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Unable to affect GPIO lines via Linux

I'm trying to get some GPIO signals toggling under Linux.

I've compiled the kernel from https://github.com/koenkooi/linux/tree/linux-ti33x-psp-3.2-r5a+gitr09e9651bcf2ee8d86685f2a8075bc6557b1d3b91.

But /sys/class/gpio fails to work as expected.

I've tested using the Angstrom distro, and all seems fine, so it's not the hardware.

Can I confirm here that I've got all registers setup as they should:-

cm_per_gpio2_clktrl = 0x00000002
conf_gpmc_data0 = 0x0000002f
gpio2_gpio_oe = 0xffffffff

I then write:-

gpio2_gpio_dataout = 0x00000000
gpio2_gpio_dataout = 0xffffffff
gpio2_gpio_dataout = 0x00000000
gpio2_gpio_dataout = 0xffffffff
....

But my scope shows all GPIO pins remain inactive.

Have I missed setting up any other registers ?

Cheers