Re: [U-Boot] [PATCH v2] timer: add High Precision Event Timers (HPET) support

On Fri, Mar 30, 2018 at 1:29 AM, Ivan Gorinov ivan.gorinov@intel.com wrote:

Adding HPET as an alternative timer for x86 (default is TSC). HPET counter has constant frequency and does not need calibration. This change also makes TSC timer driver optional on x86. If X86_TSC is disabled, early timer functions are provided by HPET.

Signed-off-by: Ivan Gorinov ivan.gorinov@intel.com

Changelog?

arch/Kconfig | 2 +-

+config HPET_TIMER

•   bool "High Precision Event Timers (HPET) support"
  

•   depends on TIMER && X86
  

Does X86 makes any difference from building point of view?

•   config = readl(regs + HPET_CONFIG_REG);
  

•   config &= ~1;
  

•   writel(config, regs + HPET_CONFIG_REG);
  

1 or BIT(0) is magic. Can be fixed in all places?

•   writel(0, regs + HPET_MAIN_COUNT_L);
  

•   writel(0, regs + HPET_MAIN_COUNT_H);
  

Can we use writeq() here?

•           tl = readl(regs + HPET_MAIN_COUNT_L);
  

•           th = readl(regs + HPET_MAIN_COUNT_H);
  

Ditto.