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

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Date:   Sat, 6 Nov 2021 15:41:47 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:     stern@...land.harvard.edu, mr.yming81@...il.com,
        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
Subject: Re: [PATCH] xhci: Fix USB 3.1 enumeration issues by increasing
 roothub power-on-good delay

On Fri, Nov 05, 2021 at 09:56:59PM +0200, Mathias Nyman wrote:
> On 5.11.2021 18.15, Greg KH wrote:
> > On Fri, Nov 05, 2021 at 06:00:36PM +0200, 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>
> > 
> > So this needs:
> > 	Fixes: 90d28fb53d4a ("usb: core: reduce power-on-good delay time of root hub")
> > right?
> 
> I guess so, not sure on "Fixes" policy here.
> 
> This patch fixes an xhci issue revealed by ("usb: core: reduce power-on-good delay time of root hub")
> That original patch itself looks correct, but these two patches should really go together to
> avoid any enumeration issues.  

Great, I'll use that tag for now so that it will get backported
properly.

greg k-h