linux-kernel - RE: [PATCH v6 04/11] firmware: xilinx: Add query data API

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Message-ID: <SN1PR02MB375832594C7B5684888B213BB8930@SN1PR02MB3758.namprd02.prod.outlook.com>
Date:   Tue, 15 May 2018 20:29:15 +0000
From:   Jolly Shah <JOLLYS@...inx.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        "mturquette@...libre.com" <mturquette@...libre.com>,
        "sboyd@...eaurora.org" <sboyd@...eaurora.org>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
CC:     Rajan Vaja <RAJANV@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v6 04/11] firmware: xilinx: Add query data API

Hi Sudeep,

> -----Original Message-----
> From: Sudeep Holla [mailto:sudeep.holla@....com]
> Sent: Tuesday, May 15, 2018 2:34 AM
> To: Jolly Shah <JOLLYS@...inx.com>; ard.biesheuvel@...aro.org;
> mingo@...nel.org; gregkh@...uxfoundation.org; matt@...eblueprint.co.uk;
> hkallweit1@...il.com; keescook@...omium.org;
> dmitry.torokhov@...il.com; mturquette@...libre.com;
> sboyd@...eaurora.org; michal.simek@...inx.com; robh+dt@...nel.org;
> mark.rutland@....com; linux-clk@...r.kernel.org
> Cc: Sudeep Holla <sudeep.holla@....com>; Rajan Vaja <RAJANV@...inx.com>;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> devicetree@...r.kernel.org
> Subject: Re: [PATCH v6 04/11] firmware: xilinx: Add query data API
> 
> 
> 
> On 14/05/18 20:16, Jolly Shah wrote:
> > HI Sudeep,
> >
> 
> [...]
> 
> >>
> >> Can you give more insight into this ? How will be this used ? How
> >> this aligns with data we get from DT ? I am just trying to understand
> >> how is this information split between this API and DT for example.
> >>
> >
> > This API is used to get clock information from firmware and register
> > clocks accordingly in driver. In our case, firmware maintains database
> > of all clocks available on chip. DT will provide information for off
> > chip reference clocks only. This is to avoid duplication of clocks
> > data in DT and firmware both as firmware anyways need clock data to
> > manage them.
> >
> 
> I wanted to understand the difference with example. What kind of information
> you get from DT and what you get from firmware ?
> 
> --
> Regards,
> Sudeep


Below is an example showing PLL and Leaf clock derivation:

Input ref clocks->Mux->Multiplier/Divider->PLL*
Pll1/pll2/pll3/pll4->Mux->Divider->Gate->Leaf clock1

Here Off chip input ref clock information comes from DT.
Rest information for Pll/leaf clocks come from firmware using query API. For clock driver, query API is used to get topology, flags, parents etc information per clock.

Thanks,
Jolly Shah