[lkml]   [2013]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v2 01/03] clocksource: Add Kconfig entries for CMT, MTU2, TMU and STI
On 11/27/2013 09:42 PM, Magnus Damm wrote:
> Hi John, everyone,
> Let me get back to you all in a little while together with some code,
> but before that let me just clarify this:
> On Wed, Nov 13, 2013 at 5:47 AM, John Stultz <> wrote:
>> On Tue, Nov 12, 2013 at 4:26 AM, Magnus Damm <> wrote:
>>> On Sat, Nov 9, 2013 at 3:34 AM, John Stultz <> wrote:
>>> Let me get back to the kernel configuration. Of course, it would be
>>> really nice if the kernel configuration was 100% fool proof, but what
>>> happens if the user doesn't compile-in certain parts? That hardware
>>> won't be used. What happens if wrong console device is passed on the
>>> kernel command line? The friendly answer is usually "don't do that".
>>> So in case of the serial console, no driver - no output. You can still
>>> use the network. If you have no timer then there won't be any timer
>>> ticks. You can still get to user space though, but don't try to rely
>>> on the timer. This CONFIG_TIMER=y/n case is pretty clear, but isn't
>>> there a grey zone too?
>> And on every new board, I have to fumble around with exactly those
>> sorts of no-serial output issues. Its never something I consider a
>> great use of my time :)
>> And your example is a little flawed have no timer ticks, you're not
>> getting to userspace. The system won't boot.
> Correct me if I'm wrong here but I don't think so!
> On some platforms that may very well be the case, but on mach-shmobile
> we get to user space without any timers. If the timers are enabled
> then they are regular platform devices these days. From my experience
> the main blocker for going to user space without timer is on ARM
> usually the udelay() calculation and/or the TWD delay, but those can
> be handled with preset worst-case values for udelay() and getting the
> rate via CCF for the TWD.
> Also it of course depends on if some compiled-in driver needs to use
> the timer. If we just enable the serial console then all our platforms
> make it to initramfs-based user space without any clock source or
> clock event.
So something still triggers basic HZ timer functionality, and you get by
with the jiffies clocksource?

Ok, so thanks for the correction. But I still think booting in a
degraded mode isn't ideal when the user has already provided enough info
via config options that we could have sorted it out for them.

But yea, I look forward to your next patch so we can discuss things more
concretely, rather then in my more abstract handwaving rants ;)


 \ /
  Last update: 2013-12-03 02:21    [W:0.068 / U:0.344 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site