linux-kernel - Re: [RFC v2 03/11] tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state

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Date:   Tue, 11 Aug 2020 18:33:36 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Rajendra Nayak <rnayak@...eaurora.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-scsi@...r.kernel.org,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Doug Anderson <dianders@...omium.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-spi@...r.kernel.org, linux-serial@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [RFC v2 03/11] tty: serial: qcom_geni_serial: Use OPP API to set
 clk/perf state

On Tue, Aug 11, 2020 at 4:11 PM John Stultz <john.stultz@...aro.org> wrote:
>
> On Wed, Mar 20, 2019 at 2:49 AM Rajendra Nayak <rnayak@...eaurora.org> wrote:
> >
> > geni serial needs to express a perforamnce state requirement on CX
> > depending on the frequency of the clock rates. Use OPP table from
> > DT to register with OPP framework and use dev_pm_opp_set_rate() to
> > set the clk/perf state.
> >
> > Signed-off-by: Rajendra Nayak <rnayak@...eaurora.org>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > ---
> >  drivers/tty/serial/qcom_geni_serial.c | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> >
>
> Hey,
>   I just wanted to follow up on this patch, as I've bisected it
> (a5819b548af0) down as having broken qca bluetooth on the Dragonboard
> 845c.
>
> I haven't yet had time to debug it yet, but wanted to raise the issue
> in case anyone else has seen similar trouble.

So I dug in a bit further, and this chunk seems to be causing the issue:
> @@ -961,7 +963,7 @@ static void qcom_geni_serial_set_termios(struct uart_port *uport,
>                 goto out_restart_rx;
>
>         uport->uartclk = clk_rate;
> -       clk_set_rate(port->se.clk, clk_rate);
> +       dev_pm_opp_set_rate(port->dev, clk_rate);
>         ser_clk_cfg = SER_CLK_EN;
>         ser_clk_cfg |= clk_div << CLK_DIV_SHFT;
>


With that applied, I see the following errors in dmesg and bluetooth
fails to function:
[    4.763467] qcom_geni_serial 898000.serial: dev_pm_opp_set_rate:
failed to find OPP for freq 102400000 (-34)
[    4.773493] qcom_geni_serial 898000.serial: dev_pm_opp_set_rate:
failed to find OPP for freq 102400000 (-34)

With just that chunk reverted on linus/HEAD, bluetooth seems to work ok.

thanks
-john