It appears that blue disk leds are not blinking in mainline kernels (tried 2.6.26). To fix that, you'll need to change GPIO setting in drivers/ata/sata_mv.c:

static void mv6_enable_leds(struct mv_host_priv *hpriv, void __iomem *mmio)
{
#if 0 
	writel(0x00000060, mmio + MV_GPIO_PORT_CTL_OFS);
#else 
	writel(0x00000050, mmio + MV_GPIO_PORT_CTL_OFS);
#endif
}

Code has been commited in linux-2.6 main git tree as seen here http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a88656553d18c324554855fccc730c9644048111. So LED will soon be controllable from userland. Expected in 2.6.31

discussion with Erik Benada explaining that :

with conversion of Orion architecture to gpiolib it is now possible to
turn off power LED blinking from userspace - eg. after booting is
finished. You can also turn on power LED blinking before you shut down the system to let user know system is going down.

To turn off power LED blinking after booting is finished:
           echo 1 > /sys/class/gpio/gpio3/value

To turn on power LED blinking before shutdown/reboot:
        echo 1 > /sys/class/gpio/gpio4/value

Disk access leds still don't work properly in 2.6.32… Following code configures SATA gpio, not ARM gpio

writel(0x00000050, mmio + MV_GPIO_PORT_CTL_OFS);