Re: [PATCH] * grub-core/kern/uboot/init.c (uboot_timer_ms) correct units

[Ian Campbell <ijc@hellion.org.uk>]

On Sun, 2013-12-22 at 01:21 +0000, Ian Campbell wrote:
> On Sat, 2013-12-21 at 23:23 +0100, Vladimir 'φ-coder/phcoder' Serbinenko
> wrote:
> > On 15.12.2013 16:23, Ian Campbell wrote:
> > > From: Ian Campbell <ian.campbell@citrix.com>
> > > 
> > > u-boot's API_GET_TIMER returns the current time in ms by directly exposing the
> > > internal get_timer which is in ms, which isn't all that clearly documented but
> > > is obvious from the use within u-boot and is mentioned in
> > > http://www.denx.de/wiki/U-Boot/TaskTimerAPI.
> > > 
> > During tests on my raspberry pi, I actually experienced the exact
> > opposite. On PI timer API is in microseconds.
> > Are you sure you made no mistake?
> 
> I'm quite sure that on the Midway platform get_timer was returning ms
> and the 5s grub countdown took 5s after my fix and some interminably
> long time before it.
> 
> Sadly actual documentation of the u-boot API is a bit thin on the
> ground, but get_timer==ms is also corroborated by some ad-hoc googling I
> did (e.g. resulting in the above link) as well as inspection of some
> random u-boot ports. Some ports have an explicit get_timer_us function,
> which adds credence to the idea that get_timer is in ms instead.

See also this patch to u-boot upstream:

commit 5eaa215607c8668bfa6a7183407eba8fec63d648
Author: Stephen Warren <swarren@wwwdotorg.org>
Date:   Wed Mar 27 18:43:23 2013 +0000

    ARM: bcm2835: fix get_timer() to return ms
    
    Apparently, CONFIG_SYS_HZ must be 1000. Change this, and fix the timer
    driver to conform to this.
    
    Have the timer implementation export a custom API get_timer_us() for use
    by the BCM2835 MMC API, which needs us resolution for a HW workaround.
    
    Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>

and from README:

- CPU timer options:
                CONFIG_SYS_HZ

                The frequency of the timer returned by get_timer().
                get_timer() must operate in milliseconds and this CONFIG
                option must be set to 1000.

Ian.