linux-kernel - Re: [PATCH 9/10] Vmi timer update.patch

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Message-ID: <461C16E0.6010702@vmware.com>
Date:	Tue, 10 Apr 2007 15:59:44 -0700
From:	Zachary Amsden <zach@...are.com>
To:	Chris Wright <chrisw@...s-sol.org>
CC:	Andrew Morton <akpm@...l.org>, Andi Kleen <ak@....de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Virtualization Mailing List <virtualization@...ts.osdl.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 9/10] Vmi timer update.patch

Chris Wright wrote:
> * Zachary Amsden (zach@...are.com) wrote:
>   
>> Yes, but unfortunately that is a nop:
>>
>>         /*
>>          * Avoid unnecessary state transitions, as it confuses
>>          * Geode / Cyrix based boxen.
>>          */
>>         case CLOCK_EVT_MODE_SHUTDOWN:
>>                 if (evt->mode == CLOCK_EVT_MODE_UNUSED)
>>                         break;
>>         case CLOCK_EVT_MODE_UNUSED:
>>                 if (evt->mode == CLOCK_EVT_MODE_SHUTDOWN)
>>                         break;
>>     
>
> This one should be fallthrough case during exchange (mode == PERIODIC)
>   

Yes, seems PERIODIC->SHUTDOWN should do the right thing.


>>         case CLOCK_EVT_MODE_ONESHOT:
>>                 /* One shot setup */
>>                 outb_p(0x38, PIT_MODE);
>>
>> So switching from PIT to VMI does not disable PIT timer interrupts.  
>> Thus I have to keep this part of the patch.
>>     

Since I misread the code, I can drop this now.


>
> Oh, I was looking at this (x86_64 work I have here):
>
> 	case CLOCK_EVT_MODE_SHUTDOWN:
> 	case CLOCK_EVT_MODE_UNUSED:
> 		outb_p(0x30, PIT_MODE);
> 		outb_p(0, PIT_CH0);	/* LSB */
> 		outb_p(0, PIT_CH0);	/* MSB */
> 		break;
>
> That's mode 0, not mode 5, but I think the end result is the same.
>   

Yes, mode 0, 4, 5 all should behave similarly.

Zach
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