I would like being able to test patches on the Droid 4 without having to carry a development phone around all the time. Testing on my day-to-day phone is not a good idea, since that means being offline during the tests. A simple solution would be to do the testing remotely, which should also allow doing automated tests for KernelCI. Unfortunatley doing this on a phone is a bit harder than on an average development board due to the hardware design.
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Multiple people asked camera related questions during my talk as FOSDEM (and after it). I did some basic reverse engineering, so let me share what I know.
The Droid 4 works with a OMAP4430, which has a imaging subsystem (ISS). It is documented quite well in the datasheet and there is a Linux kernel driver available in staging (omap4iss), which was written by Laurent Pinchart (thanks!). This module provides two MIPI CSI-2 interfaces to connect camera sensors.
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I gave a talk at FOSDEM about the current mainline kernel support for the Droid 4 and its open issues. If you follow this blog you probably already know the information I presented and I’m not a good presenter (sorry!). If you are interested anyways, you can find the recording and my slides on the following here:
Slides Video Recording (mp4) Video Recording (WebM/VP9) Video Recording (Youtube) – Sebastian
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It has been some time since my last post about the Droid 4. 4.13 will most likely be released next week, so let’s have a look at newly added features related to the Droid 4:
crypto acceleration for AES and 3DES support for ISL29030 (proximity and ambient light sensor) USB phy support battery monitoring support bluetooth Unfortunately the list for 4.14 will be a lot shorter (or even empty), since most other submissions are still in review (or need work).
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The 4.12 merge window will most likely close on Sunday, so its a good time to check the Droid 4 status matrix. This merge window lots of changes were queued:
New drivers: real time clock (RTC), power button, analogue digital converter (ADC), battery charger, LEDs (RGB, capslock status, android buttons)
DTS additions: LCD (no driver yet), HDMI, Keyboard/LCD backlight (no driver yet), Touchscreen, Temperature sensor, Accelerometer, Compass, Regulators, RTC, Power button, ADC, USB PHY (no driver yet), Battery charger, LEDs, Keyboard, Poweroff, USB configuration for modems
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Today I had another look at GPS for Droid 4. In theory it has 3 different chips, that have GPS receivers: WL1285C, MDM6600, WG3LTE. The Cyanogenmod changelog for the Droid 4 contains a hint, that WL1285C’s GPS module is the one actually used:
Don't hold st_wakelock until BT/GPS is used for the first time Also the stock kernel contains a driver for GPS from WiLink. WiLink based chips come with either SPI or SDIO connection for WLAN and a shared UART for Bluetooth (BT), FM radio, GPS and NFC.
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Some time has gone by since my last post, so lets have a look what changed for Droid 4:
I prepared a CPCAP LED driver I published updated patches for the N950 display (also used for D4) Milo Kim published TI LMU backlight driver supporting D4’s LM3532 Tony published a CPCAP ADC driver Tony published a simple CPCAP battery charer driver Tony published CPCAP usb phy Tony published Motorola MDM6600 patch for qmi_wwan Tony published lots of droid 4 DTS patches adding Touchscreen LCD backlight GPIO poweroff Temperature sensor HDMI support (incl.
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Today I had a first look at the modems of the Droid 4. Conclusion Modem 1 (2G/3G): Name: MDM 6600 USB ID: 22b8:2a70 Drivers: bpwake - wakeup ttyO0 via gpio mdm6600_ctrl - modem gpio control via sysfs mdm6600_modem - usb-serial driver (unused?) qcusbnet - qmi driver, mainline provides alternative ts27010mux - 3GPP 27.010 mux ldisc for ttyO0 Modem 2 (4G) Name: W3GLTE USB ID: 22b8:4267 Drivers: wrigley_ctrl - modem gpio control via sysfs oob-wake - usb wakeup via gpio cdc-ether - usb network device Both modems require a GPIO control driver for powering them up/down.
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With Debian up & running I had a look at what needs to be done in the mainline kernel. Tony is working on the ADC parts, which are required for the battery/charger work and mentioned he will have a look at USB. He also mentioned, that somebody with spare cycles could take care of CPCAP’s rtc & watchdog. I had a look at Motorola’s vendor kernel and as far as I can see CPCAP does not come with a watchdog (unlike twl4030/twl6040).
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In the last post I rooted the Droid 4 and installed LineageOS with SafeStrap as bootloader. Today I took care of getting the mainline kernel running and preparing a rootfs.
After some communication with Tony I got the kexec stuff running (at the end the problem was my compiler generating binaries not suitable for Android). Instead of getting a compiler toolchain for Android I decided to rewrite the binary into a shellscript, so that no compiler is required.
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