linux-kernel - Re: [PATCH v5 02/44] clk: davinci: New driver for davinci PLL clocks

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Message-ID: <eb2b1a63-9c7c-aeca-170f-d38642442438@ti.com>
Date:   Fri, 12 Jan 2018 21:48:15 +0530
From:   Sekhar Nori <nsekhar@...com>
To:     David Lechner <david@...hnology.com>, <linux-clk@...r.kernel.org>,
        <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Kevin Hilman <khilman@...nel.org>,
        Adam Ford <aford173@...il.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 02/44] clk: davinci: New driver for davinci PLL clocks

On Friday 12 January 2018 08:55 PM, David Lechner wrote:
>>
>> PLL output on DA850 must never be below 300MHz or above 600MHz (see
>> datasheet table "Allowed PLL Operating Conditions"). Does this take care
>> of that? Thats one of the main reasons I recall I went with some
>> specific values of prediv, pllm and post div in
>> arch/arm/mach-davinci/da850.c
> 
> Apparently, I missed this requirement. It looks like I am going to have to
> rework things so that there is some coordination between the PLL and the
> PLLDIV clocks in order to get the < 300MHz operating points.

Just to make sure we are on the same page. The datasheet
constraint is 600 >= PLLOUT >= 300. PLLOUT is output of POSTDIV.

The operating points are defined in terms of ARM frequency (and
voltage). The OPPs defined in kernel today are here:
https://git.kernel.org/pub/scm/linux/kernel/git/nsekhar/linux-davinci.git/tree/arch/arm/mach-davinci/da850.c#n1092

Thanks,
Sekhar