Re: [PATCH] usb: mtk-xhci: Set the XHCI_NO_64BIT_SUPPORT quirk

From: Nicolas Boichat <drinkcat@chromium.org>
To: Tomasz Figa <tfiga@chromium.org>
Cc: linux-usb@vger.kernel.org,
	Mathias Nyman <mathias.nyman@intel.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-arm-kernel@lists.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>,
	open list <linux-kernel@vger.kernel.org>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	Changqi Hu <Changqi.Hu@mediatek.com>,
	Shik Chen <shik@chromium.org>
Subject: Re: [PATCH] usb: mtk-xhci: Set the XHCI_NO_64BIT_SUPPORT quirk
Date: Thu, 10 Oct 2019 17:07:58 +0800	[thread overview]
Message-ID: <CANMq1KAA+nqcOqiE_g=vA8DC=_t=FqSRtR5kk=1XqSsgZGj+_A@mail.gmail.com> (raw)
In-Reply-To: <20191010075004.192818-1-tfiga@chromium.org>

On Thu, Oct 10, 2019 at 3:50 PM Tomasz Figa <tfiga@chromium.org> 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.
>
> 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@chromium.org>

Can we add a Fixes: tag for stable backports?
(after addressing the other comments of course)

> ---
>  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;
>  }
>
>  /* called during probe() after chip reset completes */
> @@ -488,11 +493,6 @@ static int xhci_mtk_probe(struct platform_device *pdev)
>                 goto disable_clk;
>         }
>
> -       /* Initialize dma_mask and coherent_dma_mask to 32-bits */
> -       ret = dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
> -       if (ret)
> -               goto disable_clk;
> -
>         hcd = usb_create_hcd(driver, dev, dev_name(dev));
>         if (!hcd) {
>                 ret = -ENOMEM;
> --
> 2.23.0.581.g78d2f28ef7-goog
>