Re: [Xen-devel] [PATCH ARM v7 09/13] mini-os: arm: time

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2014-08-08 at 16:47 +0100, Thomas Leonard wrote:

Sorry for how long I took to get to this, travel and the resulting
backlog conspired against me.

> +    __asm__ __volatile__("isb;mrrc p15, 1, %0, %1, c14":"=r"(c_lo), 
> "=r"(c_hi));

Is the isb really necessary here?

> +    return (((uint64_t) c_hi) << 32) + c_lo;
> +}
> +
> +/* monotonic_clock(): returns # of nanoseconds passed since time_init()
> + *        Note: This function is required to return accurate
> + *        time even in the absence of multiple timer ticks.
> + */
> +uint64_t monotonic_clock(void)
> +{
> +    s_time_t time = ticks_to_ns(read_virtual_count() - cntvct_at_init);
> +    //printk("monotonic_clock: %llu (%llu)\n", time, NSEC_TO_SEC(time));

There's quite a few of these //printk(debug) statements in this patch...

> +    return time;
> +}
> +
> +int gettimeofday(struct timeval *tv, void *tz)
> +{
> +    uint64_t nsec = monotonic_clock();
> +    nsec += shadow_ts.tv_nsec;
> +
> +    tv->tv_sec = shadow_ts.tv_sec;
> +    tv->tv_sec += NSEC_TO_SEC(nsec);
> +    tv->tv_usec = NSEC_TO_USEC(nsec % 1000000000UL);
> +
> +    return 0;
> +}
> +
> +void set_vtimer_compare(uint64_t value) {
> +    uint32_t x, y;
> +
> +    DEBUG("New CompareValue : %llx\n", value);
> +    x = 0xFFFFFFFFULL & value;
> +    y = (value >> 32) & 0xFFFFFFFF;
> +
> +    __asm__ __volatile__("mcrr p15, 3, %0, %1, c14"
> +            ::"r"(x), "r"(y));

I think you can use
        "mcrr p15, 3, %0, %H0, c14" :: "r" (value)
here.


> +
> +    __asm__ __volatile__("mov %0, #0x1\n"
> +            "mcr p15, 0, %0, c14, c3, 1\n" /* Enable timer and unmask the 
> output signal */
> +            "isb":"=r"(x));

x = 1 before this would avoid the mov inside the inline stuff as well as
the strange looking use of an output register for a write.

> +}
> +
> +void unset_vtimer_compare(void) {
> +    uint32_t x;
> +
> +    __asm__ __volatile__("mov %0, #0x2\n"
> +            "mcr p15, 0, %0, c14, c3, 1\n" /* Disable timer and mask the 
> output signal */
> +            "isb":"=r"(x));

and again. You probably just want a write_timer_ctl(uiint.. val) type
function.

> +}
> +
> +void block_domain(s_time_t until)
> +{
> +    uint64_t until_count = ns_to_ticks(until) + cntvct_at_init;
> +    ASSERT(irqs_disabled());
> +    if (read_virtual_count() < until_count)
> +    {
> +        set_vtimer_compare(until_count);
> +        //char buf[] = "sleep\n"; 
> (void)HYPERVISOR_console_io(CONSOLEIO_write, strlen(buf), buf);
> +        __asm__ __volatile__("wfi");
> +        //char wake[] = "wake\n"; 
> (void)HYPERVISOR_console_io(CONSOLEIO_write, strlen(wake), wake);

More left over debug.

> +        unset_vtimer_compare();
> +
> +        /* Give the IRQ handler a chance to handle whatever woke us up. */
> +        local_irq_enable();
> +        local_irq_disable();
> +    }
> +}

Ian.


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