linux-kernel - Re: [PATCH 03/11] dt-bindings: usb: mtk-xhci: add compatible for mt8195

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Message-ID: <8166fa917d6df5002617c5fb5d614e5ff5bd6af6.camel@mediatek.com>
Date:   Thu, 19 Aug 2021 11:36:01 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mathias.nyman@...el.com" <mathias.nyman@...el.com>,
        Eddie Hung (洪正鑫) 
        <Eddie.Hung@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>
Subject: Re: [PATCH 03/11] dt-bindings: usb: mtk-xhci: add compatible for
 mt8195

On Wed, 2021-08-18 at 09:20 -0500, Rob Herring wrote:
> On Wed, Aug 11, 2021 at 3:02 AM Chunfeng Yun (云春峰)
> <Chunfeng.Yun@...iatek.com> wrote:
> > 
> > On Fri, 2021-08-06 at 14:43 -0600, Rob Herring wrote:
> > > On Fri, Jul 30, 2021 at 04:49:54PM +0800, Chunfeng Yun wrote:
> > > > There are 4 USB controllers on MT8195, the controllers
> > > > (IP1~IP3,
> > > > exclude IP0) have a wrong default SOF/ITP interval which is
> > > > calculated from the frame counter clock 24Mhz by default, but
> > > > in fact, the frame counter clock is 48Mhz, so we should set
> > > > the accurate interval according to 48Mhz. Here add a new
> > > > compatible
> > > > for MT8195, it's also supported in driver. But the first
> > > > controller
> > > > (IP0) has no such issue, we prefer to use generic compatible,
> > > > e.g. mt8192's compatible.
> > > 
> > > That only works until you find some 8195 bug common to all
> > > instances.
> > 
> > It's also OK for IP0 to use mt8195's compatible, these setting
> > value is
> > the same as IP0's default value, use mt8192's may avoid these dummy
> > setting.
> 
> I still don't understand. By use mt8192's compatible, that means you
> have for IP0:
> 
> compatible = "mediatek,mt8192-xhci", "mediatek,mtk-xhci";
> 
> And for the rest:
> compatible = "mediatek,mt8195-xhci", "mediatek,mtk-xhci";
No, use "mediatek,mt8195-xhci" is also ok for IP0.

Seems need modify commit log and remove last sentence to avoid
misunderstanding.

Thanks

> 
> If there's a 8195 quirk you need to work around, then you can't on
> IP0. You need to be able to address quirks in the future without
> changing the DTB. That is why we require SoC specific compatibles
> even
> when IP blocks are 'the same'.
> 
> Rob