linux-kernel - Re: [PATCH v3 4/6] clk: qcom: clk-rcg2: don't re-search config on rcg2_set

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Date:   Wed, 29 Mar 2023 12:52:23 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Christian Marangi <ansuelsmth@...il.com>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Christian Marangi <ansuelsmth@...il.com>
Subject: Re: [PATCH v3 4/6] clk: qcom: clk-rcg2: don't re-search config on rcg2_set_rate

Quoting Christian Marangi (2023-01-17 05:54:57)
> Currently the rcg2 driver search the rate to apply 2 times.
> - In _freq_tbl_determine_rate for the determine_rate function used by
>   core clk to understand the best rate to set with set_rate
> - In rcg2_set_rate where the suggested rate is not trusted and searched
>   another time using a CEIL or FLOOR policy.
> 
> This is fundamentally wrong as we are ignoring what core clock is
> deciding and just setting whatever clock configuration we want for the
> suggested clock. The problem is in the fact that the correct clock
> should have already be searched and selected with the determine_rate
> function and set_rate should just apply whatever clock was provided.

It sounds like you're assuming the rate coming into the set_rate clk_op
is rounded? Don't make that assumption. The set_rate clk_op should round
the rate again. The parent rate could have changed.