From mboxrd@z Thu Jan  1 00:00:00 1970
From: Simon Schwarz <schwarz@corscience.de>
Date: Thu, 21 Apr 2011 14:13:38 +0200
Subject: [U-Boot] The forbidden value in omap3-common timer.c code
Message-ID: <4DB01F72.9070504@corscience.de>
List-Id: <u-boot.lists.denx.de>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: u-boot@lists.denx.de

Hi there,

I just started to work with the u-boot sources for my bachelor thesis. 
There was a part in the source which irritated me a bit.

I talk about ./arch/arm/cpu/armv7/omap-common/timer.c

It's about that part of code:
#define TIMER_LOAD_VAL  0xffffffff

int timer_init(void)
{
         /* start the counter ticking up, reload value on overflow */
         writel(TIMER_LOAD_VAL, &timer_base->tldr);
         /* enable timer */
         writel((CONFIG_SYS_PTV << 2) | TCLR_PRE | TCLR_AR | TCLR_ST,
&timer_base->tclr);

         reset_timer_masked();   /* init the timestamp and lastinc value */

         return 0;
}


The tldr ist loaded with 0xFFFFFFFF.

The OMAP35x Technical Reference Manual (Rev. P) says on page 2583:
Do not put the overflow value (0xFFFFFFFF) in the GPTi.TLDR register
because it can lead to undesired results.

Is there a reason why the value is used nevertheless? At this time I 
don't know where the timer is used, maybe the "undesired results" 
haven't been noticed yet?

Thanks!
Simon

-- 
-------------------------------------------------
Simon Schwarz

Corscience GmbH&  Co. KG
Henkestra?e 91
D-91052 Erlangen

e-mail: schwarz at corscience.de
Internet: www.corscience.de
-------------------------------------------------
Corscience GmbH&  Co.KG
Sitz der Gesellschaft/Place of business: Erlangen
Amtsgericht/Local court: F?rth
Handelsregisternummer/Commercial Register No.: HRA 7510
Gesch?ftsf?hrer/Managing director: Prof. Dr. Armin Bolz,
Dr. Karl-Andreas Feldhahn, Dipl.-Volksw. Marc Griefahn

CONFIDENTIALITY:
This e-mail and any attachments are confidential and may also be
privileged. If received in error, please do not disclose the contents
to anyone, but notify us immediately by return e-mail and delete this
e-mail and any attachments from your system. Thank you.