linux-kernel - Re: [PATCH 1/2] clk: qcom: gcc-sc7180: Use floor ops for sdcc clks

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Message-ID: <160763203722.1580929.17813582697140984791@swboyd.mtv.corp.google.com>
Date:   Thu, 10 Dec 2020 12:27:17 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Taniya Das <tdas@...eaurora.org>, vbadigan@...eaurora.org,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] clk: qcom: gcc-sc7180: Use floor ops for sdcc clks

Quoting Douglas Anderson (2020-12-10 10:22:38)
> I would repeat the same commit message that was in commit 5e4b7e82d497
> ("clk: qcom: gcc-sdm845: Use floor ops for sdcc clks") but it seems
> silly to do so when you could just go read that commit.
> 
> NOTE: this is actually extra terrible because we're missing the 50 MHz
> rate in the table (see the next patch AKA ("clk: qcom: gcc-sc7180: Add
> 50 MHz clock rate for SDC2")).  That means then when you run an older
> SD card it'll try to clock it at 100 MHz when it's only specced to run
> at 50 MHz max.  As you can probably guess that doesn't work super
> well.
> 
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Fixes: 17269568f726 ("clk: qcom: Add Global Clock controller (GCC) driver for SC7180")
> ---
> Taniya: can you please update whatever process is used to generate
> these clock files to use floor for SD card clocks.  I hope you can
> also scour through these files looking for similar problems on other
> SoCs and submit patches for them.

Any chance the consumer of this clk can call clk_round_rate() and WARN()
if the rate is not anywhere near what it wants it to be? I fear that
this problem will just keep coming up otherwise.