linux-kernel - Re: [PATCH] clk: mediatek: mt8186: Change I2C 4/5/6 ap clocks parent to infra

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Date:   Tue, 24 Oct 2023 17:20:11 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Yu-chang Lee (李禹璋) 
        <Yu-chang.Lee@...iatek.com>
Cc:     "sboyd@...nel.org" <sboyd@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        Chun-Jie Chen (陳浚桀) 
        <Chun-Jie.Chen@...iatek.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Miles Chen (陳民樺) 
        <Miles.Chen@...iatek.com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "angelogioacchino.delregno@...labora.com" 
        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH] clk: mediatek: mt8186: Change I2C 4/5/6 ap clocks parent
 to infra

On Tue, Oct 24, 2023 at 3:47 PM Yu-chang Lee (李禹璋)
<Yu-chang.Lee@...iatek.com> wrote:
>
> On Tue, 2023-10-24 at 10:58 +0800, Chen-Yu Tsai wrote:
> > On Tue, Oct 24, 2023 at 10:52 AM Stephen Boyd <sboyd@...nel.org>
> > wrote:
> > >
> > > Quoting Chen-Yu Tsai (2023-10-19 22:06:35)
> > > > On Thu, Oct 19, 2023 at 8:49 PM AngeloGioacchino Del Regno
> > > > <angelogioacchino.delregno@...labora.com> wrote:
> > > > >
> > > > > Fix the parenting of clocks imp_iic_wrap_ap_clock_i2c{4-6}, as
> > > > > those
> > > > > are effectively parented to infra_ao_i2c{4-6} and not to the
> > > > > I2C_AP.
> > > > > This permits the correct (and full) enablement and disablement
> > > > > of the
> > > > > I2C4, I2C5 and I2C6 bus clocks, satisfying the whole clock tree
> > > > > of
> > > > > those.
> > > > >
> > > > > As an example, when requesting to enable
> > > > > imp_iic_wrap_ap_clock_i2c4:
> > > > >
> > > > > Before: infra_ao_i2c_ap -> imp_iic_wrap_ap_clock_i2c4
> > > > > After:  infra_ao_i2c_ap -> infra_ao_i2c4 ->
> > > > > imp_iic_wrap_ap_clock_i2c4
> > > > >
> > > > > Fixes: 66cd0b4b0ce5 ("clk: mediatek: Add MT8186 imp i2c wrapper
> > > > > clock support")
> > > > > Signed-off-by: AngeloGioacchino Del Regno <
> > > > > angelogioacchino.delregno@...labora.com>
> > > >
> > > > I'm curious about what led to discovering this error?
> > > >
> > >
> > > Is that an acked-by?
> >
> > MediaTek engineers are saying the original code already matches the
> > documentation provided by their hardware engineers. I'm trying to get
> > them to respond on the mailing list.
> >
> > ChenYu
> >
> After checking with I2C clock hardware designer there is no
> infra_ao_i2c{4-6} clock gate in between. And the clock document at hand
> aslo shows the same result. Generallly speaking, we would like to keep
> sw setting align with the hardware design document. I would recommand
> not to change this part of code, but enable infra_ao_i2c{4-6} prior to
> the usage of imp_iic_wrap_ap_clock_i2c clock.

Are infra_ao_i2c{4-6} actually used by the hardware? If so, for what purpose?
If it is actually needed by the hardware and it is not in the existing path,
then it needs to be described in the device tree and handled by the driver.

ChenYu