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Subject: Re: [PATCH 1/3] clk: qcom: smd-rpm: Add rate hooks for clk_smd_rpm_branch_ops
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Loic Poulain <loic.poulain@linaro.org>,
        devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
        Shawn Guo <shawn.guo@linaro.org>
To:     Shawn Guo <shawn.guo@linaro.org>
Date:   Tue, 14 Sep 2021 14:56:28 -0700
Message-ID: <163165658855.763609.14080313241484048687@swboyd.mtv.corp.google.com>
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Quoting Shawn Guo (2021-09-13 19:55:52)
> 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.

This doesn't sound right. The branch is a simple on/off. If xo_board is
38.4MHz, then there is an internal divider in the SoC that makes bi_tcxo
(i.e. the root of the entire clk tree) be 19.2MHz. We don't model the
divider, I guess because it isn't very important to. Instead, we tack on
a divider field and implement recalc_rate op. See clk-rpmh.c in the qcom
directory for this.