linux-kernel - Re: [PATCH 1/3] fix debug message of CPU clock speed

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Date:	Wed, 28 Jan 2009 11:33:17 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	linux-kernel@...r.kernel.org, mingo@...hat.com
Subject: Re: [PATCH 1/3] fix debug message of CPU clock speed

Hi, Ingo

Thank you for your comments.
I apply your comments to the patch ASAP.

Regard,
Yasuaki Ishimatsu

Ingo Molnar wrote:
> * Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com> wrote:
> 
>> LOCAL APIC is corrected by PM-Timer, when SMI occurred while LOCAL APIC 
>> is calibrated. In this case, LOCAL APIC debug message(Boot with 
>> apic=debug) is displayed correctly, however, CPU clock speed debug 
>> message is displayed wrongly .
> 
> your fix looks good, but there are a few minor style details that need to 
> be addressed:
> 
>> When SMI occured on my machine, which has 1.6GHz CPU, CPU clock speed is 
>> displayed 3622.0205 MHz as follow.
>>
>> 	CPU0: Intel(R) Xeon(R) CPU            5110  @ 1.60GHz stepping 06
>> 	Using local APIC timer interrupts.
>> 	calibrating APIC timer ...
>> 	... lapic delta = 3773130
>> 	... PM timer delta = 812434
>> 	APIC calibration not consistent with PM Timer: 226ms instead of 100ms
>> 	APIC delta adjusted to PM-Timer: 1662420 (3773130)
>> 	..... delta 1662420
>> 	..... mult: 71411249
>> 	..... calibration result: 265987
>> 	..... CPU clock speed is 3622.0205 MHz.  =====>  here
>> 	..... host bus clock speed is 265.0987 MHz.
>>
>> This patch fixes to displaying CPU clock speed correctly as follow.
>>
>> 	CPU0: Intel(R) Xeon(R) CPU            5110  @ 1.60GHz stepping 06
>> 	Using local APIC timer interrupts.
>> 	calibrating APIC timer ...
>> 	... lapic delta = 3773131
>> 	... PM timer delta = 812434
>> 	APIC calibration not consistent with PM Timer: 226ms instead of 100ms
>> 	APIC delta adjusted to PM-Timer: 1662420 (3773131)
>> 	TSC delta adjusted to PM-Timer: 159592409 (362220564)
>> 	..... delta 1662420
>> 	..... mult: 71411249
>> 	..... calibration result: 265987
>> 	..... CPU clock speed is 1595.0924 MHz.
>> 	..... host bus clock speed is 265.0987 MHz.
>>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>
>> ---
>>  arch/x86/kernel/apic.c |   23 +++++++++++++++++------
>>  1 file changed, 17 insertions(+), 6 deletions(-)
>>
>> Index: linux-2.6.29-rc2/arch/x86/kernel/apic.c
>> ===================================================================
>> --- linux-2.6.29-rc2.orig/arch/x86/kernel/apic.c	2009-01-27 11:04:40.000000000 +0900
>> +++ linux-2.6.29-rc2/arch/x86/kernel/apic.c	2009-01-27 12:29:03.000000000 +0900
>> @@ -535,7 +535,8 @@ static void __init lapic_cal_handler(str
>>  	}
>>  }
>>
>> -static int __init calibrate_by_pmtimer(long deltapm, long *delta)
>> +static int __init calibrate_by_pmtimer(long deltapm, long *delta,
>> +						long *deltatsc)
> 
> The cleaner prototype line-width break is:
> 
>   + static int __init
>   + calibrate_by_pmtimer(long deltapm, long *delta, long *deltatsc)
> 
> 
> this function:
> 
>> @@ -569,6 +570,15 @@ static int __init calibrate_by_pmtimer(l
>>  		pr_info("APIC delta adjusted to PM-Timer: "
>>  			"%lu (%ld)\n", (unsigned long)res, *delta);
>>  		*delta = (long)res;
>> +
>> +		if (cpu_has_tsc) {
>> +			res = (((u64)(*deltatsc)) * pm_100ms);
>> +			do_div(res, deltapm);
>> +			apic_printk(APIC_VERBOSE, "TSC delta adjusted to "
>> +					"PM-Timer: %lu (%ld)\n",
>> +					(unsigned long)res, *deltatsc);
>> +			*deltatsc = (long)res;
>> +		}
> 
> has too deep nesting in the form of:
> 
> 	if (A) {
> 		...
> 	} else {
> 		...
> 		if (B) {
> 			...
> 		}
> 	}
> 
> 	return 0;
> 
> 
> Could you please restructure it to a cleaner control flow, in the form of:
> 
> 	if (A) {
> 		...
> 		return 0;
> 	}
> 	...
> 	if (B) {
> 		...
>   	}
> 
> 	return 0;
> 
> ?
> 
> Thanks,
> 
> 	Ingo
> 

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