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:   Wed, 12 Aug 2020 13:09:44 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Amit Pundir <amit.pundir@...aro.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        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>,
        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 8/12/2020 1:05 PM, Amit Pundir wrote:
> Hi Rajendra,
> 
> On Wed, 12 Aug 2020 at 11:18, Rajendra Nayak <rnayak@...eaurora.org> wrote:
>>
>>
>> On 8/12/2020 7:03 AM, John Stultz wrote:
>>> 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.
>>
>> This seems like the same issue that was also reported on venus [1] because the
>> clock frequency tables apparently don;t exactly match the achievable clock
>> frequencies (which we also used to construct the OPP tables)
>>
>> Can you try updating the OPP table for QUP to have 102400000 instead of the
>> current 100000000 and see if that fixes it?
> 
> That worked. Thanks.
> 
> Should this change be common to base sdm845.dtsi or platform specific dts?
> For what it's worth, we see this BT breakage on PocoF1 phone too.

Thanks for confirming, it will have to be part of the SoC dtsi, and I am
guessing a similar change is perhaps also needed on sc7180.
I will send a patch out to fix the OPP tables for both.

> 
> Regards,
> Amit Pundir
> 
> 
>>
>> [1] https://lkml.org/lkml/2020/7/27/507
>>
>>>
>>> thanks
>>> -john
>>>
>>
>> --
>> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
>> of Code Aurora Forum, hosted by The Linux Foundation

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation