linux-kernel - Re: [PATCH] thunderbolt: Reduce retry timeout to speed up boot for some devices

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Date: Wed, 20 Dec 2023 18:30:53 +0100
From: Greg KH <greg@...ah.com>
To: Werner Sembach <wse@...edocomputers.com>
Cc: Andreas Noever <andreas.noever@...il.com>,
	Michael Jamet <michael.jamet@...el.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Yehezkel Bernat <YehezkelShB@...il.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thunderbolt: Reduce retry timeout to speed up boot for
 some devices

On Wed, Dec 20, 2023 at 05:41:01PM +0100, Werner Sembach wrote:
> 
> Am 20.12.23 um 17:04 schrieb Greg KH:
> > On Wed, Dec 20, 2023 at 04:23:15PM +0100, Werner Sembach wrote:
> > > Am 20.12.23 um 16:09 schrieb Werner Sembach:
> > > > This is a followup to "thunderbolt: Workaround an IOMMU fault on certain
> > > > systems with Intel Maple Ridge".
> > > > 
> > > > It seems like the timeout can be reduced to 250ms. This reduces the overall
> > > > delay caused by the retires to ~1s. This is about the time other things
> > > > being initialized in parallel need anyway*, so like this the effective boot
> > > > time is no longer compromised.
> > > > 
> > > > *I only had a single device available for my measurements: A Clevo X170KM-G
> > > > desktop replacement notebook.
> > > > 
> > > > Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> > > I wonder if this could also land in stable? Or would it be to risky?
> > If it's really a bugfix now, why would it _not_ be relevant for stable?
> 
> Because it changes a timeout that could cause issues if set to low: This
> Patch sets to to 250ms. Set to 50ms it causes issues, currently it's 2000ms,
> 2 people tested that 250ms is enough, but i don't know if this is a big
> enough sample size for stable.

Remember, the next kernel will be a stable kernel tree, just like the
one after that.  If it's good enough for Linus's tree, why wouldn't it
be good enough for all stable trees?  Either it works or it doesn't,
none of this "we will break things when you move to a new kernel" stuff
please.

thanks,

greg k-h