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

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Date:   Thu, 9 Apr 2020 10:45:11 -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,
        Akash Asthana <akashast@...eaurora.org>,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH 02/21] tty: serial: qcom_geni_serial: Use OPP API to set
 clk/perf state

Hi Rajendra,

On Wed, Apr 08, 2020 at 07:16:28PM +0530, Rajendra Nayak 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>
> Cc: Akash Asthana <akashast@...eaurora.org>
> Cc: linux-serial@...r.kernel.org
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 20 +++++++++++++++-----
>  include/linux/qcom-geni-se.h          |  2 ++
>  2 files changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
> index 6119090..754eaf6 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>
> @@ -961,7 +962,7 @@ 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 +1199,10 @@ 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) {
> +		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 +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_set_clkname() can fail for multiple reasons, it seems an error
check would be warranted.

Is it actually necessary to save the OPP table in 'struct geni_se'? Both
the serial and the SPI driver save the table, but don't use it later (nor
does the SE driver).