Fw: Re: [PATCH 1/5] RT kernel: force detect HPET from PCI space

Fw: Re: [PATCH 1/5] RT kernel: force detect HPET from PCI space

[Andrew Morton]

I assume this is an acpi table bug.

Is there any way in which we can get a workaround in place to fix this for real?


Begin forwarded message:

Date: Sat, 31 Mar 2007 18:00:34 +0300 (EEST)
From: Mikko Tiihonen <mikko.tiihonen@iki.fi>
To: Nicolas Mailhot <nicolas.mailhot@laposte.net>
Cc: Krzysztof Halasa <khc@pm.waw.pl>, linux-kernel@vger.kernel.org, ranma@tdiedrich.de, om.turyx@gmail.com
Subject: Re: [PATCH 1/5] RT kernel: force detect HPET from PCI space




On Sat, 31 Mar 2007, Nicolas Mailhot wrote:

> [adding some people in CC that expressed interest in the problem before]
>
> I'm crazy enough to test a patch if someone cooks it, but I'm way out of
> my depth there :)

After struggling with totally broken kernels for the whole morning I got the 
HPET to work with my NForce4 with the following hard coded ACPI quirk. My 
machine has been now stable for few hours and I tested that the HPET really 
seems to be working by switching the clock source using

echo hpet|tsc|acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource

Results of a simple benchmark show that the time to execute gettimeofday 
really varies based on the clock source: (performance normalised to tsc)
tsc:      1x
hpet:     4x
acpi_pm: 12x

At least on my motherboard it seems to be enough to just grab the HPET address 
from the lspci output and not bother with any of the other changing bits.

--- linux-2.6.21-rc5-git5/arch/i386/kernel/acpi/boot.c	2007-03-31 17:49:24.000000000 +0300
+++ linux-2.6.21-rc5-git5.hpet/arch/i386/kernel/acpi/boot.c	2007-03-31 17:02:27.000000000 +0300
@@ -1189,6 +1189,8 @@ int __init acpi_boot_table_init(void)

  int __init acpi_boot_init(void)
  {
+        struct acpi_table_hpet hpet_tbl;
+
  	/*
  	 * If acpi_disabled, bail out
  	 * One exception: acpi=ht continues far enough to enumerate LAPICs
@@ -1208,7 +1210,12 @@ int __init acpi_boot_init(void)
  	 */
  	acpi_process_madt();

-	acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
+	hpet_tbl.address.address = 0xfefff000L;
+	hpet_tbl.address.space_id = ACPI_SPACE_MEM;
+	hpet_tbl.sequence = 0;
+	hpet_tbl.id = 0xbabe;
+        acpi_parse_hpet((struct acpi_table_header *) &hpet_tbl);
+	//	acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);

  	return 0;
  }

-Mikko
-
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Re: Fw: Re: [PATCH 1/5] RT kernel: force detect HPET from PCI space

[Mikko Tiihonen]

On Sat, 31 Mar 2007, Andrew Morton wrote:

>
> I assume this is an acpi table bug.

Yes. BIOS seems to initialise the HPET correctly (or then the HW needs no 
setup) but just forgets to add the entry to acpi table.

So far I have received report that my hack works on
CK804 ISA Bridge 10de:0050
MCP55 LPC Bridge (pci id most likely one of 10de:0360 - 10de:0367)

It seems that for most (all?) nvidia chipsets the hpet address can be read
with pci_read_config_dword(dev, 0x44, &addr) from the correct device.

> Is there any way in which we can get a workaround in place to fix this for real?

I have been thinking of a way for early quirks that could add fake acpi table 
entries. The acpi_table_parse function could then be modified to 
scan also the fake entries, which would just already contain the acpi structs.

Another way is to do as Venkatesh did for intel chipsets. Add a early quirk 
that exports force_hpet_address and teach hpet driver to try it too. I do not 
think this will not work properly however, unless the reserving of the hpet 
iomem resource is moved from i386/kernel/acpi/boot.c to the hpet driver.

> Begin forwarded message:
>
> Date: Sat, 31 Mar 2007 18:00:34 +0300 (EEST)
> From: Mikko Tiihonen <mikko.tiihonen@iki.fi>
> To: Nicolas Mailhot <nicolas.mailhot@laposte.net>
> Cc: Krzysztof Halasa <khc@pm.waw.pl>, linux-kernel@vger.kernel.org, ranma@tdiedrich.de, om.turyx@gmail.com
> Subject: Re: [PATCH 1/5] RT kernel: force detect HPET from PCI space
>
>
>
>
> On Sat, 31 Mar 2007, Nicolas Mailhot wrote:
>
>> [adding some people in CC that expressed interest in the problem before]
>>
>> I'm crazy enough to test a patch if someone cooks it, but I'm way out of
>> my depth there :)
>
> After struggling with totally broken kernels for the whole morning I got the
> HPET to work with my NForce4 with the following hard coded ACPI quirk. My
> machine has been now stable for few hours and I tested that the HPET really
> seems to be working by switching the clock source using
>
> echo hpet|tsc|acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
>
> Results of a simple benchmark show that the time to execute gettimeofday
> really varies based on the clock source: (performance normalised to tsc)
> tsc:      1x
> hpet:     4x
> acpi_pm: 12x
>
> At least on my motherboard it seems to be enough to just grab the HPET address
> from the lspci output and not bother with any of the other changing bits.
>
> --- linux-2.6.21-rc5-git5/arch/i386/kernel/acpi/boot.c	2007-03-31 17:49:24.000000000 +0300
> +++ linux-2.6.21-rc5-git5.hpet/arch/i386/kernel/acpi/boot.c	2007-03-31 17:02:27.000000000 +0300
> @@ -1189,6 +1189,8 @@ int __init acpi_boot_table_init(void)
>
>  int __init acpi_boot_init(void)
>  {
> +        struct acpi_table_hpet hpet_tbl;
> +
>  	/*
>  	 * If acpi_disabled, bail out
>  	 * One exception: acpi=ht continues far enough to enumerate LAPICs
> @@ -1208,7 +1210,12 @@ int __init acpi_boot_init(void)
>  	 */
>  	acpi_process_madt();
>
> -	acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
> +	hpet_tbl.address.address = 0xfefff000L;
> +	hpet_tbl.address.space_id = ACPI_SPACE_MEM;
> +	hpet_tbl.sequence = 0;
> +	hpet_tbl.id = 0xbabe;
> +        acpi_parse_hpet((struct acpi_table_header *) &hpet_tbl);
> +	//	acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
>
>  	return 0;
>  }
>
> -Mikko
> -
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>