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Date: Sun, 13 Sep 2026 14:53:24 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Haowen Bai <calvin.bai@ugreen.com>
Cc: mathias.nyman@intel.com, gregkh@linuxfoundation.org,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	stable@vger.kernel.org
Subject: Re: [PATCH] usb: pci-quirks: abort xHCI handoff if MMIO is
 inaccessible
Message-ID: <aqacxOz0jPWIfXGs@wunner.de>
References: <A8558181A93455E3+20260906162614.26940-1-calvin.bai@ugreen.com>
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In-Reply-To: <A8558181A93455E3+20260906162614.26940-1-calvin.bai@ugreen.com>

On Mon, Sep 07, 2026 at 12:26:14AM +0800, Haowen Bai wrote:
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -1026,15 +1026,22 @@ static void quirk_usb_disable_ehci(struct pci_dev *pdev)
>   * Returns 0 when the mask bits have the value done.
>   * Returns -ETIMEDOUT if this condition is not true after
>   * wait_usec microseconds have passed.
> + * Returns -ENODEV if the register reads as all-ones (hardware removed).
>   */
>  static int handshake(void __iomem *ptr, u32 mask, u32 done,
>  		int wait_usec, int delay_usec)
>  {
>  	u32	result;
> +	int	ret;
>  
> -	return readl_poll_timeout_atomic(ptr, result,
> -					 ((result & mask) == done),
> -					 delay_usec, wait_usec);
> +	ret = readl_poll_timeout_atomic(ptr, result,
> +					(result & mask) == done ||
> +					result == U32_MAX,
> +					delay_usec, wait_usec);
> +	if (result == U32_MAX)
> +		return -ENODEV;
> +
> +	return ret;

Nit:  Checking for PCI_POSSIBLE_ERROR(result) might be slightly clearer
than U32_MAX.

Thanks,

Lukas