Hi, Tarmo Kuuse <tarmo.ku...@gmail.com> 於 2018年12月27日 週四 下午10:51寫道：
<snip> > Pin is muxed as GPIO and has value 1, but it's still configured as input: > conf_gpmc_a1 = 0x27 > GPIO_OE = 0xFE1FFFFF > GPIO_DATAOUT = 0x820000 > Output voltage = 0.58 V > > # gpioinfo gpiochip1 > gpiochip1 - 32 lines: > ... > line 17: "GPMC_A1" unused output active-high > > This is not OK - pin should be configured as an output in the GPIO_OE > register and it should have a voltage of around 3.3 V. This issue looks similar to this one [1], could you confirm it? Thanks. [1] https://github.com/brgl/libgpiod/issues/32 SZ > > 3. Attempting to set gpio1[17] to low, failure > > # gpioset gpiochip1 17=0 > # echo $? > 0 > > Pin is muxed as GPIO and has value 0, but is configured as an input: > conf_gpmc_a1 = 0x27 > GPIO_OE = 0xFE1FFFFF > GPIO_DATAOUT = 0x800000 > Output voltage = 0.58 V > > This is not OK either - pin should be an output and have a voltage of around > 0 V. > > 4. Verification using sysfs, success > > To compare and contrast, I exported the pin and set it high using the > "deprecated" sysfs interface: > > # echo 49 > /sys/class/gpio/export > # echo high > /sys/class/gpio/gpio49/direction > > Pin is muxed as GPIO, configured as output and has the value 1: > conf_gpmc_a1 = 0x27 > GPIO_OE = 0xFE1DFFFF > GPIO_DATAOUT = 0x820000 > Output voltage = 3.36 V > > This is the expected result - GPIO_OE has output enabled for pin 17 and the > output is 3.36 V. > I also looked at the gpioinfo for this test: > > # gpioinfo gpiochip1 > gpiochip1 - 32 lines: > ... > line 17: "GPMC_A1" "sysfs" output active-high [used] > > It looks to me that libgpiod "gpioset" does not enable the pin as output in > GPIO_OE register. This register is described in section "25.4.1.16 GPIO_OE > Register (offset = 134h) [reset = FFFFFFFFh]" of "AM335x and AMIC110 Sitara > Processors Technical Reference Manual Rev. P" from > http://www.ti.com/lit/pdf/spruh73. > > I have also tried writing a small C program directly against the kernel's > "linux/gpio.h" API to achieve the same result as gpioset does. It fails in > the same way as gpioset does. > > === Environment and hardware details === > > Hardware: BeagleCore BCM.ETR1 (compatible with a Beaglebone Black rev C) > CPU: Texas Instruments AM3358BZCZA100 (armv7l) > Debian: Buster/10 (BeagleBoard.org Debian Image 2018-12-10 from > https://rcn-ee.net/rootfs/bb.org/testing/2018-12-10/buster-iot/bone-debian-buster-iot-armhf-2018-12-10-4gb.img.xz) > Kernel: ver 4.14.79-ti-r86 > libgpiod and gpiod packages: ver 1.2-3 > > > -- System Information: > Debian Release: buster/sid > APT prefers testing > APT policy: (500, 'testing') > Architecture: armhf (armv7l) > > Kernel: Linux 4.14.79-ti-r86 (SMP w/1 CPU core; PREEMPT) > Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE=C.UTF-8 > (charmap=UTF-8) > Shell: /bin/sh linked to /bin/dash > Init: systemd (via /run/systemd/system) > > Versions of packages libgpiod2 depends on: > ii libc6 2.28-2 > ii libgcc1 1:8.2.0-13 > ii libstdc++6 8.2.0-13 > > libgpiod2 recommends no packages. > > libgpiod2 suggests no packages. > > -- no debconf information
