linux-kernel - Re: [PATCH] arm64: dts: mediatek: mt8195: Add missing clock for xhci1 controller

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Message-ID: <CAGXv+5G92=-k5MDH4BPcM8tgPwcGTJ60trJwr7BwTGHD=wpnDw@mail.gmail.com>
Date: Fri, 26 Jul 2024 23:11:37 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Nícolas F. R. A. Prado <nfraprado@...labora.com>, 
	Matthias Brugger <matthias.bgg@...il.com>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, kernel@...labora.com, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] arm64: dts: mediatek: mt8195: Add missing clock for xhci1 controller

On Fri, Jul 26, 2024 at 8:11 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com> wrote:
>
> Il 25/07/24 12:34, Chen-Yu Tsai ha scritto:
> > Hi,
> >
> > On Mon, Jul 22, 2024 at 11:27 PM Nícolas F. R. A. Prado
> > <nfraprado@...labora.com> wrote:
> >>
> >> Currently if the xhci1 controller happens to probe before the pcie1
> >> controller then it fails with the following errors:
> >>
> >> xhci-mtk 11290000.usb: clocks are not stable (0x1003d0f)
> >> xhci-mtk 11290000.usb: can't setup: -110
> >> xhci-mtk: probe of 11290000.usb failed with error -110
> >>
> >> The issue has been tracked down to the CLK_INFRA_AO_PCIE_P1_TL_96M
> >> clock, although exactly why this pcie clock is needed for the usb
> >> controller is still unknown. Add the clock to the xhci1 controller so it
> >> always probes successfully and use a placeholder clock name for it.
> >>
> >> Reported-by: Nícolas F. R. A. Prado <nfraprado@...labora.com> #KernelCI
> >> Closes: https://lore.kernel.org/all/9fce9838-ef87-4d1b-b3df-63e1ddb0ec51@notapiano/
> >> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> >
> > So I asked MediaTek about this, and it seems the correct thing to do is
> > disable USB 3 on this host controller using the following snippet. The
> > snippet is copy-pasted from our issue tracker and won't apply directly.
> >
> > This is also seen in mt8395-kontron-3-5-sbc-i1200.dts, on which xhci1
> > is used only for USB 2.0 on an M.2 slot.
> >
>
> Uhm, okay, but why should USB3 be disabled on a controller that supports USB3?
>
> I agree about disabling it on specific boards that use only the USB 2.0 lines of
> this controller, but doing that globally looks wrong... and looks like being a
> workaround for an error that gets solved with adding a clock as well.
>
> In short, the question is: why would that be the correct thing to do?

We can disable it in mt8195-cherry.dtsi then?

ChenYu

> Cheers,
> Angelo
>
> >
> > ChenYu
> >
> > index 8b7307cdefc6..2dac9f706a58
> > --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> > +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> > @@ -1447,6 +1447,7 @@
> >                                        "xhci_ck";
> >                          mediatek,syscon-wakeup = <&pericfg 0x400 104>;
> >                          wakeup-source;
> > +                       mediatek,u3p-dis-msk = <0x1>;
> >                          status = "disabled";
> >                  };
> >
> >> ---
> >>   arch/arm64/boot/dts/mediatek/mt8195.dtsi | 10 ++++++++--
> >>   1 file changed, 8 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> >> index 2ee45752583c..cc5169871f1c 100644
> >> --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> >> +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
> >> @@ -1453,9 +1453,15 @@ xhci1: usb@...90000 {
> >>                                   <&topckgen CLK_TOP_SSUSB_P1_REF>,
> >>                                   <&apmixedsys CLK_APMIXED_USB1PLL>,
> >>                                   <&clk26m>,
> >> -                                <&pericfg_ao CLK_PERI_AO_SSUSB_1P_XHCI>;
> >> +                                <&pericfg_ao CLK_PERI_AO_SSUSB_1P_XHCI>,
> >> +                                /*
> >> +                                 * This clock is required due to a hardware
> >> +                                 * bug. The 'frmcnt_ck' clock name is used as a
> >> +                                 * placeholder.
> >> +                                 */
> >> +                                <&infracfg_ao CLK_INFRA_AO_PCIE_P1_TL_96M>;
> >>                          clock-names = "sys_ck", "ref_ck", "mcu_ck", "dma_ck",
> >> -                                     "xhci_ck";
> >> +                                     "xhci_ck", "frmcnt_ck";
> >>                          mediatek,syscon-wakeup = <&pericfg 0x400 104>;
> >>                          wakeup-source;
> >>                          status = "disabled";
> >>
> >> ---
> >> base-commit: dee7f101b64219f512bb2f842227bd04c14efe30
> >> change-id: 20240722-usb-1129-probe-pci-clk-fix-ef8646f46aac
> >>
> >> Best regards,
> >> --
> >> Nícolas F. R. A. Prado <nfraprado@...labora.com>
> >>
> >>
>
>
>