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

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Message-ID: <20200417180041.GD199755@google.com>
Date:   Fri, 17 Apr 2020 11:00:41 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajendra Nayak <rnayak@...eaurora.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

Hi Rajendra,

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.

>  };
>  
>  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.").

> 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.