linux-kernel - Re: [PATCH v3 3/3] PCI: apple: Fix #PERST polarity

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Date:   Wed, 24 Nov 2021 10:16:10 +0100
From:   Luca Ceresoli <luca@...aceresoli.net>
To:     Marc Zyngier <maz@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pci@...r.kernel.org,
        Pali Rohár <pali@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        kernel-team@...roid.com
Subject: Re: [PATCH v3 3/3] PCI: apple: Fix #PERST polarity

Hi,

On 24/11/21 10:02, Marc Zyngier wrote:
> On Tue, 23 Nov 2021 21:36:11 +0000,
> Luca Ceresoli <luca@...aceresoli.net> wrote:
>>
>> Hi Mark,
>>
>> On 23/11/21 19:06, Marc Zyngier wrote:
>>> Now that #PERST is properly defined as active-low in the device tree,
>>> fix the driver to correctly drive the line indemendently of the
>>> implied polarity.
>>>
>>> Fixes: 1e33888fbe44 ("PCI: apple: Add initial hardware bring-up")
>>> Suggested-by: Pali Rohár <pali@...nel.org>
>>> Signed-off-by: Marc Zyngier <maz@...nel.org>
>>
>> Thanks for quickly addressing this!
>>
>> Do we need a transition path for backward compatibility with old DTs
>> already around? Something like this [0]. You said [1] the DT actually
>> used is not even the one in the kernel, thus how do we guarantee DT and
>> driver switch to the new polarity all at once?
> 
> No. As it turns out, neither u-boot nor OpenBSD (the only two other
> payloads that can boot on M1) are upstreamed yet. So we're still in
> that stage where we don't need to maintain backward compatibility. If
> we don't get this patches merged by the end of this cycle, we will
> have to revisit this though.

Good news!

Reviewed-by: Luca Ceresoli <luca@...aceresoli.net>

-- 
Luca