From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <51124E54.603@xenomai.org> Date: Wed, 06 Feb 2013 13:36:36 +0100 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <51122E82.6050209@siemens.com> <51124A06.3020205@xenomai.org> <51124C88.1060401@siemens.com> <51124D37.1000001@xenomai.org> <51124DAD.3060306@siemens.com> In-Reply-To: <51124DAD.3060306@siemens.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] i8253 clocksource vs. rthal_get_8254_tsc List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Xenomai On 02/06/2013 01:33 PM, Jan Kiszka wrote: > On 2013-02-06 13:31, Gilles Chanteperdrix wrote: >> On 02/06/2013 01:28 PM, Jan Kiszka wrote: >> >>> On 2013-02-06 13:18, Gilles Chanteperdrix wrote: >>>> On 02/06/2013 11:20 AM, Jan Kiszka wrote: >>>> >>>>> Hi Gilles, >>>>> >>>>> I just realized that there is now a 8253 clocksource in core-3.4+. How >>>>> does this work together with Xenomai's TSC emulation via the 8254 in the >>>>> x86 hal_32? Xenomai reprograms the PIT in rthal_setup_8254_tsc - is this >>>>> harmless? >>>>> >>>>> I came across this while trying to get rid of Xenomai's "depends on >>>>> !INPUT_PCSPKR" to avoid that circular Kbuild dependency. >>>> >>>> >>>> This emulation replaces Xenomai's TSC emulation when the kernel boots on >>>> a cpu without a TSC: the detection is made at run-time instead of >>>> compilation time using self-modifying code (this in order to be able to >>>> build Debian kernels which boots with any configuration). >>> >>> Hmm, that's for the kernel. But what prevents rthal_setup_8254_tsc from >>> being executed in addition? I'm currently a bit lost in the #ifdefs. >> >> >> rthal_setup_8254_tsc is not called. >> >>> >>>> There is no >>>> reason to keep the compilation-time dependency on !INPUT_PCSPKR with >>>> I-pipe core, as now the pc speaker is disabled at run-time too. >>>> Unfortunately, I could not find how to arrange the Kconfig either. >>> >>> As this is only about practically unsupported combinations of Xenomai >>> (2.6.x) and I-pipe (for kernel 2.6.x) on x86, we could move from a >>> configure-time to a build-time detection (#ifdef CONFIG_INPUT_PCSPKR -> >>> BUILD_BUG()). >> >> >> There is already a run-time detection which simply does not declare the >> PC speaker platform device when there is no tsc. > > That's for core-3.4+, but not for older kernels. If we are fine with > ignoring them, I'll just write a patch to remove that Kconfig dependency. You could replace !INPUT_PCSPKR with !X86_TSC && !INPUT_PCSPKR I-pipe core kernels can be compiled with CONFIG_X86_TSC anyway. -- Gilles.