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

From: Ian Campbell
Subject: Re: [PATCH] * grub-core/kern/uboot/init.c (uboot_timer_ms) correct units
Date: Sun, 22 Dec 2013 01:29:35 +0000

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 <address@hidden>
> > > 
> > > 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
> > >
> > > 
> > 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 <address@hidden>
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 <address@hidden>

and from README:

- CPU timer options:

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


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