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

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: [PATCH] * grub-core/kern/uboot/init.c (uboot_timer_ms) correct units
Date: Sun, 22 Dec 2013 02:52:30 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20131103 Icedove/17.0.10

On 22.12.2013 02:29, Ian Campbell wrote:
> 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:
Ok, I've kept current code as generic and added own timer implementation
for raspberry pie
> 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:
>                 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.

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