Re: [PATCH 1/1] clk: aspeed: Fix APLL calculate formula for ast2600-A2

[Joel Stanley]

On Tue, 19 Jan 2021 at 03:04, Ryan Chen <ryan_chen@xxxxxxxxxxxxxx> wrote:
>
> > -----Original Message-----
> > From: Joel Stanley <joel@xxxxxxxxxxxxx>
> > Sent: Tuesday, January 19, 2021 10:20 AM
> > To: Ryan Chen <ryan_chen@xxxxxxxxxxxxxx>; Michael Turquette
> > <mturquette@xxxxxxxxxxxx>; Stephen Boyd <sboyd@xxxxxxxxxx>;
> > linux-clk@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > andrewrj@xxxxxxxxxxx; BMC-SW <BMC-SW@xxxxxxxxxxxxxx>
> > Cc: joel@xxxxxxxxx; Andrew Jeffery <andrew@xxxxxxxx>
> > Subject: Re: [PATCH 1/1] clk: aspeed: Fix APLL calculate formula for ast2600-A2
> >
> > On Mon, 2021-01-18 at 18:08 +0800, Ryan Chen wrote:
> > > AST2600A1/A2 have different pll calculate formula.
> >
> > To clarify, only the A0 has the old calculation, and all subsequent revisions use
> > the new calculation?
> >
> > If this is the case, do we need to support A0 in mainline linux, or should we
> > drop support for A0 and only support A1, A2 and onwards?
> >
> A0/A1 is use older calculate formula
> After A2 is new calculate formula as the patch.

Thanks for clarifying. I suggest you change the commit log to say
something like this:

Starting from A2, the A-PLL calculation has changed. Use the existing
formula for A0/A1 and the new formula for A2 onwards.

>
> > You should add a line to indicate this is a fix:
> >
> > Fixes: d3d04f6c330a ("clk: Add support for AST2600 SoC")
> >
> Got it. so should I send new patch?

Yes, please consider adjusting the commit message as I suggested
above, and add the fixes line.

> > > +       u32 chip_id = readl(scu_g6_base + ASPEED_G6_SILICON_REV);
> > >
> > > -       if (val & BIT(20)) {
> > > -               /* Pass through mode */
> > > -               mult = div = 1;
> > > +       if (((chip_id & CHIP_REVISION_ID) >> 16) >= 2) {

Will this test be true if there are future versions of the chip (A3, etc)?

Cheers,

Joel