Re: [PATCH v3 2/4] arm64: dts: correct vendor prefix hisi to hisilicon

From: Wei Xu <xuwei5@hisilicon.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: devicetree <devicetree@vger.kernel.org>,
	Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
	Chen Feng <puck.chen@hisilicon.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Zhen Lei <thunder.leizhen@huawei.com>,
	Zhangfei Gao <zhangfei.gao@linaro.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3 2/4] arm64: dts: correct vendor prefix hisi to hisilicon
Date: Fri, 29 Jan 2021 16:27:58 +0800	[thread overview]
Message-ID: <6013C70E.7050100@hisilicon.com> (raw)
In-Reply-To: <CAK8P3a2xU+LXnyQN5pU5+pwWDUUwqpPVN2hhWKPvExWKw5F=wQ@mail.gmail.com>

Hi Arnd,

On 2021/1/29 16:21, Arnd Bergmann wrote:
> On Fri, Jan 29, 2021 at 2:57 AM Wei Xu <xuwei5@hisilicon.com> wrote:
>> On 2021/1/29 9:02, Wei Xu wrote:
>>> On 2021/1/28 22:08, Arnd Bergmann wrote:
>>>> 2. Updating the dtb while running an older kernel is now broken since
>>>>   the driver can no longer read the property. This is less critical, but
>>>>   it does seem easy enough to work around here by leaving both
>>>>   properties in place.
>>>
>>> Yes, it is.
>>> But if leaving both in place, the dtbs_check will report following warning again:
>>>       'hisi,rst-syscon' does not match any of the regexes
>>>
>>> That is why leizhen changed the dtb.
>>> Do you think it is OK to assume no one will use the new dtb with an older kernel?
>>>
>>>>
>>>> 3. Bisecting through the git history across an incompatible change
>>>>   means you can run into broken commits. We try hard to avoid that
>>>>   if we are aware of a problem in advance. In this case it could be
>>>>   avoided by only merging the incompatible DT change in a following
>>>>   merge window after the driver change, or (better) by making it
>>>>   a backward-compatible change the same way as addressing 2.
>>>
>>> Yes, agreed.
>>> And The DT change pull request is sent after the driver has been merged into v5.11-rc1.
>>
>> I can drop this patch and revert what I have changed in Mauro's following patch:
>>         "arm64: dts: hisilicon: hi3670.dtsi: add iomcu_rst"
>>
>> Then resend the pull request. And pick up this patch after the next merge window.
>> Do you think is it OK?
> 
> Let's start with the updated pull request without this patch so I can merge
> the other changes you sent.

Got it. Thanks!

> 
> I'm still not convinced it helps to drop the property rather than having
> both. I think it should be possible to list the old property name in the
> binding as 'deprecated' and keep it in the .dts for backwards compatibility
> but leave it out in future dts files. Maybe move it into the board .dts file(s)
> and make the .dtsi file have only the new property.

Thanks!
I will check with Lei Zhen to see which is possible.

Best Regards,
Wei

> 
>       Arnd
> .
> 

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