* Grygorii Strashko <grygorii.strashko@xxxxxx> [151203 10:21]: > On 12/03/2015 06:37 PM, Tony Lindgren wrote: > > * Tony Lindgren <tony@xxxxxxxxxxx> [151203 08:34]: > >> > >> It seems we should apply this as a fix unless somebody has better ideas. > > > > Actually I think the fix for now is "[4.4-rc][PATCH v2] ARM: dts: am4372: fix > > clock source for arm twd and global timers" until PM starts working? > > > > Yes. if no PM it should work, but PM patches are on the fly for Am43. OK let's not merge this one then. > But, again, main reason I've posted this patch is that I do not see the > way how to enable/disable or limit functionality of these timer by using > Kconfig options in case of Muliplatform builds :( (or by boot parameters). > > Example 1 (this is how 4.4 kernel is working): > 1) OMAP4 has ARM TWD timer and properly supports it, so in Kconfig we have > "select HAVE_ARM_TWD" and corresponding "local-timer" is defined in DT. > AM437x has ARM TWD timer, but does not support it yet, so corresponding "local-timer" > defined in DT and in Kconfig HAVE_ARM_TWD is not selected. > (patch http://www.spinics.net/lists/arm-kernel/msg459649.html > is not merged yet) > > Result: ARM TWD timer will be enabled on AM437x !? :( > > Example 2: > ARM Global timer can't be used as clocksource device if CPUFreq is enabled > (this is not supported even by Timekeeping core now). > > So, there are two options: > 1) update selection for config SOC_AM43XX > + select ARM_GLOBAL_TIMER if !CPU_FREQ > 2) updated ARM GT driver and don't register clocksource device if CPUFreq is enabled > > Both options will not work: > 1) ARM_GLOBAL_TIMER will be selected if any other SoC in multiplatform build > will select ARM_GLOBAL_TIMER > 2) clocksource device will never be registered if at least one SoC will > select CPU_FREQ. And this might break SoC which expect it to be registered, > because CPU_FREQ is not enabled on these SoCs (no CPUFreq drivers registered). > > So, as alternative to this patch, ARM timers nodes can be disabled in > platform DTS files, but then all platform DTS files will need to be updated. Yes I don't see any other option right now until we have the clocksource switching happening. Only then will the scoring work properly. Regards, Tony -- 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
