intel efi system too slow

[Sascha Hauer]

Hi Giorgio,

On Wed, Oct 18, 2017 at 12:13:16PM +0200, Giorgio Dal Molin wrote:
> Hi,
> 
> I'm working on an embedded system with an intel CPU (atom).
> 
> I've built a barebox from the current master (v2017.10.0) and it
> runs and can actually boot a kernel.
> 
> Nevertheless I think the bootloader is very slow, for example when
> reading or writing files to the disk (an industrial CFastCard). 
> 
> After the kernel starts the system becomes fast 'es expected'.
> 
> While barebox starts up I noticed the following line on the console:
> 
> ...
> EFI Event timer too slow freq = 50 Hz
> ...
> 
> I found the warning in the source file 'drivers/clocksource/efi.c':
> 
> static int efi_cs_init(struct clocksource *cs)
> {
> 	efi_status_t efiret;
> 	uint64_t freq;
> ...
> 	freq = 1000 * 1000;
> 	if (ticks_freq() < 800 * 1000) {
> 		uint64_t nb_100ns;
> 
> 		freq = ticks_freq_x86();
> 		if (freq == 0) {
> 			BS->close_event(efi_cs_evt);
> 			return -ENODEV;
> 		}
> 		nb_100ns = 10 * 1000 * 1000 / freq;
> 		pr_warn("EFI Event timer too slow freq = %llu Hz\n", freq);
> 		efiret = BS->set_timer(efi_cs_evt, EFI_TIMER_PERIODIC, nb_100ns);
> 		if (EFI_ERROR(efiret)) {
> 			BS->close_event(efi_cs_evt);
> 			return -efi_errno(efiret);
> 		}
> 	}
> ...
> }
> 
> Can this be a possible reason for a too slow system or is it 'OK'
> to see this warning.

Yes, this can be a reason why the system feels slow. a timer frequency
of 50Hz means that the smallest delay barebox can do is 1/50s. This
means that even a udelay(1) will take 20ms.
Try disabling CLOCKSOURCE_EFI (which should be the default in
efi_defconfig). barebox should than use the X86 TSC as clocksource
instead.

Sascha

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