linux-kernel - Re: [PATCH v9 1/5] clk: meson: add support for A1 PLL clock ops

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Date:   Mon, 6 Mar 2023 23:12:54 +0300
From:   Dmitry Rokosov <ddrokosov@...rdevices.ru>
To:     Jerome Brunet <jbrunet@...libre.com>
CC:     <neil.armstrong@...aro.org>, <mturquette@...libre.com>,
        <sboyd@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <khilman@...libre.com>,
        <martin.blumenstingl@...glemail.com>, <jian.hu@...ogic.com>,
        <kernel@...rdevices.ru>, <rockosov@...il.com>,
        <linux-amlogic@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v9 1/5] clk: meson: add support for A1 PLL clock ops

On Mon, Mar 06, 2023 at 12:09:35PM +0100, Jerome Brunet wrote:
> 
> On Wed 01 Mar 2023 at 21:37, Dmitry Rokosov <ddrokosov@...rdevices.ru> wrote:
> 
> > From: Jian Hu <jian.hu@...ogic.com>
> >
> > Modern meson PLL IPs are a little bit different from early known PLLs.
> > The main difference is located in the init/enable/disable sequences; the
> > rate logic is the same.
> 
> For the record, I find very odd that PLLs used to have an 'rst' bit in
> CTRL0:29 (see g12 for example), this bit goes un-documented in the a1
> datasheet, and following SoCs like s4 still have a rst bit, still in
> CTRL0:29
> 
> I would not be surpized if the rst is actually still there in the a1.
> It is just my guess ...
> 

We don't know it for sure. Datasheet doesn't have any information about
CTRL0:29 bit, CTRL0:28 (enable) bit is last one I see.
Vendor Amlogic driver doesn't have it in the init sequence as well.
BTW, vendor driver doesn't use clk_pll common logic, it achieves PLL
power-on goals using init_regs sequence.

> > Compared with the previous SoCs, self-adaption current module
> > is newly added for A1, and there is no reset parameter except the
> > fixed pll. In A1 PLL, the PLL enable sequence is different, using
> > the new power-on sequence to enable the PLL.
> 
> Please split this patch:
> #1 make the rst optional (if you must)
> #2 add the self current adapt param.
> 
> Apart from this, it looks good
> 

Thank you, I'll split it in the next version!

[...]
-- 
Thank you,
Dmitry