Add a new boot option related to HPET. Current mode of HPET functioning:
(1) If HPET is listed in BIOS:
default: HPET gets detected at boot time and gets enabled in
"legacy replacement" mode.
"hpet=standard" boot option: HPET does not get used during early boot and
PIT will be used in early boot. HPET gets enabled in "standard" mode during
late boot stages.
"hpet=disable" boot option: HPET is disabled and not used.
(2) If HPET is not listed in BIOS and force detected with PCI quirks:
default: HPET does not get used during early boot and
PIT will be used in early boot. HPET gets enabled in "standard" mode during
late boot stages.
"hpet=disable" boot option: HPET is disabled and not used.
We can change the default behavior of (1) to match (2) after this patch gets
some testing.
Signed-off-by: Venkatesh Pallipadi <[email protected]>
Index: linux-2.6.21/include/asm-i386/hpet.h
===================================================================
--- linux-2.6.21.orig/include/asm-i386/hpet.h 2007-04-27 15:27:12.000000000 -0700
+++ linux-2.6.21/include/asm-i386/hpet.h 2007-04-27 15:30:22.000000000 -0700
@@ -112,7 +112,7 @@
extern int is_hpet_capable(void);
extern int hpet_readl(unsigned long a);
#else
-extern int hpet_enable(void);
+extern int hpet_enable(int early_call);
#endif
#ifdef CONFIG_HPET_EMULATE_RTC
@@ -127,7 +127,7 @@
#else
-static inline int hpet_enable(void) { return 0; }
+static inline int hpet_enable(int early_call) { return 0; }
#endif /* CONFIG_HPET_TIMER */
#endif /* _I386_HPET_H */
Index: linux-2.6.21/arch/i386/kernel/time.c
===================================================================
--- linux-2.6.21.orig/arch/i386/kernel/time.c 2007-04-27 15:27:12.000000000 -0700
+++ linux-2.6.21/arch/i386/kernel/time.c 2007-04-27 15:30:22.000000000 -0700
@@ -264,7 +264,7 @@
/* Duplicate of time_init() below, with hpet_enable part added */
void __init hpet_time_init(void)
{
- if (!hpet_enable())
+ if (!hpet_enable(1))
setup_pit_timer();
time_init_hook();
}
Index: linux-2.6.21/arch/i386/kernel/hpet.c
===================================================================
--- linux-2.6.21.orig/arch/i386/kernel/hpet.c 2007-04-27 15:30:15.000000000 -0700
+++ linux-2.6.21/arch/i386/kernel/hpet.c 2007-04-27 15:30:22.000000000 -0700
@@ -51,6 +51,8 @@
if (str) {
if (!strncmp("disable", str, 7))
boot_hpet_disable = 1;
+ else if (!strncmp("standard", str, 9))
+ hpet_preferred_int_mode = HPET_INT_STD;
}
return 1;
}
@@ -723,13 +725,16 @@
/*
* Try to setup the HPET timer
*/
-int __init hpet_enable(void)
+int __init hpet_enable(int early_call)
{
unsigned long id;
if (hpet_virt_address)
return 0;
+ if (early_call && hpet_preferred_int_mode == HPET_INT_STD)
+ return 0;
+
if (!is_hpet_capable())
return 0;
@@ -784,13 +789,15 @@
if (boot_hpet_disable)
return -ENODEV;
- if (!hpet_address) {
- if (!force_hpet_address)
- return -ENODEV;
+ if (!hpet_virt_address) {
+ if (!hpet_address) {
+ if (!force_hpet_address)
+ return -ENODEV;
- hpet_address = force_hpet_address;
+ hpet_address = force_hpet_address;
+ }
hpet_preferred_int_mode = HPET_INT_STD;
- ret = hpet_enable();
+ ret = hpet_enable(0);
if (ret < 0 || !hpet_virt_address)
return -ENODEV;
}
Index: linux-2.6.21/Documentation/kernel-parameters.txt
===================================================================
--- linux-2.6.21.orig/Documentation/kernel-parameters.txt 2007-04-25 20:08:32.000000000 -0700
+++ linux-2.6.21/Documentation/kernel-parameters.txt 2007-04-27 15:31:31.000000000 -0700
@@ -384,8 +384,8 @@
over the 8254 in addition to over the IO-APIC. The
kernel tries to set a sensible default.
- hpet= [IA-32,HPET] option to disable HPET and use PIT.
- Format: disable
+ hpet= [IA-32,HPET] option to choose HPET modes.
+ Format: {disable | standard}
cm206= [HW,CD]
Format: { auto | [<io>,][<irq>] }
-
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