linux-kernel - Re: [PATCH] arm: dts: gr-peach: Reduce extal

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Date:   Wed, 4 Oct 2017 17:54:46 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Jacopo Mondi <jacopo+renesas@...ndi.org>
Cc:     Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Chris Brandt <Chris.Brandt@...esas.com>
Subject: Re: [PATCH] arm: dts: gr-peach: Reduce extal_clk resolution

Hi Jacopo,

On Wed, Oct 4, 2017 at 5:40 PM, Jacopo Mondi <jacopo+renesas@...ndi.org> wrote:
> The system clock described by extal_clk is reported to have a frequency
> of 13.333 Mhz and is correctly described by gr-peach device tree.
>
> However, when enabling a RIIC device the following error is reported by
> drivers/i2c/busses/i2c-riic.c
>
> "invalid parent clk (33332500). Must be 33325000Hz"
>
> As RIIC devices have a clock source obtained by dividing by 12 the
> system clock, the resulting value is not accepted by the driver
> (which clearly states not to support any frequency except the reported
> 33325000Hz one).
>
> Hence, reduce the system clock accuracy to a value which makes
> frequencies obtained through division accepted by RIIC driver.
>
> Please note that other r7s72100 boards, such as Genmai, report the same
> "reduced accuracy" frequency, even if their external clock sources are
> effectively 13.333Mhz as gr-peach one.
>
> Signed-off-by: Jacopo Mondi <jacopo+renesas@...ndi.org>

There's no need to do this, Chris already proposed a fix, cfr.
"[PATCH v2] i2c: riic: remove fixed clock restriction"
(https://www.spinics.net/lists/linux-renesas-soc/msg18573.html).

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