linux-kernel - Re: [PATCH 00/18] mfd: convert to use maple tree register cache

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Date: Tue, 6 Feb 2024 11:14:11 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Mark Brown <broonie@...nel.org>
Cc: Bo Liu <liubo03@...pur.com>, lee@...nel.org, wens@...e.org, 
	marek.vasut+renesas@...il.com, support.opensource@...semi.com, 
	neil.armstrong@...aro.org, ckeepax@...nsource.cirrus.com, 
	rf@...nsource.cirrus.com, mazziesaccount@...il.com, mcoquelin.stm32@...il.com, 
	alexandre.torgue@...s.st.com, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-amlogic@...ts.infradead.org, 
	patches@...nsource.cirrus.com, linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 00/18] mfd: convert to use maple tree register cache

Hi Mark,

On Tue, Feb 6, 2024 at 11:09 AM Mark Brown <broonie@...nel.org> wrote:
> On Tue, Feb 06, 2024 at 10:33:22AM +0100, Geert Uytterhoeven wrote:
> > If all of this is true, is there any reason to keep REGCACHE_RBTREE
> > around?  If not, perhaps REGCACHE_RBTREE should be treated as
> > REGCACHE_MAPLE in the regmap core code first, followed by a single
> > tree-wide patch to replace REGCACHE_RBTREE?
>
> There is a very small niche for devices where cache syncs are a
> particularly important part of the workload where rbtree's choices might
> give better performance, especially on systems with low end CPUs.

The REGCACHE_* value is specified by the device, not by the CPU?
While some of these MFD devices are on-SoC, and thus there is some
relation between device and CPU, several others (e.g. PMICs) are
external, and thus might be present on systems with a variety of CPU
performance.

Perhaps the value should depend on some CPU heuristic instead?

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds