The enforced open drain problem appears after connecting the PCA9685 #1381

roxanaluca · 2020-04-28T17:13:39Z

Describe the bug
I have connected PCA9685 and Arducam Multi Camera Adapter on Raspberry Pi. The first pin supplies 3.3V on Arducam Adapter, and at the same time the PCA9685 motor driver. The Raspberry Pi detect the PCA9685 connection via detect -y 3.
To reproduce
Adding a new bus 3 in /boot/config in config.txt
start_x=1
gpu_mem=128
dtparam=i2c_arm=on
dtoverlay=i2c-gpio,bus=3,i2c_gpio_delay_us=1,i2c_gpio_sda=16,i2c_gpio_scl=26

Expected behaviour
The error should not happen because I measured the voltage in Raspberry and the PCA9685. I follow the Adafruit guideline.

Actual behaviour
It is possible that the servo motors wouldn't work properly.

System

Which model of Raspberry Pi? Pi3B+
Which OS and version (cat /etc/rpi-issue)?
Generated using pi-gen, https://github.com/RPi-Distro/pi-gen, 150e25c4f8123a4c9c63e8dca1b4737fa6c1135c, stage5
Which firmware version (vcgencmd version)?
Feb 12 2020 12:39:27
Copyright (c) 2012 Broadcom
version 53a54c770c493957d99bf49762dfabc4eee00e45 (clean) (release) (start_x)
Which kernel version (uname -a)?
Linux raspberrypi 4.19.97-v7+ No sound on HDMI or headphone jack except hello_audio #1294 SMP Thu Jan 30 13:15:58 GMT 2020 armv7l GNU/Linux

Logs
dmesg | grep i2c
[ 3.033396] i2c /dev entries driver
[ 4.707228] gpio-16 (3.i2c): enforced open drain please flag it properly in DT/ACPI DSDT/board file
[ 4.707308] gpio-26 (3.i2c): enforced open drain please flag it properly in DT/ACPI DSDT/board file
[ 4.707769] i2c-gpio 3.i2c: using lines 16 (SDA) and 26 (SCL)

The text was updated successfully, but these errors were encountered:

roxanaluca · 2020-05-01T15:19:12Z

I put pull up resistances between SDA and SCL pins and it doesn't work.
Please let me know what to do.
Many thanks

pelwell · 2020-05-01T16:41:28Z

The Pi GPIO pins don't have an "open drain" mode - they do outputs and inputs (and the alternate functions). What you are seeing is a warning about what something sees as an invalid or incomplete configuration in Device Tree, rather than a real problem with the hardware. I'll try to understand the issue to see if we can avoid the warning, but until then I don't think there is any chance of you damaging the servo motor as a result of the "problem" that causes the message.

pelwell · 2020-05-01T16:44:33Z

You do, however, need pull-ups on any I2C bus. Pis have built-in 1K8 pullups on the hardware I2C buses.

Is the servo motor not working for you? I didn't understand that from your original report - I thought you were suggesting a possible problem rather than an actual one.

roxanaluca · 2020-05-01T17:41:22Z

The servo motors are working properly. I was worried about this problem.

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

pelwell · 2020-05-02T13:04:25Z

The i2c-gpio overlay has been updated to avoid the alarming warnings. This does not change the functionality at all. The change is in our Linux kernel source repo, and will appear later in the Raspbian kernel package when it is next rebuilt.

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

kernel: vc4_hdmi: Add CEC support for 2711 See: raspberrypi/linux#3601 kernel: overlays: Move fixed-clock nodes to the root See: raspberrypi/linux#3607 kernel: bcm2835_isp fixes for constness See: raspberrypi/linux#3592 kernel: video: bcm2708_fb: Disable FB if no displays found See: raspberrypi/linux#3598 kernel: vc4_hdmi_phy: Fix typo in phy_get_cp_current See: raspberrypi/linux#3594 kernel: configs: Add missing TOUCHSCREEN_RASPBERRYPI_FW=m See: Hexxeh/rpi-firmware#223 kernel: configs: Add missing PPS configs See: raspberrypi/linux#3593 kernel: overlays: gpio-keys: Avoid open-drain warnings See: #1381 kernel: overlays: Make the i2c-gpio overlay safe again kernel: ARM: dts: bcm2711: Allow 40-bit DMA for SPI See: raspberrypi/linux#3570 firmware: In KMS mode, prevent use of the firmware rotations firmware: power: Adjust ARM:AXI divider ratio if ARM freq > 1500 MHz firmware: imx477: Remove STILLS flag from 720p mode userland: tvservice: Fix freeze on old firmware

kernel: vc4_hdmi: Add CEC support for 2711 See: raspberrypi/linux#3601 kernel: overlays: Move fixed-clock nodes to the root See: raspberrypi/linux#3607 kernel: bcm2835_isp fixes for constness See: raspberrypi/linux#3592 kernel: video: bcm2708_fb: Disable FB if no displays found See: raspberrypi/linux#3598 kernel: vc4_hdmi_phy: Fix typo in phy_get_cp_current See: raspberrypi/linux#3594 kernel: configs: Add missing TOUCHSCREEN_RASPBERRYPI_FW=m See: #223 kernel: configs: Add missing PPS configs See: raspberrypi/linux#3593 kernel: overlays: gpio-keys: Avoid open-drain warnings See: raspberrypi/firmware#1381 kernel: overlays: Make the i2c-gpio overlay safe again kernel: ARM: dts: bcm2711: Allow 40-bit DMA for SPI See: raspberrypi/linux#3570 firmware: In KMS mode, prevent use of the firmware rotations firmware: power: Adjust ARM:AXI divider ratio if ARM freq > 1500 MHz firmware: imx477: Remove STILLS flag from 720p mode userland: tvservice: Fix freeze on old firmware

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but gpiolib can emulate it in software if configured correctly. Silence the warning by declaring the GPIOs as requiring open-drain mode, trusting gpiolib to manage the emulation. The previous incarnation of this patch took the other approach of telling the i2c-gpio driver that the GPIOs were configured for open-drain, but this had the effect of disabling the emulation. In some cases this appears to work, but examining the waveforms as analogue voltages shows contention, the success or failure depending on drive strengths. See: raspberrypi/firmware#1381 See: raspberrypi/firmware#1401 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

Source: kernel.org MR: 103889 Type: Enhancement Disposition: Merged from https://github.com/raspberrypi/linux.git rpi-5.4.y ChangeID: ae10c15867d9a5b85eefaf11333bd30473af4b2b Description: The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com> Signed-off-by: Corey Minyard <cminyard@mvista.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but gpiolib can emulate it in software if configured correctly. Silence the warning by declaring the GPIOs as requiring open-drain mode, trusting gpiolib to manage the emulation. The previous incarnation of this patch took the other approach of telling the i2c-gpio driver that the GPIOs were configured for open-drain, but this had the effect of disabling the emulation. In some cases this appears to work, but examining the waveforms as analogue voltages shows contention, the success or failure depending on drive strengths. See: raspberrypi/firmware#1381 See: raspberrypi/firmware#1401 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but gpiolib can emulate it in software if configured correctly. Silence the warning by declaring the GPIOs as requiring open-drain mode, trusting gpiolib to manage the emulation. The previous incarnation of this patch took the other approach of telling the i2c-gpio driver that the GPIOs were configured for open-drain, but this had the effect of disabling the emulation. In some cases this appears to work, but examining the waveforms as analogue voltages shows contention, the success or failure depending on drive strengths. See: raspberrypi/firmware#1381 See: raspberrypi/firmware#1401 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but i2c-gpio works anyway. Silence the warning by declaring that open-drain mode has been enabled by other means. See: raspberrypi/firmware#1381 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

The i2c-gpio driver expects to use a GPIO in open-drain mode. Failure to configure it in that way causes alarming warnings in the kernel log. The BCM283x and BCM2711 GPIO blocks don't support open-drain mode, but gpiolib can emulate it in software if configured correctly. Silence the warning by declaring the GPIOs as requiring open-drain mode, trusting gpiolib to manage the emulation. The previous incarnation of this patch took the other approach of telling the i2c-gpio driver that the GPIOs were configured for open-drain, but this had the effect of disabling the emulation. In some cases this appears to work, but examining the waveforms as analogue voltages shows contention, the success or failure depending on drive strengths. See: raspberrypi/firmware#1381 See: raspberrypi/firmware#1401 Signed-off-by: Phil Elwell <phil@raspberrypi.com>

kernel: vc4: cec: Restore cec physical address on reconnect See: raspberrypi/linux#3655 kernel: snd_bcm2835: disable HDMI audio when vc4 is used See: raspberrypi/linux#3640 kernel: Enhanced w1_therm Linux Kernel Module See: raspberrypi/linux#3540 kernel: overlays: Update upstream overlays after vc4-kms-v3d change kernel: overlays: i2c-gpio: Avoid open-drain warnings See: #1381 See: #1401 kernel: staging: vchiq_arm: Use g_dma_dev for dma_unmap_sg See: raspberrypi/linux#3647 firmware: arm_ldconfig: Don't pad initramfs files See: #1395

kernel: vc4: cec: Restore cec physical address on reconnect See: raspberrypi/linux#3655 kernel: snd_bcm2835: disable HDMI audio when vc4 is used See: raspberrypi/linux#3640 kernel: Enhanced w1_therm Linux Kernel Module See: raspberrypi/linux#3540 kernel: overlays: Update upstream overlays after vc4-kms-v3d change kernel: overlays: i2c-gpio: Avoid open-drain warnings See: raspberrypi/firmware#1381 See: raspberrypi/firmware#1401 kernel: staging: vchiq_arm: Use g_dma_dev for dma_unmap_sg See: raspberrypi/linux#3647 firmware: arm_ldconfig: Don't pad initramfs files See: raspberrypi/firmware#1395