linux-kernel - Re: [PATCH 2/2] spi: rpc-if: Remove CONFIG_PM

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Message-ID: <20210105104234.GA29908@amd>
Date:   Tue, 5 Jan 2021 11:42:34 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Pavel Machek <pavel@...x.de>, Mark Brown <broonie@...nel.org>,
        "Lad, Prabhakar" <prabhakar.csengg@...il.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Jiri Kosina <trivial@...nel.org>,
        Sergei Shtylyov <sergei.shtylyov@...il.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Chris Brandt <Chris.Brandt@...esas.com>
Subject: Re: [PATCH 2/2] spi: rpc-if: Remove CONFIG_PM_SLEEP ifdefery

Hi!

> On Tue, Jan 5, 2021 at 12:40 AM Pavel Machek <pavel@...x.de> wrote:
> > > > > >                 .name   = "rpc-if-spi",
> > > > > > -               .pm     = DEV_PM_OPS,
> > > > > > +               .pm     = &rpcif_spi_pm_ops,
> > >
> > > > > You're aware rpcif_spi_pm_ops is now always referenced and thus emitted,
> > > > > increasing kernel size by 92 bytes if CONFIG_PM_SLEEP=n?
> > > > > This may matter for RZ/A SoCs running from internal SRAM.
> > >
> > > > Hmm didn't realise this would be an issue on RZ/A.
> > >
> > > > Mark, could you please drop this patch from your branch.
> > >
> > > Please send an incremental patch with an appropriate changelog.
> >
> > Let's fix this properly. I'm pretty sure we have some macros that can
> > solve this without re-introducing the ifdefs...
> 
> There's pm_ptr(), but it uses CONFIG_PM as a selector, not CONFIG_PM_SLEEP.

Okay; so we could introduce pm_sleep_ptr().

Or we could just put single #ifdef CONFIG_PM_SLEEP around the .pm
assignment? That would be improvement on the original, and still
result in the same binary, right?

> > (Besides... 92 bytes. How big is kernel these days? 4MB? More? How
> > much SRAM do you have?)
> 
> 92 bytes is indeed not much (on 64-bit it would be doubled).
> Still, it's good to make people think about innocent looking changes,
> once in a while.
> 
> RZ/A1H and RZ/A1M have 10 resp. 5 MiB of SRAM.
> RZ/A2 has 4 MiB SRAM, which is sufficient to run Linux when used with
> XIP (requires a one-line Kconfig change rmk has been vetoing for
 > years).

Aha, that is a bit smaller than I expected.

Best regards,
								Pavel

-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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