Patch for Maemo Linux Kernel (v2.6.21)

Felix Xiaozhu Lin

Previously, if you want to keep N810's serial port always on, there was no perfect kernel.

  • With Nokia's official Mameo kernel (2.6.21), the system cannot fall into deep sleep state when the UART is enabled (Power: ~80mA @ 3.8V).
  • Linux-omap kernel (>2.6.26) can manage UART's power state. However, it incurs high system idle power (~30mA @ 3.8 V), even when UART is disabled.

    • To address such a issue, I backport UART pm from linux-omap 2.6.28 to Maemo kernel, and create this patch.
    Though ugly, it successfully reduces system idle power to <10mA @ 3.8V.

    Though still not so perfect comparing with the "ideal case" (Maemo kernel: idle power when UART is disabled (<2mA @ 3.8V)),
    I think it is good enough as a research platform.
    Maybe I will figure out how to cut off the rest part of idle power. Or maybe it is the necessary cost to keep UART on.

    Will be released soon.