linux-kernel - Re: [PATCH 1/3] clk: qcom: smd-rpm: Add rate hooks for clk_smd_rpm_branch

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Date:   Wed, 15 Sep 2021 23:12:37 +0800
From:   Shawn Guo <shawn.guo@...aro.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Loic Poulain <loic.poulain@...aro.org>,
        devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] clk: qcom: smd-rpm: Add rate hooks for
 clk_smd_rpm_branch_ops

On Tue, Sep 14, 2021 at 07:55:21PM -0700, Bjorn Andersson wrote:
> On Mon 13 Sep 19:55 PDT 2021, Shawn Guo wrote:
> 
> > On QCM2290 platform, the clock xo_board runs at 38400000, while the
> > child clock bi_tcxo needs to run at 19200000.  That said,
> > clk_smd_rpm_branch_ops needs the capability of setting rate. Add rate
> > hooks into clk_smd_rpm_branch_ops to make it possible.
> > 
> 
> Most platforms has a crystal oscillator ticking at 38.4MHz feeding the
> PMIC (represented by the rpmcc and its "xo" parent) and out comes the
> bi_tcxo with a fixed 19.2MHz rate.

Yeah, but all those platforms are running clk-rpmh driver, I think.

> Is there a problem with the way sdm660_bi_tcxo is defined in this
> regard?

There is no problem if xo clock is 19.2MHz, but for platforms with
38.4MHz xo, bi_tcxo will be seen as 38.4MHz in clock tree, while we
expect it to be 19.2MHz.

Shawn