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SubjectRe: 2.6.35-rc3 regression: IBM Maia system is unbootable [ACPI related?]
From: Len Brown <len.brown@intel.com>
Subject: [PATCH] ACPI: handle systems which asynchoronously enable ACPI mode

Folklore suggested that such systems existed
in the pre-history of ACPI.

However, we removed the SCI_EN polling loop from
acpi_hw_set_mode() in b430acbd7c4b919886fa7fd92eeb7a695f1940d3
because it delayed resume by 3 seconds on boxes
that refused to set SCI_EN.

Matthew removed the call to acpi_enable() from
the suspend resume path.

James found a modern system that still needs to be polled
upon boot.

So here we restore the workaround, except that we
put it in acpi_enable() rather than the low level
acpi_hw_set_mode().

https://bugzilla.kernel.org/show_bug.cgi?id=16271

Signed-off-by: Len Brown <len.brown@intel.com>
---

James, What does the IBM system see with this patch?

thanks,
-Len

drivers/acpi/acpica/evxfevnt.c | 19 +++++++++++--------
1 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/acpica/evxfevnt.c b/drivers/acpi/acpica/evxfevnt.c
index d97b8dc..18b3f14 100644
--- a/drivers/acpi/acpica/evxfevnt.c
+++ b/drivers/acpi/acpica/evxfevnt.c
@@ -70,6 +70,7 @@ acpi_ev_get_gpe_device(struct acpi_gpe_xrupt_info *gpe_xrupt_info,
acpi_status acpi_enable(void)
{
acpi_status status;
+ int retry;

ACPI_FUNCTION_TRACE(acpi_enable);

@@ -98,16 +99,18 @@ acpi_status acpi_enable(void)

/* Sanity check that transition succeeded */

- if (acpi_hw_get_mode() != ACPI_SYS_MODE_ACPI) {
- ACPI_ERROR((AE_INFO,
- "Hardware did not enter ACPI mode"));
- return_ACPI_STATUS(AE_NO_HARDWARE_RESPONSE);
+ for (retry = 0; retry < 30000; ++retry) {
+ if (acpi_hw_get_mode() == ACPI_SYS_MODE_ACPI) {
+ if (retry != 0)
+ ACPI_WARNING((AE_INFO,
+ "Platform took > %d00 usec to enter ACPI mode", retry));
+ return_ACPI_STATUS(AE_OK);
+ }
+ acpi_os_stall(100); /* 100 usec */
}

- ACPI_DEBUG_PRINT((ACPI_DB_INIT,
- "Transition to ACPI mode successful\n"));
-
- return_ACPI_STATUS(AE_OK);
+ ACPI_ERROR((AE_INFO, "Hardware did not enter ACPI mode"));
+ return_ACPI_STATUS(AE_NO_HARDWARE_RESPONSE);
}

ACPI_EXPORT_SYMBOL(acpi_enable)
--
1.7.2.rc0


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