Hello Michal,

On Fri, Nov 23, 2018 at 03:15:11PM +0000, Vokáč Michal wrote:

On 22.11.2018 20:03, Uwe Kleine-König wrote:

quoted

On Thu, Nov 22, 2018 at 04:46:39PM +0000, Vokáč Michal wrote:

quoted

On 22.11.2018 17:23, Uwe Kleine-König wrote:

quoted

So I'd expect this to really work on i.MX6 but not the earlier SoCs
without a gpio specifier.

Maybe you would expect it to work but I already tested and measured
that weeks ago ;) It did not work.

Which pin/gpio do we talk about? Which i.MX6 variant did you test this
on? (Assuming i.MX6D or i.MX6Q and PAD_DISP0_DATA09, did you try setting

	IOMUXC_SW_MUX_CTL_PAD_DISP0_DATA09 (0x020E0194) = 0x00000005
	IOMUXC_SW_PAD_CTL_PAD_DISP0_DATA09 (0x020E04A8) = 0x0000b080

and then play with GPIO 4.30 direction and output value?)

My test setup is as follows:
- SoC is i.MX6DL or i.MX6S - I have three board variants in total.
- Pin used for PWM/GPIO is PAD_GPIO9.
- The pin is not connected to any circuit. Just a test point.
- pinctrl setup in DT:
   - for "pwm":
     - fsl,pins = <MX6QDL_PAD_GPIO_9__PWM1_OUT 0x8>
     - IOMUXC_SW_MUX_CTL_PAD_GPIO09 = 0x00000004
     - IOMUXC_SW_PAD_CTL_PAD_GPIO09 = 0x00000008

   - for "gpio":
    - fsl,pins = <MX6QDL_PAD_GPIO_9__GPIO1_IO09 0xb000>
    - IOMUXC_SW_MUX_CTL_PAD_GPIO09 = 0x00000005
    - IOMUXC_SW_PAD_CTL_PAD_GPIO09 = 0x0000b000

FTR: I suggested 0x0000b080 here, but 0x0000b000 is just fine.

Test scenario:

- In bootloader configure the pin as GPIO output, set it LOW (0V).
   I set it LOW to start in the oposite state than I want to end up in.
- Boot Linux
- Use sysfs to configure the PWM to produce some signal.
- In the PWM driver select the "pwm" pinctrl state.
- Measure the output - expected waveform on the scope.
- Use sysfs to stop the PWM "echo 0 > /sys/class/pwm/pwmchip0/pwm0/enable°
- In the PWM driver select the "gpio" pinctrl state.
- Then in the PWM driver:

a) non-working variant
- Do not request the GPIO - so do not touch its pad control reg.
   It is set as output from the bootloader, data register = 0.
- Measure voltage on the output
   - against GND = 0V
   - against VCC = 0V
- Measure resistance against VCC: Hi-Z

The pin is in Hi-Z mode. That is fine but that does not satisfy any
logic level.

b) working variant
- Request the GPIO, configure it as input.
- Measure voltage on the output
   - against GND = VCC (3.3V)
   - against VCC = 0V
- Measure resistance against VCC = 91.1kOhm

The pull-up is active.

Thanks for your detailed test. So DSE = 0 doesn't work as I (and I think
Lothar) expected.

@Lothar: if Michal did something different than you expected, please
tell us with a few more details.

I can repeat the results on both i.MX6DL and i.MX6S on pwm1 and pwm4.
All pull-up and pull-down combinations gave me the expected results
only if the pin is configured as input. So if I repeat the test and
do not touch the pin in bootloader at all, it works as well even if
I do not request/configure the GPIO in the PWM driver.

OK.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |