We have lacked the support for any pinmuxing in U-Boot for Merrifield. A need for pinmuxing some pins has arisen from the fact the I2C#6 is shared with I2C#8 on Merrifield. The latter is not easily accessible because it's a part of a separate MCU we don't have easy access to.
I2C#6 can be and should be made use of in Linux but couldn't because it was blocked by the SCU.
The proposed change is to implement a minimalistic pinctrl driver that reads the configuration off a device tree blob and configures the pins accordingly.
The driver needs some changes to SCU API and thus the addition of scu_ipc_raw_command().
Andy Shevchenko has been helping me by making a prior review and made a lot of suggestions about the general approach that should be taken.
He should also be given credit for the initial kernel code that I have taken as a reference.
The code has been tested on 5 different Edisons on Intel Edison Breakout board and a couple of custom Emlid PCBs by booting a kernel and issuing a i2cdetect -r -y 6 and then loading a driver that made use of the bus.
I also created a Gist on Github with a lot of relevant information like
- output of `acpidump -o tables.dat` - dmesg - output of `grep -H 15 /sys/bus/acpi/devices/*/status` - cat /sys/kernel/debug/gpio - cat /sys/kernel/debug/pinctrl/INTC1002:00/pins - output of `i2cdetect -y -r 6` w/ and w/o external device on the bus
Here it is: https://gist.github.com/staroselskii/097808e05fd609dbafd4fe5ebd618708
Georgii Staroselskii (4): x86: cpu: introduce scu_ipc_raw_command() x86: tangier: pinmux: add API to configure protected pins x86: dts: edison: configure I2C#6 pins x86: tangier: acpi: add I2C6 node
arch/x86/cpu/tangier/Makefile | 2 +- arch/x86/cpu/tangier/pinmux.c | 188 +++++++++++++++++++++ arch/x86/dts/edison.dts | 22 +++ .../include/asm/arch-tangier/acpi/southcluster.asl | 10 ++ arch/x86/include/asm/scu.h | 4 + arch/x86/lib/scu.c | 35 ++++ 6 files changed, 260 insertions(+), 1 deletion(-) create mode 100644 arch/x86/cpu/tangier/pinmux.c