[PATCH] [POWERPC] 8xx: timebase frequency should not depend on bus-frequency
Scott Wood
scottwood at freescale.com
Fri Feb 22 07:06:58 EST 2008
Anton Vorontsov wrote:
> On Thu, Feb 21, 2008 at 01:48:23PM -0600, Scott Wood wrote:
>> Anton Vorontsov wrote:
>>> diff --git a/arch/powerpc/platforms/8xx/m8xx_setup.c
>>> b/arch/powerpc/platforms/8xx/m8xx_setup.c
>>> index 184f998..0d9f75c 100644
>>> --- a/arch/powerpc/platforms/8xx/m8xx_setup.c
>>> +++ b/arch/powerpc/platforms/8xx/m8xx_setup.c
>>> @@ -111,17 +111,12 @@ void __init mpc8xx_calibrate_decr(void)
>>>
>>> /* Processor frequency is MHz.
>>> */
>>> - ppc_tb_freq = 50000000;
>>> - if (!get_freq("bus-frequency", &ppc_tb_freq)) {
>>> - printk(KERN_ERR "WARNING: Estimating decrementer frequency "
>>> - "(not found)\n");
>>> - }
>>> - ppc_tb_freq /= 16;
>>> ppc_proc_freq = 50000000;
>>> if (!get_freq("clock-frequency", &ppc_proc_freq))
>>> printk(KERN_ERR "WARNING: Estimating processor frequency "
>>> "(not found)\n");
>>>
>>> + ppc_tb_freq = ppc_proc_freq / 16;
>> Shouldn't we just use the timebase-frequency property?
>
> Nope. Most u-boots currently do not setup timebase-frequency, and if
> they are setting it up, they're doing it wrong, in sense that Linux
> overwrites timebase setup (yeah, in this regard MPC8xx is special).
Current u-boots don't support device trees at all on 8xx. The most
recent 8xx FDT patch I saw called get_tbclk() to fill in
timebase-frequency; does get_tbclk() not work?
Obviously, when booting with a cuImage we can't use u-boot's value,
since it's not in the bd_t. In that case, we should fix the wrapper's
calculation of the timebase frequency.
-Scott
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