linux-kernel - Re: [PATCH 4.19 12/81] usb: xhci: wait for CNR controller not ready bit in xhci resume

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Message-ID: <20191018172843.GA27290@amd>
Date:   Fri, 18 Oct 2019 19:28:43 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Rick Tseng <rtseng@...dia.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: Re: [PATCH 4.19 12/81] usb: xhci: wait for CNR controller not ready
 bit in xhci resume

Hi!

> From: Rick Tseng <rtseng@...dia.com>
> 
> commit a70bcbc322837eda1ab5994d12db941dc9733a7d upstream.
> 
> NVIDIA 3.1 xHCI card would lose power when moving power state into D3Cold.
> Thus we need to wait for CNR bit to clear in xhci resume, just as in
> xhci init.
...

> @@ -1098,6 +1098,18 @@ int xhci_resume(struct xhci_hcd *xhci, b
>  		hibernated = true;
>  
>  	if (!hibernated) {
> +		/*
> +		 * Some controllers might lose power during suspend, so wait
> +		 * for controller not ready bit to clear, just as in xHC init.
> +		 */
> +		retval = xhci_handshake(&xhci->op_regs->status,
> +					STS_CNR, 0, 10 * 1000 * 1000);
> +		if (retval) {
> +			xhci_warn(xhci, "Controller not ready at resume %d\n",
> +				  retval);
> +			spin_unlock_irq(&xhci->lock);
> +			return retval;
> +		}

AFAICT if this error happens, xhci will be unusable. So maybe print
should be at higher level that warning... that's clearly an error.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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