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

[Rob Herring <robherring2@gmail.com>]

On Tue, Aug 12, 2014 at 4:02 AM, Matthias Brugger
<matthias.bgg@gmail.com> 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.

I agree that the bootloader is the right place, and the fixup in the
machine code until that is in place is the right place for the fixup.

Rob