[U-Boot] [PATCH] OMAP3: Fix timer handling to 1ms and CONFIG_SYS_HZ to 1000.

[Dirk Behme]

Dear Jean-Christophe,

Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 11:19 Tue 17 Mar     , Dirk Behme wrote:
>> Fix OMAP3 timer handling to 1ms tick and CONFIG_SYS_HZ to 1000.
>> Clean up macros and comments.
>>
>> Signed-off-by: Dirk Behme <dirk.behme at googlemail.com>
>> Signed-off-by: Manikandan Pillai <mani.pillai at ti.com>
>> ---
>>
>> Changes from Mani's original patch which is replaced by this [1]:
>>
>> * Don't remove overflow handling in get_timer_masked()
>> * Update omap3_zoom1.h, too.
>> * Clean up timer related comments and macros in config files
>> * Don't touch reset_timer_masked()
>> * Switch divider clock divider from 256 to 8 to be able to get 1000Hz
>> * Remove unused udelay_masked()
>> * Minor clean up of get_tbclk()
>>
>> [1] http://lists.denx.de/pipermail/u-boot/2009-March/049012.html
>>
>> This patch is against U-Boot mainline commit
>> 'b3dd629e78870ba2dc9f8032978721c0fa02a856'
>> 'Prepare 2009.03-rc2'
>>
>>  cpu/arm_cortexa8/omap3/interrupts.c |   50 +++++++++++-------------------------
>>  include/configs/omap3_beagle.h      |   11 +++----
>>  include/configs/omap3_evm.h         |   15 +++++-----
>>  include/configs/omap3_overo.h       |   11 +++----
>>  include/configs/omap3_pandora.h     |   11 +++----
>>  include/configs/omap3_zoom1.h       |   11 +++----
>>  6 files changed, 43 insertions(+), 66 deletions(-)
>>
>> Index: u-boot-main/cpu/arm_cortexa8/omap3/interrupts.c
>> ===================================================================
>> --- u-boot-main.orig/cpu/arm_cortexa8/omap3/interrupts.c
>> +++ u-boot-main/cpu/arm_cortexa8/omap3/interrupts.c
>> @@ -169,7 +169,16 @@ static ulong timestamp;
>>  static ulong lastinc;
>>  static gptimer_t *timer_base = (gptimer_t *)CONFIG_SYS_TIMERBASE;
>>  
>> -/* nothing really to do with interrupts, just starts up a counter. */
>> +/*
>> + * Nothing really to do with interrupts, just starts up a counter.
>> + * We run the counter with 13MHz, divided by 8, resulting in timer
>> + * frequency of 1.625MHz. With 32bit counter register, counter
>> + * overflows in ~44min
>> + */
> It will be better to use the 12Mhz source clock and set the divider to 4
> so you will a a timer frequency to 3MHz and a perfect Match clock
> it will overflow ealier but the timer will be exact

Why do you think that existing code doesn't give exact value? With 
this patch we get a nice 1000 Hz tick.

Existing patch is the most non-intrusive (i.e. touch only what's 
necessary), easy and small fix for broken OMAP3 timer code. And it 
gives fine 1000 Hz. Yes, everything can be done more perfect. But 
often this isn't necessary. So please apply this version.

Dirk

Btw.: Could be agree on the "without too long delays" part of

http://lists.denx.de/pipermail/u-boot/2009-March/049885.html

?