Re: [PATCH V6 2/3] soc: qcom: boot_stat: Add Driver Support for Boot Stats

[Dmitry Baryshkov]

On 16/05/2023 11:19, Arnd Bergmann wrote:
> On Tue, May 9, 2023, at 12:52, 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 show the information within debugfs file.
> > This information is useful in verifying if the existing boot KPIs have
> > regressed or not. The information is shown in milliseconds, a sample
> > log from sm8450(waipio) device is as follows:-
> >
> > /sys/kernel/debug/qcom_boot_stats # cat abl_time
> > 17898 ms
> > /sys/kernel/debug/qcom_boot_stats # cat pre_abl_time
> > 2879 ms
> >
> > 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". Documentation
> > details are also added in Documentation/ABI/testing/debugfs-driver-bootstat
> >
> > Signed-off-by: Souradeep Chowdhury <quic_schowdhu@xxxxxxxxxxx>
> > ---
> >   .../ABI/testing/debugfs-driver-bootstat       |  17 +++
> >   drivers/soc/qcom/Kconfig                      |  10 ++
> >   drivers/soc/qcom/Makefile                     |   1 +
> >   drivers/soc/qcom/boot_stats.c                 | 100 ++++++++++++++++++
>
> As mentioned in my reply to the binding, I don't think this should
> be a driver at all. On top of that, even if it was a driver, it is
> clearly not a "soc" driver since nothing in it has any relevance to
> the hardware, rather than the first-stage loader, and drivers/soc/
> drivers should never have their own user space interface either.

I suppose that we should add a proper driver for imem rather than always 
using it through syscon.

--
With best wishes
Dmitry