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From: Matthias Brugger <matthias.bgg@gmail.com>
To: Chen-Yu Tsai <wenst@chromium.org>,
	Jianjun Wang <jianjun.wang@mediatek.com>
Cc: Ryder Lee <ryder.lee@mediatek.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Rob Herring <robh+dt@kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Randy Wu <Randy.Wu@mediatek.com>,
	youlin.pei@mediatek.com
Subject: Re: [PATCH 1/2] dt-bindings: PCI: mediatek-gen3: Add support for MT8195
Date: Wed, 2 Jun 2021 13:33:07 +0200	[thread overview]
Message-ID: <db62910b-febd-6cba-8a72-2bf718f7b110@gmail.com> (raw)
In-Reply-To: <CAGXv+5GMTbC5TTgURhPAvxBEY18S6-T-BZ9CpXsO91Trim7TXw@mail.gmail.com>



On 01/06/2021 08:07, Chen-Yu Tsai wrote:
> Hi,
> 
> On Tue, Jun 1, 2021 at 1:50 PM Jianjun Wang <jianjun.wang@mediatek.com> wrote:
>>
>> On Tue, 2021-06-01 at 11:53 +0800, Chen-Yu Tsai wrote:
>>> Hi,
>>>
>>> On Tue, Jun 1, 2021 at 10:50 AM Jianjun Wang <jianjun.wang@mediatek.com> wrote:
>>>>
>>>> MT8195 is an ARM platform SoC which has the same PCIe IP with MT8192.
>>>
>>> Based on what I'm seeing internally, there seems to be some inconsistency
>>> across the MediaTek platform on whether new compatible strings should be
>>> introduced for "fully compatible" IP blocks.
>>>
>>> If this hardware block in MT8195 is "the same" as the one in MT8192, do we
>>> really need the new compatible string? Are there any concerns?
>>
>> Hi Chen-Yu,
>>
>> It's ok to reuse the compatible string with MT8192, but I think this
>> will be easier to find which platforms this driver is compatible with,
>> especially when we have more and more platforms in the future.
> 
> If it's just for informational purposes, then having the MT8192 compatible
> as a fallback would work, and we wouldn't need to make changes to the driver.
> This works better especially if we have to support multiple operating systems
> that use device tree.
> 
> So we would want
> 
>     "mediatek,mt8195-pcie", "mediatek,mt8192-pcie"
> 
> and
> 
>     "mediatek,mt8192-pcie"
> 
> be the valid options.
> 
> Personally I'm not seeing enough value to justify adding the compatible string
> just for informational purposes though. One could easily discern which hardware
> is used by looking at the device tree.
> 

I agree, if no differences between the two chips are known, adding a binding
withe new compatible and a fallback is a good thing. If we later on realize that
mt8195 PCI block has differences, we can add the matching to the driver.

Regards,
Matthias

> 
> Regards
> ChenYu
> 
> 
>> Thanks.
>>>
>>>
>>> Thanks
>>> ChenYu
>>>
>>>
>>>> Signed-off-by: Jianjun Wang <jianjun.wang@mediatek.com>
>>>> ---
>>>>  Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml | 4 +++-
>>>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml b/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
>>>> index e7b1f9892da4..d5e4a3e63d97 100644
>>>> --- a/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
>>>> +++ b/Documentation/devicetree/bindings/pci/mediatek-pcie-gen3.yaml
>>>> @@ -48,7 +48,9 @@ allOf:
>>>>
>>>>  properties:
>>>>    compatible:
>>>> -    const: mediatek,mt8192-pcie
>>>> +    oneOf:
>>>> +      - const: mediatek,mt8192-pcie
>>>> +      - const: mediatek,mt8195-pcie
>>>>
>>>>    reg:
>>>>      maxItems: 1
>>>> --
>>>> 2.18.0
>>>> _______________________________________________
>>>> Linux-mediatek mailing list
>>>> Linux-mediatek@lists.infradead.org
>>>> http://lists.infradead.org/mailman/listinfo/linux-mediatek
>>

  reply	other threads:[~2021-06-02 11:33 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-01  2:44 [PATCH 0/2] PCI: mediatek-gen3: Add controller support for MT8195 Jianjun Wang
2021-06-01  2:44 ` [PATCH 1/2] dt-bindings: PCI: mediatek-gen3: Add " Jianjun Wang
2021-06-01  3:53   ` Chen-Yu Tsai
2021-06-01  5:49     ` Jianjun Wang
2021-06-01  6:07       ` Chen-Yu Tsai
2021-06-02 11:33         ` Matthias Brugger [this message]
2021-06-22 11:05           ` Lorenzo Pieralisi
2021-06-23  9:02             ` Jianjun Wang
2021-06-01  2:44 ` [PATCH 2/2] PCI: mediatek-gen3: Add controller " Jianjun Wang

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