linux-kernel - Re: [PATCH] usb: mtk-xhci: Set the XHCI_NO_64BIT

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Message-ID: <CAAFQd5AszvSow2vgRq+CbtBzdNO7ysymXp=xerR6dtmi8OxMZw@mail.gmail.com>
Date:   Fri, 11 Oct 2019 13:35:48 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     linux-usb@...r.kernel.org, Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Changqi Hu <Changqi.Hu@...iatek.com>,
        Nicolas Boichat <drinkcat@...omium.org>,
        Shik Chen <shik@...omium.org>
Subject: Re: [PATCH] usb: mtk-xhci: Set the XHCI_NO_64BIT_SUPPORT quirk

On Thu, Oct 10, 2019 at 7:59 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
>
> On Thu, 2019-10-10 at 18:00 +0900, Tomasz Figa wrote:
> > Hi Chunfeng,
> >
> > On Thu, Oct 10, 2019 at 5:45 PM Chunfeng Yun <chunfeng.yun@...iatek.com> wrote:
> > >
> > > Hi, Tomasz,
> > >
> > > On Thu, 2019-10-10 at 16:50 +0900, Tomasz Figa wrote:
> > > > MediaTek XHCI host controller does not support 64-bit addressing despite
> > > > the AC64 bit of HCCPARAMS1 register being set. The platform-specific
> > > > glue sets the DMA mask to 32 bits on its own, but it has no effect,
> > > > because xhci_gen_setup() overrides it according to hardware
> > > > capabilities.
> Yes, this is what I want to do, maybe need remove DMA mask setting in
> platform-specific.
>
> > > >
> > > > Use the XHCI_NO_64BIT_SUPPORT quirk to tell the XHCI core to force
> > > > 32-bit DMA mask instead.
> > > >
> > > > Signed-off-by: Tomasz Figa <tfiga@...omium.org>
> > > > ---
> > > >  drivers/usb/host/xhci-mtk.c | 10 +++++-----
> > > >  1 file changed, 5 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> > > > index b18a6baef204a..4d101d52cc11b 100644
> > > > --- a/drivers/usb/host/xhci-mtk.c
> > > > +++ b/drivers/usb/host/xhci-mtk.c
> > > > @@ -395,6 +395,11 @@ static void xhci_mtk_quirks(struct device *dev, struct xhci_hcd *xhci)
> > > >       xhci->quirks |= XHCI_SPURIOUS_SUCCESS;
> > > >       if (mtk->lpm_support)
> > > >               xhci->quirks |= XHCI_LPM_SUPPORT;
> > > > +     /*
> > > > +      * MTK host controller does not support 64-bit addressing, despite
> > > > +      * having the AC64 bit of the HCCPARAMS1 register set.
> > > > +      */
> > > > +     xhci->quirks |= XHCI_NO_64BIT_SUPPORT;
> > > Somes SoCs support 64bits in fact, so can't support this quirk, do you
> > > encounter any issues without this quirk?
> > >
> >
> > Thanks for taking a look at this patch.
> >
> > Yes, on MT8183 the DMA mask ended up being set to 64 bits, but
> > according to the information I received from MediaTek, the controller
> > on that SoC only supports 32 bits.
> As I know, mt8183 doesn't support memory greater than 4G mode.
>

We have 4GB of DRAM at 0x40000000-0x140000000 on our board with
MT8183. What happens if you attempt to use the memory from
0x100000000-0x140000000 with the XHCI controller on this SoC?

> >
> > If some SoCs support only 32 bits and some support 64 bits, we may
> > either need to use different DT compatible string for them or add a DT
> > property and set the quirk based on that. Right now in upstream we
> > have:
> >
> > 1) "mediatek,mt8173-xhci", used by:
> > MT8173
> >
> > 2)"mediatek,mtk-xhci", used by:
> > MT2712
> > MT7622
> > MT8183 (not yet upstream, but I suppose it's on the mailing lists)
> >
> > Would you be able to check which of the SoCs above report 64 bits but
> > support only 32? (and so would need this quirk)
> I'm afraid I can't, almost all MTK SoCs supporting xHCI are using this
> driver, AC64 should be set rightly according to addressing capability.
>

Does it mean that only MT8183 may be the only SoC with a problem with
this capability bit?

Matthias, do you have access to MT2712 and MT7622 devices? I have
MT8173 and MT8183, so I can check them, but would be good to check
this on the other ones too.

Best regards,
Tomasz