[PATCH 6/7] arm: mediatek: enable gpt6 on boot up to make arch timer working

Linus Walleij
2014-08-11T07:15:39Z

On Thu, Jul 31, 2014 at 6:42 PM, Matthias Brugger
<matthias.bgg@gmail.com> wrote:

> We enable GTP6 which ungates the arch timer clock. Apart we write the
> frequency with which the timer is running in the CNTFREQ register.
> In the future this should be done in the bootloader.
>
> Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>
(...)

> + if (of_machine_is_compatible("mediatek,mt6589")) {
> + /* set cntfreq register which is not done in bootloader */
> + asm volatile("mcr p15, 0, %0, c14, c0, 0" : : "r" (13000000));

I guess this is for something like the ARM arch timer in
drivers/clocksource/arm_arch_timer.c

Instead of doing this, use the DT property "clock-frequency" on
the ARM arch timer node, as that overrides the CP15 setting.

> +
> + /* turn on GPT6 which ungates arch timer clocks */
> + gpt_base = ioremap(GPT6_CON_MT65xx, 0x04);
> + }
> +
> + /* enabel clock and set to free-run */
> + if (gpt_base)
> + writel(0x31, gpt_base);

Why is this not done properly in the GPT driver (I guess
in drivers/clocksource/mtk_timer.c) instead of remapping
it and fiddling around in the machine?

If it only affects the mt6589 just add another compatible string
to that driver like "mediatek,mt6589-timer" as it properly reflects the
fact that this timer is slightly different on the 6589.

Also use a #define for the magic constant 0x31.

Yours,
Linus Walleij