linux-kernel - Re: [RFC PATCH 0/5] Arm LFA: Improvements and interrupt support

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Message-ID: <8bca8c4b-52b8-4a1d-9f21-176c994a58bb@nvidia.com>
Date: Fri, 19 Dec 2025 00:38:39 -0800
From: Vedashree Vidwans <vvidwans@...dia.com>
To: Sudeep Holla <sudeep.holla@....com>
Cc: salman.nabi@....com, andre.przywara@....com, lpieralisi@...nel.org,
 mark.rutland@....com, ardb@...nel.org, chao.gao@...el.com,
 linux-arm-kernel@...ts.infradead.org, linux-coco@...ts.linux.dev,
 linux-kernel@...r.kernel.org, sdonthineni@...dia.com, vsethi@...dia.com,
 vwadekar@...dia.com
Subject: Re: [RFC PATCH 0/5] Arm LFA: Improvements and interrupt support



On 12/9/25 03:39, Sudeep Holla wrote:
> On Mon, Dec 08, 2025 at 10:13:10PM +0000, Vedashree Vidwans wrote:
>> Hello,
>>
>> The patches update the proposed Arm Live Firmware Activation (LFA)
>> kernel driver [1] to incorporate review feedback [2] and refine the
>> activation flow while remaining aligned with the LFA specification
>> DEN0147 [3] and the SMCCC 1.2 calling convention. The series keeps
>> the existing functionality but restructures and extends it to improve
>> robustness, reviewability, and future extensibility.
>>
>> The SMCCC usage in the driver is updated to consistently use the
>> SMCCC 1.2 register-based calling convention, consolidating arguments
>> and results into a single struct to reduce stack usage and simplify
>> the SMC interface. The patches also split the original changes into
>> focused pieces and document the device node bindings in the commit
>> messages, making it easier to follow and validate the implementation
>> against the specification.
>>
>> The kernel driver is registered as a platform driver in accordence to
>> the LFA device defined by the specification [3]. The driver now extends
>> interface for interrupt-based enablement of LFA. During LFA, the
>> interrupt
>> thread refreshes firmware component details after each activation step
>> and iterates over all activable components until no further activation
>> is pending, matching the spec’s allowance for component detail changes
>> after activation. This ensures that sysfs exposure of LFA components
>> remains consistent with the authoritative information provided by the
>> secure firmware.
>>
>> The handling of CPU rendezvous is adjusted so that the kernel now
>> honors the rendezvous policy chosen by the firmware, instead of
>> unconditionally forcing a rendezvous. This reflects experience with
>> existing firmware deployments where mandatory rendezvous is not
>> required, while still allowing the firmware to request it when
>> needed.
>>
>> Thank you,
>> Veda
>>
>> [1] https://lore.kernel.org/lkml/20250926123145.268728-1-salman.nabi@arm.com/
>> [2] https://lkml.org/lkml/2025/10/8/980
>> [3] https://developer.arm.com/documentation/den0147/latest/
>>
>> Vedashree Vidwans (5):
>>    firmware: smccc: LFA: use smcc 1.2
>>    firmware: smccc: LFA: refactor
>>    firmware: smccc: add timeout, touch wdt
>>    firmware: smccc: register as platform driver
>>    firmware: smccc: lfa: refresh fw details
>>
>>   drivers/firmware/smccc/Kconfig  |   3 +-
>>   drivers/firmware/smccc/lfa_fw.c | 478 +++++++++++++++++++++++++-------
> 
> Same comment as before[1], looks like the feedback got ignored or missed.
> 
> -- 
> Regards,
> Sudeep
> 
> [1]https://lore.kernel.org/all/20251009-calculating-glorious-oriole- 
> ceccf6@...eepholla

Thank you for your comment.
I did include DT binding in commit message of the patch. Please let me 
know if there's anything else I can elaborate.

Regards,
Veda