Re: [PATCH 2/3] usb: xhci-mtk: fix UAS issue by XHCI_BROKEN_STREAMS quirk

[Nicolas Boichat <drinkcat@chromium.org>]

On Thu, Dec 17, 2020 at 10:19 AM Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
>
> On Wed, 2020-12-16 at 20:28 +0800, Nicolas Boichat wrote:
> > On Wed, Dec 16, 2020 at 7:53 PM Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
> > >
> > > The 0.96 xHCI controller on some platforms does not support
> > > bulk stream even HCCPARAMS says supporting, due to MaxPSASize
> > > is set a non-zero default value by mistake, here use
> > > XHCI_BROKEN_STREAMS quirk to fix it.
> > >
> > > Fixes: 94a631d91ad3 ("usb: xhci-mtk: check hcc_params after adding primary hcd")
> > > Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> > > ---
> > >  drivers/usb/host/xhci-mtk.c | 7 ++++++-
> > >  drivers/usb/host/xhci-mtk.h | 1 +
> > >  2 files changed, 7 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
> > > index 8f321f39ab96..08dab974d847 100644
> > > --- a/drivers/usb/host/xhci-mtk.c
> > > +++ b/drivers/usb/host/xhci-mtk.c
> > > @@ -395,6 +395,9 @@ 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;
> > > +
> > > +       if (mtk->broken_streams)
> > > +               xhci->quirks |= XHCI_BROKEN_STREAMS;
> > >  }
> > >
> > >  /* called during probe() after chip reset completes */
> > > @@ -460,6 +463,8 @@ static int xhci_mtk_probe(struct platform_device *pdev)
> > >                 return ret;
> > >
> > >         mtk->lpm_support = of_property_read_bool(node, "usb3-lpm-capable");
> > > +       mtk->broken_streams =
> > > +               of_property_read_bool(node, "mediatek,broken_streams_quirk");
> >
> > Would it be better to add a data field to struct of_device_id
> > mtk_xhci_of_match, and enable this quirk on mediatek,mt8173-xhci only?
> This is the common issue for all SoCs (before 2016.06) with 0.96 xHCI
> when the controller don't support bulk stream. If enable this quirk only
> for mt8173, then for other SoCs, the compatible need include
> "mediatek,mt8173-xhci" in dts, this may be not flexible for some cases,
> e.g. a new SoC has the broken stream as mt8173, but also has another
> different quirk, the way you suggested will not handle it.

It can, we do this regularly for many other components. One example:
https://elixir.bootlin.com/linux/latest/source/drivers/i2c/busses/i2c-mt65xx.c#L402

> And I plan to remove "mediatek,mt8173-xhci" in mtk_xhci_of_match after
> converting the binding to YMAL.
>
> >
> > (IMHO usb3-lpm-capable detection should also be done in the same way)
> I prefer to provide a property for common issues, and use the way you
> suggested for the issue only happened at a specific SoC.

Understand, it's just different approaches, there seems to be
precedent (at least in this driver/binding) for using properties, so
I'll let the USB maintainers speak up ,-)

>
> Thank you
>
> >
> > Thanks,
> >
> > >         /* optional property, ignore the error if it does not exist */
> > >         of_property_read_u32(node, "mediatek,u3p-dis-msk",
> > >                              &mtk->u3p_dis_msk);
> > > @@ -546,7 +551,7 @@ static int xhci_mtk_probe(struct platform_device *pdev)
> > >         if (ret)
> > >                 goto put_usb3_hcd;
> > >
> > > -       if (HCC_MAX_PSA(xhci->hcc_params) >= 4)
> > > +       if (!mtk->broken_streams && HCC_MAX_PSA(xhci->hcc_params) >= 4)
> > >                 xhci->shared_hcd->can_do_streams = 1;
> > >
> > >         ret = usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
> > > diff --git a/drivers/usb/host/xhci-mtk.h b/drivers/usb/host/xhci-mtk.h
> > > index a93cfe817904..86aa4978915e 100644
> > > --- a/drivers/usb/host/xhci-mtk.h
> > > +++ b/drivers/usb/host/xhci-mtk.h
> > > @@ -147,6 +147,7 @@ struct xhci_hcd_mtk {
> > >         struct phy **phys;
> > >         int num_phys;
> > >         bool lpm_support;
> > > +       bool broken_streams;
> > >         /* usb remote wakeup */
> > >         bool uwk_en;
> > >         struct regmap *uwk;
> > > --
> > > 2.18.0
>