Re: [U-Boot] [PATCH v4] timer: Add High Precision Event Timers (HPET) support

On Fri, 2018-04-06 at 10:38 -0700, Ivan Gorinov wrote:

Add HPET driver 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. New HPET driver can also be selected as the early timer on x86.

+/* Reset and start the main counter. */ +static void start_main_counter(void *regs) +{

• volatile u64 *main_counter = regs + HPET_MAIN_COUNT;
• u32 config;
• config = readl(regs + HPET_CONFIG_REG);
• config &= ~ENABLE_CNF;
• writel(config, regs + HPET_CONFIG_REG);

• *main_counter = 0;

It needs to be done as writeq() / readq().

Please, define them first in arch/x86/include/asm/io.h (as an example you can use arch/arm/include/asm/io.h).

• config |= ENABLE_CNF;
• writel(config, regs + HPET_CONFIG_REG);

+}

+/* Read the main counter, repeat if 32-bit rollover happens. */ +static u64 read_main_counter(void *regs) +{

• volatile u64 *main_counter = regs + HPET_MAIN_COUNT;
• u64 t, t0;
• t = *main_counter;
• do {

• t0 = t;
  

• t = *main_counter;
  

Ditto.

• } while ((t >> 32) != (t0 >> 32));
• return t;

+}