https://bugzilla.kernel.org/show_bug.cgi?id=41042
--- Comment #2 from Jose Alonso <joalon...@gmail.com> 2011-08-14 16:35:46 ---
To debug this, I boot the kernel in single mode, using one cpu and outputing
the kernel messages to console. I set the acpi parameters debug_level and
debug_layer and put some printk.
The machine freezes showing the last message: "start outb(0x79, 0xb2)"
--- a/drivers/acpi/osl.c
+++ b/drivers/acpi/osl.c
@@ -638,7 +638,12 @@ EXPORT_SYMBOL(acpi_os_read_port);
acpi_status acpi_os_write_port(acpi_io_address port, u32 value, u32 width)
{
if (width <= 8) {
- outb(value, port);
+ if (port == (acpi_io_address)0xb2 && value == 0x79) {
+ printk("start outb(0x79, 0xb2)\n");
+ outb(value, port);
+ printk("end outb(0x79, 0xb2)\n");
+ } else
+ outb(value, port);
} else if (width <= 16) {
outw(value, port);
} else if (width <= 32) {
-----------------
This corresponds in file DSDT.dsl to:
...
OperationRegion (GNVS, SystemMemory, 0xBB622E18, 0x0172)
Field (GNVS, AnyAcc, Lock, Preserve)
{
...
BRTL, 8, <---------
...
OperationRegion (EXBU, SystemMemory, 0xBB62F018, 0x1011)
Field (EXBU, AnyAcc, Lock, Preserve)
{
...
SMIB, 8, <----------
...
Scope (_SB.PCI0.GFX0)
...
Device (DD02)
...
Method (_BCM, 1, NotSerialized) <-------(1)
{
SX10 ()
SX30 (0x19)
SX30 (One)
SX30 (Arg0)
Store (Arg0, BRTL)
SX11 () <---------(2)
SX12 ()
}
...
Scope (_SB)
{
OperationRegion (SMIR, SystemIO, 0xB2, 0x02)
Field (SMIR, ByteAcc, NoLock, Preserve)
{
SMII, 8, <-------------
...
Method (SX11, 0, NotSerialized)
{
If (LEqual (NSMI, Zero))
{
SXX4 ()
Store (SXX6 (0x79, Zero), SXX3) <-------(3)
...
Method (SXX6, 2, NotSerialized)
{
Store (Arg1, SMIB)
Store (Arg0, \_SB.SMII) <--------(4)(here)
Return (SMIB)
}
----------------------------
Sequence to change brightness:
brightness -> BRTL
0 -> SMIB
outb(0x7b, 0xb2) (value,port)
SMIB -> return value not used
0x19 -> SMIB
outb(0x7c, 0xb2)
SMIB -> return value not used
1 -> SMIB
outb(0x7c, 0xb2)
SMIB -> return value not used
brightness -> SMIB
outb(0x7c, 0xb2)
SMIB -> return value not used
0 -> SMIB
outb(0x79, 0xb2) <---------(here)
SMIB -> return value = 0 (no return arguments)
-------------------------------
Seems that the CPU cannot use the PCI/IO bus ?!?
I suspect it is a timing problem or
some interference with bus usage.
I don't know if its a Dell hardware specific or
intel chipset.
Any clue?
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