From: Rob Herring <robh@kernel.org>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Alessandro Zummo <a.zummo@towertech.it>,
Alexandre Belloni <alexandre.belloni@bootlin.com>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
linux-rtc@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
od@opendingux.net
Subject: Re: [PATCH v2 1/4] dt-bindings: rtc: ingenic: Rework compatible strings and add #clock-cells
Date: Tue, 1 Nov 2022 12:32:05 -0500 [thread overview]
Message-ID: <CAL_JsqLOdnm8XNrEbeVtQeq4qtTyqUs_uGyhwzmUKha43ijTuw@mail.gmail.com> (raw)
In-Reply-To: <WNUMKR.BWKAZLU4SGE52@crapouillou.net>
On Mon, Oct 31, 2022 at 2:41 PM Paul Cercueil <paul@crapouillou.net> wrote:
>
> Hi Rob,
>
> Le lun. 31 oct. 2022 à 14:23:41 -0500, Rob Herring <robh@kernel.org> a
> écrit :
> > On Fri, Oct 28, 2022 at 11:55:16PM +0100, Paul Cercueil wrote:
> >> The RTC in the JZ4770 is compatible with the JZ4760, but has an
> >> extra
> >> register that permits to configure the behaviour of the CLK32K pin.
> >> The
> >> same goes for the RTC in the JZ4780.
> >>
> >> Therefore, the ingenic,jz4770-rtc and ingenic,jz4780-rtc strings do
> >> not
> >> fall back anymore to ingenic,jz4760-rtc. The ingenic,jz4780-rtc
> >> string
> >> now falls back to the ingenic,jz4770-rtc string.
> >
> > This is a compatibility mess. There is no driver support in v6.1-rc
> > for
> > ingenic,jz4770-rtc, so a new DT would not work with existing kernels.
> > It
> > sounds like you need 3 compatibles for 4780.
>
> Do newer DTs need to work with older kernels? I always assumed the
> compatibility was only enforced for the other way around.
For a stable platform, yes. Would you want a firmware update carrying
the DT to break an existing OS install?
Compatibility either way ultimately is up to the platform whether you
care or not. I just ask that the commit msg spell that out. In this
case, it is easily avoided.
Rob
next prev parent reply other threads:[~2022-11-01 17:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-28 22:55 [PATCH v2 0/4] rtc: ingenic: various updates Paul Cercueil
2022-10-28 22:55 ` [PATCH v2 1/4] dt-bindings: rtc: ingenic: Rework compatible strings and add #clock-cells Paul Cercueil
2022-10-31 19:23 ` Rob Herring
2022-10-31 19:40 ` Paul Cercueil
2022-11-01 17:32 ` Rob Herring [this message]
2022-10-28 22:55 ` [PATCH v2 2/4] rtc: jz4740: Use readl_poll_timeout Paul Cercueil
2022-10-28 22:55 ` [PATCH v2 3/4] rtc: jz4740: Register clock provider for the CLK32K pin Paul Cercueil
2022-10-28 22:55 ` [PATCH v2 4/4] rtc: jz4740: Support for fine-tuning the RTC clock Paul Cercueil
2022-10-29 8:51 ` kernel test robot
2022-10-29 11:52 ` Paul Cercueil
2022-11-02 17:40 ` [PATCH v2 0/4] rtc: ingenic: various updates Alexandre Belloni
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