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

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Message-ID: <20251219-visionary-hissing-sidewinder-5e95c5@sudeepholla>
Date: Fri, 19 Dec 2025 10:32:36 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Vedashree Vidwans <vvidwans@...dia.com>
Cc: <salman.nabi@....com>, <andre.przywara@....com>,
	Sudeep Holla <sudeep.holla@....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 Fri, Dec 19, 2025 at 12:38:39AM -0800, Vedashree Vidwans wrote:
> 
> 
> 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@sudeepholla
> 
> 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.
> 

Sure. I meant I don't see any patch titled "dt-bindings: firmware: Add LFA...."
or something similar. I also checked the delta for the files under
Documentation/devicetree/bindings/ to rule out the possibility that the
patch title may not be following the DT binding upstreaming process.

-- 
Regards,
Sudeep