Message-ID: <319cb654-51f6-6241-802b-22ee0d5b0aab@linaro.org>
Date:   Thu, 23 Feb 2023 10:12:29 +0100
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Subject: Re: [PATCH v1 RFC 1/3] dt-bindings: serial: amlogic,meson-uart: Add
 compatible string for G12A
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To:     Martin Blumenstingl <martin.blumenstingl@googlemail.com>,
        linux-amlogic@lists.infradead.org, devicetree@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        jirislaby@kernel.org, neil.armstrong@linaro.org,
        krzysztof.kozlowski+dt@linaro.org, robh+dt@kernel.org,
        gregkh@linuxfoundation.org,
        Christian Hewitt <christianshewitt@gmail.com>
References: <20230222210425.626474-1-martin.blumenstingl@googlemail.com>
 <20230222210425.626474-2-martin.blumenstingl@googlemail.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <20230222210425.626474-2-martin.blumenstingl@googlemail.com>
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On 22/02/2023 22:04, Martin Blumenstingl wrote:
> Amlogic G12A SoCs gained a new "divide XTAL by 2" bit. Everything else
> (we know about) is identical to the UART IP on GX (GXBB/GXL/GXM) SoCs.
> Add a new compatible string for this SoC so this new bit can be managed
> accordingly.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
> ---
> Why am I sending this as RFC? The last change in this series means
> that the resulting .dtbs are not compatible with old kernels anymore.
> My understanding is that this is fine and only the opposite case (using
> old .dtbs on new kernels) has to be supported (which is still the case
> with this series). I'd like to get some confirmation for this.

The other way around is also nice to have, because DTS is used in other
projects. You fixed here Linux kernel, but what about all other
out-of-tree kernels, BSDs, firmwares and bootloaders? Did you fix them
as well?

The question is whether the devices can be made compatible thus keeping
DTS working on older kernel. This commit suggests they are. Your DTS
commit is written in different tone - something was broken and is being
fixed.

Best regards,
Krzysztof