linux-kernel - Re: [PATCH v2 01/17] tty: serial: qcom_geni_serial: Use OPP API to set clk/perf state

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Date:   Sat, 18 Apr 2020 13:35:56 +0530
From:   Rajendra Nayak <rnayak@...eaurora.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     viresh.kumar@...aro.org, sboyd@...nel.org,
        bjorn.andersson@...aro.org, agross@...nel.org,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Akash Asthana <akashast@...eaurora.org>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH v2 01/17] tty: serial: qcom_geni_serial: Use OPP API to
 set clk/perf state


On 4/17/2020 11:30 PM, Matthias Kaehlcke wrote:
> Hi Rajendra,

Hey Matthias,

> 
> On Fri, Apr 17, 2020 at 07:34:23PM +0530, Rajendra Nayak wrote:
>> geni serial needs to express a perforamnce state requirement on CX
>> powerdomain 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>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: Akash Asthana <akashast@...eaurora.org>
>> Cc: linux-serial@...r.kernel.org
>> ---
>>   drivers/tty/serial/qcom_geni_serial.c | 30 +++++++++++++++++++++++++-----
>>   include/linux/qcom-geni-se.h          |  2 ++
>>   2 files changed, 27 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
>> index 6119090..151012c 100644
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -9,6 +9,7 @@
>>   #include <linux/module.h>
>>   #include <linux/of.h>
>>   #include <linux/of_device.h>
>> +#include <linux/pm_opp.h>
>>   #include <linux/platform_device.h>
>>   #include <linux/pm_runtime.h>
>>   #include <linux/pm_wakeirq.h>
>> @@ -128,6 +129,7 @@ struct qcom_geni_serial_port {
>>   	int wakeup_irq;
>>   	bool rx_tx_swap;
>>   	bool cts_rts_swap;
>> +	bool opp_table;
> 
> The name of the variable suggests that it holds a OPP table, something
> like 'has_opp_table' would be clearer.

I agree with your suggestions, I will update the variable names when I respin.

> 
>>   };
>>   
>>   static const struct uart_ops qcom_geni_console_pops;
>> @@ -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(uport->dev, clk_rate);
>>   	ser_clk_cfg = SER_CLK_EN;
>>   	ser_clk_cfg |= clk_div << CLK_DIV_SHFT;
>>   
>> @@ -1198,8 +1200,11 @@ static void qcom_geni_serial_pm(struct uart_port *uport,
>>   	if (new_state == UART_PM_STATE_ON && old_state == UART_PM_STATE_OFF)
>>   		geni_se_resources_on(&port->se);
>>   	else if (new_state == UART_PM_STATE_OFF &&
>> -			old_state == UART_PM_STATE_ON)
>> +			old_state == UART_PM_STATE_ON) {
>> +		/* Drop the performance state vote */
>> +		dev_pm_opp_set_rate(uport->dev, 0);
>>   		geni_se_resources_off(&port->se);
>> +	}
>>   }
>>   
>>   static const struct uart_ops qcom_geni_console_pops = {
>> @@ -1318,13 +1323,20 @@ 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");
>> +	if (IS_ERR(port->se.opp))
>> +		return PTR_ERR(port->se.opp);
>> +	/* OPP table is optional */
>> +	if (!dev_pm_opp_of_add_table(&pdev->dev))
> 
> Even if the OPP table is optional you probably want to fail if the error
> is anything other than -ENODEV ("'operating-points' property is not found
> or is invalid data in device node.").

sounds valid. I will fix it up and respin. Will just wait a few days to see if
I get any more reviews and feedback.

> 
>> diff --git a/include/linux/qcom-geni-se.h b/include/linux/qcom-geni-se.h
>> index dd46494..737e713 100644
>> --- a/include/linux/qcom-geni-se.h
>> +++ b/include/linux/qcom-geni-se.h
>> @@ -24,6 +24,7 @@ enum geni_se_protocol_type {
>>   
>>   struct geni_wrapper;
>>   struct clk;
>> +struct opp_table;
>>   
>>   /**
>>    * struct geni_se - GENI Serial Engine
>> @@ -39,6 +40,7 @@ struct geni_se {
>>   	struct device *dev;
>>   	struct geni_wrapper *wrapper;
>>   	struct clk *clk;
>> +	struct opp_table *opp;
> 
> This name suggests that the variable holds a single OPP ('struct
> dev_pm_opp'). Most other code uses the name 'opp_table', which
> also seems a good candidate here.

Agree, thanks again for taking time to review.

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