linux-kernel - Re: [PATCH 1/3] ia64: convert to use clocksource code

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Message-ID: <463219CD.5040203@hp.com>
Date:	Fri, 27 Apr 2007 11:42:05 -0400
From:	Peter Keilty <peter.keilty@...com>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	linux-ia64@...r.kernel.org, John Stultz <johnstul@...ibm.com>,
	Eric Whitney <eric.whitney@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] ia64: convert to use clocksource code

Daniel Walker wrote:

>On Fri, 2007-04-27 at 10:38 -0400, Peter Keilty wrote:
>  
>
>>Daniel Walker wrote:
>>
>>    
>>
>>>On Thu, 2007-04-26 at 16:26 -0400, Peter Keilty wrote:
>>>
>>> 
>>>
>>>      
>>>
>>>>+        .mask           = (1LL << 40) - 1,
>>>>+        .mult           = 0, /*to be caluclated*/
>>>>+        .shift          = 16,
>>>>+        .is_continuous  = 1,
>>>>};
>>>>   
>>>>
>>>>        
>>>>
>>>You should use CLOCKSOURCE_MASK() here ..
>>>
>>> 
>>>
>>>      
>>>
>>It is correct in patch 3, I believe.
>>    
>>
>
>There's another spot that should use CLOCKSOURE_MASK() in the hpet I
>think .
>  
>
Correct that was change in patch 3 also.

>  
>
>>> 
>>>
>>>      
>>>
>>>>diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
>>>>index daa4940..a20b4d6 100644
>>>>--- a/include/linux/clocksource.h
>>>>+++ b/include/linux/clocksource.h
>>>>@@ -61,6 +61,9 @@ struct clocksource {
>>>>	u32 shift;
>>>>	unsigned long flags;
>>>>	cycle_t (*vread)(void);
>>>>+#ifdef CONFIG_IA64
>>>>+	void *fsys_mmio_ptr;	/* used by fsyscall asm code */
>>>>+#endif
>>>>   
>>>>
>>>>        
>>>>
>>>Could you explain in detail why this is needed?
>>> 
>>>
>>>      
>>>
>>This ptr is needed to hold the mmio address to read the cycle value.
>>The fast ia64 path utilizies a special gate page which can allow user
>>code to execute small amount of kernel code, normal calling a function
>>not done and so the address is need. The fast syscall path executes on
>>user stack, between user/kernel state. And if the the fast path has to 
>>fallback
>>to the slow syscall code the vread will be needed and used.
>>    
>>
>
>There is a read(), and a vread() did you modify the slow syscall path to
>use the vread()?
>  
>
I miss type, read().

>Daniel
>
>  
>
-
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