Re: [XenPPC] NAP state

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

On Oct 10, 2006, at 1:12 PM, Amos Waterland wrote:

> Just as a sanity check, is the intention is to put the processor in  
> the
> NAP state when .sleep() is invoked?  If so, is the following behavior
> expected?
Yes!
Sleep turns the EE bit on and you have enabled HDEC so they are both  
firing waking you from sleep at different times
Also if you take 0x7fffffff/timebase_freq you'll find it is about 9  
seconds :)
To demonstrate let modify the patch a little:
diff -r 294577be7c02 xen/arch/powerpc/setup.c
--- a/xen/arch/powerpc/setup.c  Tue Oct 10 12:02:56 2006 -0400
+++ b/xen/arch/powerpc/setup.c  Tue Oct 10 13:46:30 2006 -0400
@@ -403,6 +403,16 @@ static void __init __start_xen(multiboot
     console_endboot();
+    printk("tbf: %d\n", timebase_freq);
+    while (1) {
+        long before, after;
+        printk(">>dec %d hdec %d\n", mfdec(), mfhdec());
+        before = mftb(); sleep(); after = mftb();
+        printk("<<dec %d hdec %d\n", mfdec(), mfhdec());
+        printk("hid0 = %lx: slept for %ld timebase ticks (%ld  
seconds)\n",
+               mfhid0(), after - before, (after - before) /  
timebase_freq);
+    }
+
     /* Hide UART from DOM0 if we're using it */
     serial_endboot();


output is (comments with >>):

(XEN) tbf: 175000000
>> 0x7fffffff/175000000 = 9

(XEN) >>dec 13921793 hdec 2112442338
>>>         ^^^^^^^^
(XEN) <<dec 2147418095 hdec 2098520480
(XEN) hid0 = 51010180000000: slept for 13369891 timebase ticks (0  
seconds)
>>> matches                            ^^^^^^^^
(XEN) >>dec 2145746886 hdec 2096849271
>>>>                        ^^^^^^^^^^
(XEN) <<dec 48897109 hdec 2147483491
(XEN) hid0 = 51010180000000: slept for 2096268461 timebase ticks (11  
seconds)
>>>> matches                           ^^^^^^^^^^


I am however surprised that HDEC will wake from any kind of sleep,  
Cell and P5+ processors do not do this.
-JX


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