On 10/21/2015 2:12 PM, Rob Herring wrote: > On Wed, Oct 21, 2015 at 1:18 PM, Frank Rowand <frowand.list@xxxxxxxxx> wrote: >> On 10/21/2015 9:27 AM, Mark Brown wrote: >>> On Wed, Oct 21, 2015 at 08:59:51AM -0700, Frank Rowand wrote: >>>> On 10/19/2015 5:34 AM, Tomeu Vizoso wrote: >>> >>>>> To be clear, I was saying that this series should NOT affect total >>>>> boot times much. >>> >>>> I'm confused. If I understood correctly, improving boot time was >>>> the key justification for accepting this patch set. For example, >>>> from "[PATCH v7 0/20] On-demand device probing": >>>> >>>> I have a problem with the panel on my Tegra Chromebook taking longer >>>> than expected to be ready during boot (Stéphane Marchesin reported what >>>> is basically the same issue in [0]), and have looked into ordered >>>> probing as a better way of solving this than moving nodes around in the >>>> DT or playing with initcall levels and linking order. >>>> >>>> ... >>>> >>>> With this series I get the kernel to output to the panel in 0.5s, >>>> instead of 2.8s. >>> >>> Overall boot time and time to get some individual built in component up >>> and running aren't the same thing - what this'll do is get things up >>> more in the link order of the leaf consumers rather than deferring those >>> leaf consumers when their dependencies aren't ready yet. >> >> Thanks! I read too much into what was being improved. >> >> So this patch series, which on other merits may be a good idea, is as >> a by product solving a specific ordering issue, moving successful panel >> initialization to an earlier point in the boot sequence, if I now >> understand more correctly. >> >> In that context, this seems like yet another ad hoc way of causing the >> probe order to change in a way to solves one specific issue? Could >> it just as likely move the boot order of some other driver on some >> other board later, to the detriment of somebody else? > > Time to display on is important for many products. Having the console > up as early as possible is another case. CAN bus is another. This is a > real problem that is not just bad drivers. Yes, I agree. What I am seeing is that there continues to be a need for the ability to explicitly order at least some driver initialization (at some granularity), despite the push back against explicit ordering that has been present in the past. > I don't think it is completely ad hoc. Given all devices are > registered after drivers, drivers will still probe first in initcall > level order and then link order AFAIK. We may not take (more) initcall > level tweak hacks, but that is a much more simple change for > downstream. Don't get me wrong, I'd really like to see a way to > control order independent of initcall level. > > Rob Yep, it is not directly ad hoc, just a fortunate side effect in this case. So just accidently ad hoc. :-) -Frank -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
