diff options
| -rw-r--r-- | arch/x86/include/asm/hpet.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/hpet.c | 29 | ||||
| -rw-r--r-- | arch/x86/kernel/quirks.c | 5 |
3 files changed, 23 insertions, 12 deletions
diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h index 1d5c08a1bdfd..004e6e25e913 100644 --- a/arch/x86/include/asm/hpet.h +++ b/arch/x86/include/asm/hpet.h @@ -68,6 +68,7 @@ extern unsigned long force_hpet_address; extern u8 hpet_blockid; extern int hpet_force_user; extern u8 hpet_msi_disable; +extern u8 hpet_readback_cmp; extern int is_hpet_enabled(void); extern int hpet_enable(void); extern void hpet_disable(void); diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c index 23b4ecdffa9b..a198b7c87a12 100644 --- a/arch/x86/kernel/hpet.c +++ b/arch/x86/kernel/hpet.c @@ -36,6 +36,7 @@ unsigned long hpet_address; u8 hpet_blockid; /* OS timer block num */ u8 hpet_msi_disable; +u8 hpet_readback_cmp; #ifdef CONFIG_PCI_MSI static unsigned long hpet_num_timers; @@ -395,19 +396,23 @@ static int hpet_next_event(unsigned long delta, * at that point and we would wait for the next hpet interrupt * forever. We found out that reading the CMP register back * forces the transfer so we can rely on the comparison with - * the counter register below. If the read back from the - * compare register does not match the value we programmed - * then we might have a real hardware problem. We can not do - * much about it here, but at least alert the user/admin with - * a prominent warning. - * An erratum on some chipsets (ICH9,..), results in comparator read - * immediately following a write returning old value. Workaround - * for this is to read this value second time, when first - * read returns old value. + * the counter register below. + * + * That works fine on those ATI chipsets, but on newer Intel + * chipsets (ICH9...) this triggers due to an erratum: Reading + * the comparator immediately following a write is returning + * the old value. + * + * We restrict the read back to the affected ATI chipsets (set + * by quirks) and also run it with hpet=verbose for debugging + * purposes. */ - if (unlikely((u32)hpet_readl(HPET_Tn_CMP(timer)) != cnt)) { - WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt, - KERN_WARNING "hpet: compare register read back failed.\n"); + if (hpet_readback_cmp || hpet_verbose) { + u32 cmp = hpet_readl(HPET_Tn_CMP(timer)); + + if (cmp != cnt) + printk_once(KERN_WARNING + "hpet: compare register read back failed.\n"); } return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0; diff --git a/arch/x86/kernel/quirks.c b/arch/x86/kernel/quirks.c index 12e9feaa2f7a..cd2c336c8d09 100644 --- a/arch/x86/kernel/quirks.c +++ b/arch/x86/kernel/quirks.c @@ -495,10 +495,15 @@ void force_hpet_resume(void) /* * HPET MSI on some boards (ATI SB700/SB800) has side effect on * floppy DMA. Disable HPET MSI on such platforms. + * + * Also force the read back of the CMP register in hpet_next_event() + * to work around the problem that the CMP register write seems to be + * delayed. See hpet_next_event() for details. */ static void force_disable_hpet_msi(struct pci_dev *unused) { hpet_msi_disable = 1; + hpet_readback_cmp = 1; } DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_ATI, PCI_DEVICE_ID_ATI_SBX00_SMBUS, |