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

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Date:   Thu, 10 Oct 2019 16:45:18 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Tomasz Figa <tfiga@...omium.org>
CC:     <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        "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

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.
> 
> 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?

>  }

>  
>  /* 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;