linux-kernel - Re: [PATCH] ACPI: implement acpi_os_get

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Date:	Mon, 20 May 2013 13:07:35 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	linux-acpi@...r.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Len Brown <lenb@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: implement acpi_os_get_timer() according the spec

On Monday, May 20, 2013 01:25:30 PM Mika Westerberg wrote:
> On Mon, May 13, 2013 at 02:44:32PM +0300, Mika Westerberg wrote:
> > On Mon, May 13, 2013 at 01:38:46PM +0200, Rafael J. Wysocki wrote:
> > > On Monday, May 13, 2013 01:27:51 PM Mika Westerberg wrote:
> > > > ACPI Timer() opcode should return monotonically increasing clock with 100ns
> > > > granularity. Implement this with the help of ktime_get().
> > > > 
> > > > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> > > 
> > > That looks reasobable.  Have you tested it?
> > 
> > Very lightly. Basically I added some debug printks() between two
> > successsive calls of Timer() and it seemed like it returned correct time.
> > 
> > It is certainly better than returning t+1 every time Timer() is called :)
> 
> I did somewhat better test for this. I added following ASL code:
> 
> 	...
> 	Store(Timer, Local1)
> 	Sleep(10)
> 	Divide(Subtract(Timer, Local1), 10000,, Local1)
> 	Sleep(Local1)
> 
> 	Store(Timer, Local1)
> 	Sleep(200)
> 	Divide(Subtract(Timer, Local1), 10000,, Local1)
> 	Sleep(Local1)
> 
> 	Store(Timer, Local1)
> 	Sleep(1300)
> 	Divide(Subtract(Timer, Local1), 10000,, Local1)
> 	Sleep(Local1)
> 
> The second sleep should be pretty close to the first one.
> 
> Without this patch I get:
> 
> [   11.488100] ACPI: acpi_os_get_timer() TBD
> [   11.492150] ACPI: Sleep(10)
> [   11.502993] ACPI: Sleep(0)
> [   11.506315] ACPI: Sleep(200)
> [   11.706237] ACPI: Sleep(0)
> [   11.709550] ACPI: Sleep(1300)
> [   13.008929] ACPI: Sleep(0)
> 
> With the patch applied I get:
> 
> [   11.486786] ACPI: Sleep(10)
> [   11.499029] ACPI: Sleep(12)
> [   11.512350] ACPI: Sleep(200)
> [   11.712282] ACPI: Sleep(200)
> [   11.912170] ACPI: Sleep(1300)
> [   13.211577] ACPI: Sleep(1300)
> 
> The above looks much more correct to me.

That demostrates the problem nicely.  Can you please add the above info to the
patch changelog?

Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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