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

Rajendra Nayak
2020-04-13T13:58:53Z

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@codeaurora.org>
>> Cc: Akash Asthana <akashast@codeaurora.org>
>> Cc: linux-serial@vger.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.

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