linux-kernel - Re: [PATCH] xhci: Fix USB 3.1 enumeration issues by increasing roothub power-on-good delay

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Message-ID: <96925c96-0f87-f110-e279-5b669337948a@linux.intel.com>
Date:   Fri, 5 Nov 2021 18:09:03 +0200
From:   Mathias Nyman <mathias.nyman@...ux.intel.com>
To:     "Walt Jr. Brake" <mr.yming81@...il.com>
Cc:     chunfeng.yun@...iatek.com, matthias.bgg@...il.com,
        nishadkamdar@...il.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, eddie.hung@...iatek.com,
        Alan Stern <stern@...land.harvard.edu>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] xhci: Fix USB 3.1 enumeration issues by increasing
 roothub power-on-good delay

On 5.11.2021 18.00, Mathias Nyman wrote:
> Some USB 3.1 enumeration issues were reported after the hub driver removed
> the minimum 100ms limit for the power-on-good delay.
> 
> Since commit 90d28fb53d4a ("usb: core: reduce power-on-good delay time of
> root hub") the hub driver sets the power-on-delay based on the
> bPwrOn2PwrGood value in the hub descriptor.
> 
> xhci driver has a 20ms bPwrOn2PwrGood value for both roothubs based
> on xhci spec section 5.4.8, but it's clearly not enough for the
> USB 3.1 devices, causing enumeration issues.
> 
> Tests indicate full 100ms delay is needed.
> 
> Reported-by: Walt Jr. Brake <mr.yming81@...il.com>
> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
> 

Walt Jr Brake, just to be sure could you test this one as well?

As Alan suggested this sets 100ms for the USB 3 roothub but
keeps the 20ms for the USB 2 roothub.

Thanks
-Mathias