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

[AngeloGioacchino Del Regno]

Il 25/10/23 11:50, Yu-chang Lee (李禹璋) ha scritto:
> On Tue, 2023-10-24 at 17:20 +0800, Chen-Yu Tsai wrote:
> >   	
> > External email : Please do not click links or open attachments until
> > you have verified the sender or the content.
> >   On Tue, Oct 24, 2023 at 3:47 PM Yu-chang Lee (李禹璋)
> > <Yu-chang.Lee@xxxxxxxxxxxx> 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@xxxxxxxxxx>
> > > > 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> > > > > >
> > > > > > 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?
>
> According to hardware designer it servers no purpose. Just a legacy of
> previous design...
>
> > 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
>
> After reviewing hardware design diagram, hardware designer concludes
> that the clock tree is indeed
>
> top_i2c -> infra_ao_i2c{4-6}
> top_i2c -> infra_ao_i2c_ap -> imp_iic_wrap_ap_clock_i2c{4-6}
>
> so I think we should keep this clock relation unchanged.
>
> Thanks
> YuChang

Can you please also expand on CLK_INFRA_AO_I2C{1,2,5}_ARBITER clocks?
Is the I2C arbiter also legacy of previous designs?

Please check [1], as I've sent a commit adding those in the devicetree.

Thanks,
Angelo

[1]: 
https://lore.kernel.org/all/20231020075540.15191-1-angelogioacchino.delregno@xxxxxxxxxxxxx/