linux-kernel - Re: [RFC PATCH 0/1] Add driver to read secondary bootloader (XBL) log

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Date:   Mon, 28 Aug 2023 22:49:01 +0530
From:   Arun Kumar Neelakantam <quic_aneelaka@...cinc.com>
To:     Ninad Naik <quic_ninanaik@...cinc.com>, <agross@...nel.org>,
        <andersson@...nel.org>, <konrad.dybcio@...aro.org>
CC:     <psodagud@...cinc.com>, <quic_ppareek@...cinc.com>,
        <quic_kprasan@...cinc.com>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>, <kernel@...cinc.com>
Subject: Re: [RFC PATCH 0/1] Add driver to read secondary bootloader (XBL) log



On 8/22/2023 5:45 PM, Ninad Naik wrote:
> Boot time logs for Qualcomm secondary boot-loader or XBL can help to
> identify different set of information regarding firmware configuration,
> SoC boot KPIs. A dedicated region is carved out in the memory map in order
> to store this log in the memory.
> 
> The objective of this driver is to read the XBL boot log stored in
> this memory region post boot-up, and provide an entry in debugfs, which
> can be used to read back the logs and print them on to the console.
> 

I see couple of use cases for this kind of logging like logs from boot, 
Hypervisor, Trusted Execution environments and also one in upstream for 
chromeos EC console. Can this be made a generic driver which take log 
name, log memory buffer address and size to read from debugfs.
> Further, this log can be parsed to extract different set of information
> as required.
> 
> For example, one use case can be parsing boot time KPIs to calculate,
>   - PBL End time
>   - SBL End time
>   - UEFI Start/Stop time
> 
> Corresponding log contents as captured in /sys/kernel/debug/xbl_log entry
> which prints the above counters,
> 
>          S -     59378 - PBL, End
>          B -     68198 - SBL1, Start
>          B -   1308877 - SBL1, End
>          UEFI Start     [ 3370]
>           - 0x0AF001000 [ 3375] Sec.efi
>          UEFI Total : 466 m
>          POST Time      [ 3836] OS Loader
>           - 0x0ABE10000 [ 3838] LinuxLoader.efi
>          Exit EBS        [ 4878] UEFI End
> 
>          /* Note - these are few excerpts picked from the complete XBL log
>           *        as tested on SA8775p
>           */
> 
> Ninad Naik (1):
>    soc: qcom: Add driver to read secondary bootloader (XBL) log
> 
>   drivers/soc/qcom/Kconfig        |  13 +++
>   drivers/soc/qcom/Makefile       |   1 +
>   drivers/soc/qcom/dump_xbl_log.c | 139 ++++++++++++++++++++++++++++++++
>   3 files changed, 153 insertions(+)
>   create mode 100644 drivers/soc/qcom/dump_xbl_log.c
>