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. Best regards, Krzysztof
