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

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Message-ID: <CACPK8XfuiN_Nxfwf89ig5tgEo1dmiV_k092TVu527w4fYVFE0Q@mail.gmail.com>
Date:   Tue, 19 Jan 2021 03:10:05 +0000
From:   Joel Stanley <joel@....id.au>
To:     Ryan Chen <ryan_chen@...eedtech.com>
Cc:     Joel Stanley <joel@...ux.ibm.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "andrewrj@....ibm.com" <andrewrj@....ibm.com>,
        BMC-SW <BMC-SW@...eedtech.com>, Andrew Jeffery <andrew@...id.au>
Subject: Re: [PATCH 1/1] clk: aspeed: Fix APLL calculate formula for ast2600-A2

On Tue, 19 Jan 2021 at 03:04, Ryan Chen <ryan_chen@...eedtech.com> wrote:
>
> > -----Original Message-----
> > From: Joel Stanley <joel@...ux.ibm.com>
> > Sent: Tuesday, January 19, 2021 10:20 AM
> > To: Ryan Chen <ryan_chen@...eedtech.com>; Michael Turquette
> > <mturquette@...libre.com>; Stephen Boyd <sboyd@...nel.org>;
> > linux-clk@...r.kernel.org; linux-kernel@...r.kernel.org;
> > andrewrj@....ibm.com; BMC-SW <BMC-SW@...eedtech.com>
> > Cc: joel@....id.au; Andrew Jeffery <andrew@...id.au>
> > 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