[GIT PULL] Qualcomm driver updates for v6.3

[Souradeep Chowdhury]

On 2/22/2023 5:43 PM, Leo Yan wrote:
> Hi Souradeep,
> 
> On Wed, Feb 22, 2023 at 04:46:07PM +0530, Souradeep Chowdhury wrote:
>> On 2/22/2023 7:13 AM, Leo Yan wrote:
>>> On Wed, Feb 15, 2023 at 04:05:36PM +0100, Arnd Bergmann wrote:
> 
> [...]
> 
>>>> If the possible use is purely for saving some state across
>>>> a reboot, as opposed to other events, I wonder if there is
>>>> a good way to integrate it into the fs/pstore/ code, which
>>>> already has a way to multiplex various kinds of input (log
>>>> buffer, ftrace call chain, userspace strings, ...) into
>>>> various kinds of persistent buffers (sram, blockdev, mtd,
>>>> efivars, ...) with the purpose of helping analyze the
>>>> state after a reboot.
>>>
>>> Good point!
>>>
>>> I understand pstore/ramoops is somehow like a sink which routes the
>>> tracing data (software tracing data but not hadware tracing data) to
>>> persistent memory.  This is why we also can route these software
>>> tracing data to STM (hardware sink!).
>>>
>>> Seems to me, Arnd suggests to connect two sinks between DCC and
>>> pstore (to persistent memory).  But I cannot give an example code in
>>> kernel for doing this way, sorry if I miss something.
>>>
>>> Essentially, a good user case is to keep a persistent memory for the
>>> tracing data, then after rebooting cycle we can retrieve the tracing
>>> data via user space interface (like sysfs node).
>>
>> Hi Leo/Arnd,
>>
>> Just wanted to let you know that the justification of not using PStore was
>> already given in the version 1 of this patch series as below
>>
>> https://lore.kernel.org/linux-arm-msm/ab30490c016f906fd9bc5d789198530b@codeaurora.org/#r
>>
>> PStore/Ramoops only persists across warm-reboots which is present for chrome
>> devices but not for android ones.
> 
> Thanks for the info.  Just remind a subtle difference of reboots.
> 
> Besides warm reboot, kernel can reboot system after panic (see kernel
> command line option `panic`) and watchdog can reboot the system as well.
> 
> Even though Android doesn't support warm reboot, system still can reboot
> on panic or by watchdog (in particular after bus lockup), pstore/ramoops
> also can support these cases.


So for the SoCs that doesn't support warm reboots, the DDR memory is non
persistent across panics or watchdog bites in which case the 
PStore/Ramoops cannot be of use.


> 
>> Also the dcc_sram contents can
>> also be collected by going for a software trigger after loading the kernel
>> and the dcc_sram is parsed to get the register values with the
>> opensource parser as below
>>
>> https://source.codeaurora.org/quic/la/platform/vendor/qcom-opensource/tools/tree/dcc_parser
> 
> To be clear, current driver is fine for me (TBH, I didn't spend much
> time to read it but it's very neat after quickly went through it), I
> just share some info in case it's helpful for the discussion.
> 
> Thanks,
> Leo