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

Matthias Brugger
2014-08-14T09:35:56Z

2014-08-14 4:24 GMT+02:00 Joe.C <srv_yingjoe.chen@mediatek.com>:
> On Tue, 2014-08-12 at 11:02 +0200, Matthias Brugger wrote:
>> 2014-08-11 9:15 GMT+02:00 Linus Walleij <linus.walleij@linaro.org>:
>> > 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?
>>
>> 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.

The way to go is to add another of_machine_is_compatible for every
SoC. If the address is the same just use logical or.

Cheers,
Matthias

>
> Joe.C
>
>

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