel@...labora.com>
Subject: Re: [PATCH v3 8/9] dt-bindings: media: nxp,imx8mq-vpu: Update bindings

On Tue, Feb 23, 2021 at 2:04 AM Benjamin Gaignard
<benjamin.gaignard@...labora.com> wrote:
>
>
> Le 23/02/2021 à 01:34, Rob Herring a écrit :
> > On Mon, Feb 22, 2021 at 01:24:05PM +0100, Benjamin Gaignard wrote:
> >> The current bindings seem to make the assumption that the
> >> two VPUs hardware blocks (G1 and G2) are only one set of
> >> registers.
> >> After implementing the VPU reset driver and G2 decoder driver
> >> it shows that all the VPUs are independent and don't need to
> >> know about the registers of the other blocks.
> >> Remove from the bindings the need to set all blocks register
> >> but keep reg-names property because removing it from the driver
> >> may affect other variants.
> >>
> >> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...labora.com>
> >> ---
> >> version 2:
> >> - be more verbose about why I change the bindings
> >> Keep in mind that series comes after: https://www.spinics.net/lists/arm-kernel/msg875766.html
> >> without that review and ack it won't work
> > Better, but you've still mentioned nothing about breaking compatibility.
> > Why is that okay?
>
> Because this reg-names wasn't used before for this variant so remove it won't change anything.

It is the reset changes in the driver that break. The driver
previously got the 'ctrl' registers whether it went by name or index,
right? With an old DTB and a kernel with the changes (and vice-versa),
you'll have nothing to handle the VPU resets because the VPU reset
node doesn't exist. It could work if the default state is not held in
reset.

At least the removal of 'ctrl' registers belongs in the reset changes series.

Rob