[U-Boot] [PATCH] timer: Add High Precision Event Timers (HPET) support

[Simon Glass]

Hi,

On 29 March 2018 at 18:52, Andy Shevchenko
<andriy.shevchenko at linux.intel.com> wrote:
> On Wed, 2018-03-28 at 17:58 -0700, Ivan Gorinov wrote:
>> Adding HPET as an alternative timer for x86 (default is TSC).
>> HPET main counter has constant clock frequency, calibration is not
>> required.
>> This change also makes TSC timer driver optional on x86 platforms.
>> If X86_TSC is disabled, early timer functions are provided by HPET.
>>
>> HPET can be selected as the tick timer in the Device Tree "chosen"
>> node:
>>
>>   /include/ "hpet.dtsi"
>>
>>   chosen {
>>     tick-timer = "/hpet0";
>>   };
>>
>
>
> First question is how this will work in case of Broadwell and Ivybridge
> that have something to do with HPET in their CPU code, i.e.
>
> arch/x86/cpu/broadwell/pch.c
> arch/x86/cpu/ivybridge/lpc.c
>
> ?
>
> Look for
>
>     clrsetbits_le32(RCB_REG(HPTC), 3, 1 << 7);
>
>> +static int hpet_timer_get_count(struct udevice *dev, u64 *count)
>
>> +static int hpet_timer_probe(struct udevice *dev)
>
>> +#ifndef CONFIG_X86_TSC_TIMER
>
>> +#define EARLY_HPET_BASE 0xfed00000
>
> HPET address is fixed, AFAIU, on x86, and provided by config option in
> U-Boot.
>
>> +unsigned long notrace timer_early_get_rate(void)
>
>> +u64 notrace timer_early_get_count(void)
>
>> +int timer_init(void)
>
> These functions have too much code duplication with above.

Perhaps that code can be removed in favour of this driver? I am happy
to test on these platforms if it helps.

Regards,
Simon