linux-kernel - Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

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Date:   Thu, 26 Jan 2023 14:13:37 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>,
        linux-renesas-soc@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

Hi Wolfram,

On Thu, Jan 26, 2023 at 1:48 PM Wolfram Sang
<wsa+renesas@...g-engineering.com> wrote:
> > > +       regmap_update_bits(rpc->regmap, RPCIF_PHYCNT,
> > > +                          /* create mask with all affected bits set */
> > > +                          RPCIF_PHYCNT_STRTIM(BIT(fls(rpc->info->strtim)) - 1),
> >
> > fls(0) = 0, and BIT(-1) is undefined, so this won't work for R-Car
> > H3 ES1.x.  So I'm afraid you cannot handle this without storing the
> > actual mask ;-)
>
> You misread the parens, it is: BIT(0) - 1 = 0

Doh... You're right.

Still, it won't clear the bits on H3 ES1.x.
And when changing strtim to a value smaller than 4, it may not work
as expected, as it doesn't clear the upper bits.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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