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

[Rajendra Nayak]

Hi Matthias,

On 4/9/2020 11:15 PM, Matthias Kaehlcke wrote:
> 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@xxxxxxxxxxxxxx>
> > Cc: Akash Asthana <akashast@xxxxxxxxxxxxxx>
> > Cc: linux-serial@xxxxxxxxxxxxxxx
> > ---
> >   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.

right, looks like I should put some error check there

> 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).

I think I did that initially because I wanted to use that to call into
dev_pm_opp_put_clkname during cleanup. That however never worked since
the way the clk_put is done in dev_pm_opp_put_clkname() and _opp_table_kref_release()
seems buggy. I kind of forgot about fixing it up, I will figure our whats the right
way to do it, and either not call dev_pm_opp_put_clkname() or not store the
opp table returned by it.

thanks for taking time to review.

- Rajendra
 

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