Re: [PATCH v2 2/2] clk: mediatek: mt8365: Fix index issue

[Alexandre Mergnat]

On 26/05/2023 10:33, AngeloGioacchino Del Regno wrote:
> Il 25/05/23 16:50, Alexandre Mergnat ha scritto:
> > Before the patch [1], the clock probe was done directly in the
> > clk-mt8365 driver. In this probe function, the array which stores the
> > data clocks is sized using the higher defined numbers (*_NR_CLOCK) in
> > the clock lists [2]. Currently, with the patch [1], the specific
> > clk-mt8365 probe function is replaced by the mtk generic one [3], which
> > size the clock data array by adding all the clock descriptor array size
> > provided by the clk-mt8365 driver.
> >
> > Actually, all clock indexes come from the header file [2], that mean, if
> > there are more clock (then more index) in the header file [2] than the
> > number of clock declared in the clock descriptor arrays (which is the
> > case currently), the clock data array will be undersized and then the
> > generic probe function will overflow when it will try to write in
> > "clk_data[CLK_INDEX]". Actually, instead of crashing at boot, the probe
> > function returns an error in the log which looks like:
> > "of_clk_hw_onecell_get: invalid index 135", then this clock isn't
> > enabled.
> >
> > Solve this issue by adding in the driver the missing clocks declared in
> > the header clock file [2].
> >
> > [1]: Commit ffe91cb28f6a ("clk: mediatek: mt8365: Convert to
> >       mtk_clk_simple_{probe,remove}()")
> > [2]: include/dt-bindings/clock/mediatek,mt8365-clk.h
> > [3]: drivers/clk/mediatek/clk-mtk.c
> >
> > Fixes: ffe91cb28f6a ("clk: mediatek: mt8365: Convert to 
> > mtk_clk_simple_{probe,remove}()")
>
> This is not fixing the conversion, but the clock driver, as it 
> originally missed
> clock entries and hence was not compliant with its binding (header).
> It worked before, probably, but this doesn't mean that this driver 
> didn't contain
> a logic mistake from the beginning :-)
>
> So, add (or replace the current one with) the relevant Fixes tag...

Briefly and factually, the mt8365 clk probe mechanism was different

compared to the mtk clk driver. Even if it was an issue or not, it was

working (for sure). When [1] improved the mt8365 clk driver by using

the mtk clk generic probe, some clocks (USB here) no longer worked.

So, IMHO, it still a functional regression introduced by [1], because it

come from the switch of the probe function.


I'm not blaming & shaming the author of [1], as you said, it originally

missed clock entries and hence was not compliant with its binding

(whereas other MTK SoC was I guess). This commit is pointed thanks

to the bisect + test.


--
Regards,
Alexandre