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Wed, 02 Jun 2021 04:33:09 -0700 (PDT) Subject: Re: [PATCH 1/2] dt-bindings: PCI: mediatek-gen3: Add support for MT8195 To: Chen-Yu Tsai , Jianjun Wang Cc: Ryder Lee , Bjorn Helgaas , Rob Herring , Lorenzo Pieralisi , 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 , youlin.pei@mediatek.com References: <20210601024408.24485-1-jianjun.wang@mediatek.com> <20210601024408.24485-2-jianjun.wang@mediatek.com> <1622526594.9054.6.camel@mhfsdcap03> From: Matthias Brugger Message-ID: Date: Wed, 2 Jun 2021 13:33:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210602_043312_615294_0C909B39 X-CRM114-Status: GOOD ( 33.00 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 01/06/2021 08:07, Chen-Yu Tsai wrote: > Hi, > > On Tue, Jun 1, 2021 at 1:50 PM Jianjun Wang 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 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 >>>> --- >>>> 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 >> _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel