linux-kernel - Re: [PATCH 02/21] tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state

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Date:   Mon, 13 Apr 2020 19:43:16 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Akash Asthana <akashast@...eaurora.org>, viresh.kumar@...aro.org,
        sboyd@...nel.org, bjorn.andersson@...aro.org, agross@...nel.org
Cc:     linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH 02/21] tty: serial: qcom_geni_serial: Use OPP API to set
 clk/perf state

[]..

>> @@ -1318,13 +1321,16 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>>       if (of_property_read_bool(pdev->dev.of_node, "cts-rts-swap"))
>>           port->cts_rts_swap = true;
>> +    port->se.opp = dev_pm_opp_set_clkname(&pdev->dev, "se");
>> +    dev_pm_opp_of_add_table(&pdev->dev);
>> +
>>       uport->private_data = drv;
>>       platform_set_drvdata(pdev, port);
>>       port->handle_rx = console ? handle_rx_console : handle_rx_uart;
>>       ret = uart_add_one_port(drv, uport);
>>       if (ret)
>> -        return ret;
>> +        goto err;
>>       irq_set_status_flags(uport->irq, IRQ_NOAUTOEN);
>>       ret = devm_request_irq(uport->dev, uport->irq, qcom_geni_serial_isr,
>> @@ -1332,7 +1338,7 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>>       if (ret) {
>>           dev_err(uport->dev, "Failed to get IRQ ret %d\n", ret);
>>           uart_remove_one_port(drv, uport);
>> -        return ret;
>> +        goto err;
>>       }
>>       /*
>> @@ -1349,11 +1355,14 @@ static int qcom_geni_serial_probe(struct platform_device *pdev)
>>           if (ret) {
>>               device_init_wakeup(&pdev->dev, false);
>>               uart_remove_one_port(drv, uport);
>> -            return ret;
>> +            goto err;
>>           }
>>       }
>>       return 0;
>> +err:
>> +    dev_pm_opp_of_remove_table(&pdev->dev);
> do we need to call "dev_pm_opp_put_clkname" here and in remove to release clk resource grabbed by
> 
> dev_pm_opp_set_clkname(&pdev->dev, "se");?

Thanks for catching this, I did indeed try to call dev_pm_opp_put_clkname() but the way clk_put
is handled in it seems buggy. I need to go back and fix it. Besides I realized dev_pm_opp_of_remove_table()
does go ahead and do a clk_put on the clock.

Viresh, whats the right way to clean up

>> +    port->se.opp = dev_pm_opp_set_clkname(&pdev->dev, "se");
>> +    dev_pm_opp_of_add_table(&pdev->dev);

is it
1. dev_pm_opp_of_remove_table()
    dev_pm_opp_put_clkname()

or
2. dev_pm_opp_put_clkname()
    dev_pm_opp_of_remove_table()

or, what this patch is currently doing, which is just calling dev_pm_opp_of_remove_table()?

Note that both 1. and 2. today result in a crash, since they don't handle clk_put very well.
I can send in a fix if you think dev_pm_opp_put_clkname is needed and in a certain order.

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