linux-kernel - Re: [PATCH 8/8] i2c: mediatek: modify bus speed calculation formula

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Date:   Thu, 15 Jul 2021 15:09:25 +0800
From:   Tzung-Bi Shih <tzungbi@...gle.com>
To:     Kewei Xu <kewei.xu@...iatek.com>
Cc:     wsa@...-dreams.de, matthias.bgg@...il.com, robh+dt@...nel.org,
        linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, srv_heupstream@...iatek.com,
        leilk.liu@...iatek.com, qii.wang@...iatek.com,
        qiangming.xia@...iatek.com, ot_daolong.zhu@...iatek.com
Subject: Re: [PATCH 8/8] i2c: mediatek: modify bus speed calculation formula

On Thu, Jul 15, 2021 at 10:32 AM Kewei Xu <kewei.xu@...iatek.com> wrote:
> When clock-div is 0 or greater than 1, the bus speed
> calculated by the old speed calculation formula will be
> larger than the target speed. So we update the formula.
The patch sounds like a fix up.  Need a "Fixes" tag.

>         for (clk_div = 1; clk_div <= max_clk_div; clk_div++) {
>                 clk_src = parent_clk / clk_div;
> +               i2c->ac_timing.inter_clk_div = clk_div - 1;
Using the way to pass the parameter "inter_clk_div" to
mtk_i2c_calculate_speed() looks like a hack.  inter_clk_div is set
again[1] next to the for loop.

[1]: https://elixir.bootlin.com/linux/v5.14-rc1/source/drivers/i2c/busses/i2c-mt65xx.c#L831



I have no domain knowledge of what/how the patch fixes.  But if this
is a standalone fixup patch, suggest separating to an independent
patch.