Messages in this thread | | | Date | Wed, 12 Apr 2023 19:52:01 +0530 | Subject | Re: [PATCH V2 2/3] soc: qcom: boot_stat: Add Driver Support for Boot Stats | From | Souradeep Chowdhury <> |
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On 4/12/2023 1:47 PM, Krzysztof Kozlowski wrote: > On 10/04/2023 08:48, Souradeep Chowdhury wrote: >> >> >> On 4/7/2023 9:11 PM, Bjorn Andersson wrote: >>> On Fri, Apr 07, 2023 at 07:34:36PM +0530, Souradeep Chowdhury wrote: >>>> All of Qualcomm's proprietary Android boot-loaders capture boot time >>>> stats, like the time when the bootloader started execution and at what >>>> point the bootloader handed over control to the kernel etc. in the IMEM >>>> region. This information is captured in a specific format by this driver >>>> by mapping a structure to the IMEM memory region and then accessing the >>>> members of the structure to print the information. This information is >>>> useful in verifying if the existing boot KPIs have regressed or not. >>>> A sample log in SM8450(waipio) device is as follows:- >>>> >>>> KPI: Pre ABL Time = 3s >>>> KPI: ABL Time = 14s >>> >>> Why are these in whole seconds? >> >> This is to give a granular view of time. >> >>> >>>> KPI: Kernel MPM timestamp = 890206 >>> >>> And why is this presented in cycles? >> >> This timestamp is used as an intermediate value for calculating one of >> the KPIs. Can be changed to seconds as well for consistency. >> >>> >>>> >>>> The Module Power Manager(MPM) sleep counter starts ticking at the PBL >>>> stage and the timestamp generated by the sleep counter is logged by >>>> the Qualcomm proprietary bootloader(ABL) at two points-> First when it >>>> starts execution which is logged here as "Pre ABL Time" and the second >>>> when it is about to load the kernel logged as "ABL Time". Both are >>>> logged in the unit of seconds. >>> >>> We have a policy to not taint the kernel log with "useless" information, >>> for kernel developers this seems to add no value and for end users >>> there's no benefit to this. >>> >>>> The current kernel timestamp is >>>> printed by the boot_stats driver as well. >>>> >>> >>> Why? >> >> Same as stated above. > > You did not answer. The question is "why do you think printing this > during boot is suitable for wide usage?". I don't find answer "give a > granular view of time" anyway related. > > Please come with rationale why such printing should be used in Linux > kernel at all, given that as Bjorn said - we do not print > debugging/profiling information. > > You should probably come with a debugfs interface for this.
Ack. The debugfs interface for this will be present in the next version.
> > Best regards, > Krzysztof >
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