[Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[Jason Wessel]

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This patch implements a simple 24mhz clock for the versatile board such 
that functions in the linux kernel can make use of these stamps.  An 
example user of this is the printk time stamps when using the "time" 
parameter on the kernel boot line.

signed-off-by: jason.wessel@windriver.com

Cheers,
Jason.

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Index: qemu/hw/arm_sysctl.c
===================================================================
--- qemu.orig/hw/arm_sysctl.c
+++ qemu/hw/arm_sysctl.c
@@ -71,8 +71,10 @@ static uint32_t arm_sysctl_read(void *op
     case 0x58: /* BOOTCS */
         return 0;
     case 0x5c: /* 24MHz */
-        /* ??? not implemented.  */
-        return 0;
+    {   
+        uint64_t now = qemu_get_clock(vm_clock);
+        return (uint32_t)(now*.024);
+    }
     case 0x60: /* MISC */
         return 0;
     case 0x84: /* PROCID0 */

Re: [Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[Paul Brook]

> +        uint64_t now = qemu_get_clock(vm_clock);
> +        return (uint32_t)(now*.024);

We should be able to do this without resorting to floating point arithmetic.

Paul

Re: [Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[Jonathan Kalbfeld]

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If you're ok you can shift it left 4 bits, then add half that result then
shift right 10 bits.

Of course, you'll only get 23.4Mhz that way :-)

jonathan

On 3/30/07, Paul Brook <paul@codesourcery.com> wrote:
>
> > + uint64_t now = qemu_get_clock(vm_clock);
> > + return (uint32_t)(now*.024);
>
> We should be able to do this without resorting to floating point
> arithmetic.
>
> Paul
>
>
>


-- 
--
Jonathan Kalbfeld
+1 323 620 6682

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RE: [Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[Wessel, Jason]

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uint64_t now = qemu_get_clock(vm_clock);
return (uint32_t)((now*3)/125);

The optimizer should fix this up with no floating point ops.
 
Jason.



________________________________

	From: qemu-devel-bounces+jason.wessel=windriver.com@nongnu.org
[mailto:qemu-devel-bounces+jason.wessel=windriver.com@nongnu.org] On
Behalf Of Jonathan Kalbfeld
	Sent: Friday, March 30, 2007 12:50 PM
	To: qemu-devel@nongnu.org
	Subject: Re: [Qemu-devel] [PATCH] add a simple 24mhz clock for
the versatile
	
	
	If you're ok you can shift it left 4 bits, then add half that
result then shift right 10 bits.
	
	Of course, you'll only get 23.4Mhz that way :-)
	
	jonathan
	
	
	On 3/30/07, Paul Brook <paul@codesourcery.com> wrote: 

		> + uint64_t now = qemu_get_clock(vm_clock);
		> + return (uint32_t)(now*.024);
		
		We should be able to do this without resorting to
floating point arithmetic.
		
		Paul
		
		
		




	-- 
	--
	Jonathan Kalbfeld
	+1 323 620 6682 


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Re: [Qemu-devel] [PATCH] add a simple 24mhz clock for the versatile

[andrzej zaborowski]

On 31/03/07, Wessel, Jason <jason.wessel@windriver.com> wrote:
>
>
> uint64_t now = qemu_get_clock(vm_clock);
> return (uint32_t)((now*3)/125);
>
> The optimizer should fix this up with no floating point ops.

Adding to the bikeshed discussion (www.bikeshed.com) this is still not
correct as vm_clock is to be used with ticks_per_sec.

return muldiv64(qemu_get_clock(vm_clock), 24000000, ticks_per_sec);

Regards,
Andrzej