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

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Message-ID: <20251209-miniature-curassow-of-energy-b6a303@sudeepholla>
Date: Tue, 9 Dec 2025 11:39:40 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Vedashree Vidwans <vvidwans@...dia.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>,
	Sudeep Holla <sudeep.holla@....com>, <vwadekar@...dia.com>
Subject: Re: [RFC PATCH 0/5] Arm LFA: Improvements and interrupt support

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@sudeepholla