On Mon, Jul 16, 2018 at 5:33 AM Dou Liyang <douly.fnst@xxxxxxxxxxxxxx> wrote: > > > > At 07/13/2018 07:30 PM, Pavel Tatashin wrote: > > On Fri, Jul 13, 2018 at 3:24 AM Dou Liyang <douly.fnst@xxxxxxxxxxxxxx> wrote: > >> > >> > >> At 07/12/2018 08:04 AM, Pavel Tatashin wrote: > >>> During boot tsc is calibrated twice: once in tsc_early_delay_calibrate(), > >>> and the second time in tsc_init(). > >>> > >>> Rename tsc_early_delay_calibrate() to tsc_early_init(), and rework it so > >>> the calibration is done only early, and make tsc_init() to use the values > >>> already determined in tsc_early_init(). > >>> > >>> Sometimes it is not possible to determine tsc early, as the subsystem that > >>> is required is not yet initialized, in such case try again later in > >>> tsc_init(). > >>> > >>> Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > >>> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > >> > >> Hi Pavel, > >> > >> Aha, a complex solution for a simple problem! ;-) And I did find any > >> benefits of doing that. did I miss something? > > > > Hi Dou, > > > > I had this in previous version: init early, and unconditionally > > re-init later (which required to resync sched clocks for continuity, > > and check for some other corner cases). Thomas did not like the idea, > > as it is less deterministic: it leads for code to work by accident, > > where we might get one tsc frequency early and another later, and so > > on. The request was to initialize only once, and if that fails do it > > again later. This way, if early initialization is broken, we will know > > and fix it. > > > > Hi Pavel, > > Yes, right, I have seen the purpose in v12. > > >> > >> As the cpu_khz and tsc_khz are global variables and the tsc_khz may > >> be reset to cpu_khz. How about the following patch. > > > > Could you please explain where you think this patch can be applied, > > and what it fixes? > > > > This patch is just an simple alternative to realize what you want in > your patch. your patch is also good but complex, and need some scrub. > eg: > - Is it suitable to using the WARN_ON() > - the name of determine_cpu_tsc_frequncies() function, > s/frequncies/frequencies/. BTW, How about tsc_calibrate_frequencies() > - ... > > BTW, before this patch, seems we need make sure xen should work well, I > can investigate and try to test if we can also move the pagetable_init() > to the front of tsc_early_init() for you. v13 has xen patches, so xen timestamps work early as well now. Thank you, Pavel -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
