linux-kernel - Re: [PATCH] clk: qcom: gcc-sdm845: Use floor ops for sdcc clks

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Message-ID: <CAD=FV=Vr5o-b86588qe--bVZ5YjKVB3gzaoYa6YcqCd9smkxVg@mail.gmail.com>
Date:   Fri, 30 Aug 2019 14:34:21 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Taniya Das <tdas@...eaurora.org>
Subject: Re: [PATCH] clk: qcom: gcc-sdm845: Use floor ops for sdcc clks

Hi,

On Fri, Aug 30, 2019 at 12:51 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Some MMC cards fail to enumerate properly when inserted into an MMC slot
> on sdm845 devices. This is because the clk ops for qcom clks round the
> frequency up to the nearest rate instead of down to the nearest rate.
> For example, the MMC driver requests a frequency of 52MHz from
> clk_set_rate() but the qcom implementation for these clks rounds 52MHz
> up to the next supported frequency of 100MHz. The MMC driver could be
> modified to request clk rate ranges but for now we can fix this in the
> clk driver by changing the rounding policy for this clk to be round down
> instead of round up.

Since all the MMC rates are expressed as "maximum" clock rates doing
it like you are doing it now seems sane.


> Fixes: 06391eddb60a ("clk: qcom: Add Global Clock controller (GCC) driver for SDM845")
> Reported-by: Douglas Anderson <dianders@...omium.org>
> Cc: Taniya Das <tdas@...eaurora.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>
> I suppose we need to do this for all the sdc clks in qcom driver?

Seems like a good idea to me.


>  drivers/clk/qcom/gcc-sdm845.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Douglas Anderson <dianders@...omium.org>


-Doug