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

[Joe.C]

On Tue, 2014-08-12 at 11:02 +0200, Matthias Brugger wrote:
> 2014-08-11 9:15 GMT+02:00 Linus Walleij <linus.walleij at linaro.org>:
> > On Thu, Jul 31, 2014 at 6:42 PM, Matthias Brugger
> > <matthias.bgg at 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 at 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?
> 
> I didn't put it in the GPT driver, because that would mean, that you
> need to have the mtk_timer to be able to use the ARM arch timer.
> From my understanding this are two independent blocks in the SoC.
> Apart from that, as stated in the commit message, this patch is a
> workaround until we have a bootloader which does this for us.
> Therefore I thought the init_time function would be the better place to do this.

Can we have a separate node like mt6577-timerfixup then?
I'm preparing patch for mt8127 and mt8135. They all need this and use
same address and. In current form, I'll have to make this check against
a compatible string array.

Joe.C