On Wed, Oct 21, 2015 at 01:09:55PM -0500, Rob Herring wrote: > On Wed, Oct 21, 2015 at 11:06 AM, Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > On Wed, Oct 21, 2015 at 05:53:13PM +0200, Tomeu Vizoso wrote: > >> On 21 October 2015 at 17:14, Greg Kroah-Hartman > >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >> > On Wed, Oct 21, 2015 at 04:35:58PM +0200, Tomeu Vizoso wrote: > >> >> On 21 October 2015 at 05:39, Greg Kroah-Hartman > >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >> >> > On Tue, Oct 20, 2015 at 06:17:39PM +0200, Tomeu Vizoso wrote: > >> >> >> On 20 October 2015 at 16:05, Greg Kroah-Hartman > >> >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >> >> >> > On Tue, Oct 20, 2015 at 09:40:48AM +0200, Tomeu Vizoso wrote: > >> >> >> >> On 19 October 2015 at 17:19, Greg Kroah-Hartman > >> >> >> >> <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > >> >> >> >> > On Mon, Oct 19, 2015 at 05:13:22PM +0200, Tomeu Vizoso wrote: > >> >> >> >> >> To smooth the transition to late probes, make disabled the default for > >> >> >> >> >> DELAY_DEVICE_PROBES and let individual SoCs enable the option as they > >> >> >> >> >> get fixed. > >> >> >> >> >> > >> >> >> >> >> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> > >> >> >> >> >> Link: https://lkml.kernel.org/g/20151016181129.GA1764@xxxxxxxxxxxx > >> >> >> >> >> > >> >> >> >> >> --- > >> >> >> >> >> > >> >> >> >> >> Hi Rob, > >> >> >> >> >> > >> >> >> >> >> I'm sending this in case you think it would be best to leave the > >> >> >> >> >> on-demand probe series in -next for now but have late probes disabled to > >> >> >> >> >> avoid hassle to some people. > >> >> >> >> > > >> >> >> >> > I would like Rob to just drop this series please, I don't agree with it > >> >> >> >> > at all at the moment. > >> >> >> >> > >> >> >> >> Hi Greg, > >> >> >> >> > >> >> >> >> is it the case that you are satisfied with deferred probes as a way of > >> >> >> >> ordering device probing and that I should look at how to solve my > >> >> >> >> problem by improving it? > >> >> >> > > >> >> >> > Yes, especially given that you have said this does not speed up your > >> >> >> > boot times, which I thought was your main goal here :( > >> >> >> > >> >> >> Sorry if I'm repeating myself too often, but I have two goals: change > >> >> >> the probing order to not send deferred probes to the back of the queue > >> >> >> (getting the display up as fast as possible), and making easier to > >> >> >> understand the boot process on embedded platforms. > >> >> >> > >> >> >> The concrete issue that would be fixed by achieving the first goal was > >> >> >> explained in this email from last year: > >> >> >> > >> >> >> http://lists.freedesktop.org/archives/dri-devel/2014-August/066527.html > >> >> >> > >> >> >> Because of that, ChromeOS had to use their own bindings for the panel > >> >> >> node so that the panel probe wouldn't be deferred, introducing a > >> >> >> sizable delta that is a barrier to rebasing on newer mainline releases > >> >> >> and for vendors to upstream their HW adaptation for chrome devices. > >> >> > > >> >> > 1.5 second delay is crazy (again, my laptop boots to X in less time than > >> >> > that), > >> >> > >> >> 1.5 seconds isn't crazy at all for the kernel to initialize all the > >> >> devices in an embedded board. That's the current state of affairs > >> >> today. > >> > > >> > Then someone needs to fix that, that really is crazy. What takes so > >> > long here? Why aren't you using async probing to do things in parallel > >> > when you need to sleep in device probe (I'm hoping you are sleeping in > >> > device probe, otherwise that's really broken)? > >> > >> I'm a bit surprised now. During all the time that I have been pushing > >> this forward I have been regularly testing on more than a dozen boards > >> with different socs and 1.5 seconds to probe all the devices isn't > >> that much. This is basically due to having to wait for the hardware a > >> bit here and there, and to the sheer number of devices involved. > >> > >> Of course people have been looking at speeding up boot on ARM devices > >> for years now and this is what we have come with up to now. > >> > >> > Have you used the tools we have to find where the time is being spent? > >> > >> Have to recognize that my starting point has been that probe order was > >> the cause of the problem and haven't profiled the whole boot process, > >> but I don't see how probe ordering would become irrelevant unless we > >> got total probing time down to 200ms. And that would give us a > >> fabulously fast boot, which I don't think is as realistic as you seem > >> to believe. > > > > So you aren't using the tools that we have today that were created years > > ago, to help to reduce boot time problems like this and instead work on > > changing the driver core to try to guess at what the real issue is here? > > > > Come on, until you really know where you are taking so long, how can you > > know what you need to fix? I strongly recommend doing that here first, > > that's why those tools were written in the first place. > > For something everyone is or should be doing for years, there is > surprisingly zero information I can find. It is perf timechart you are > talking about, right? Everything I find on it is all after userspace > starts. I know perf has command line options, but I never could get it > to do what I wanted (which was dumping events up until a boot hang). scripts/bootgraph.pl combined with 'initcall_debug' on the kernel command line. Landed in Linus's tree back in 2008, perf is not needed. thanks, greg k-h -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
