2.6.33: Problem continues: WARNING: at arch/x86/kernel/hpet.c:404 hpet_next_event+0x70/0x80
Justin Piszcz
Again, on the Intel DP55KG board:
# uname -a
Linux host 2.6.33 #1 SMP Wed Feb 24 18:31:00 EST 2010 x86_64 GNU/Linux
[ 1.237600] ------------[ cut here ]------------
[ 1.237890] WARNING: at arch/x86/kernel/hpet.c:404 hpet_next_event+0x70/0x80()
[ 1.238221] Hardware name:
[ 1.238504] hpet: compare register read back failed.
[ 1.238793] Modules linked in:
[ 1.239315] Pid: 0, comm: swapper Not tainted 2.6.33 #1
[ 1.239605] Call Trace:
[ 1.239886] <IRQ> [<ffffffff81056c13>] ? warn_slowpath_common+0x73/0xb0
[ 1.240409] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
[ 1.240699] [<ffffffff81056cb0>] ? warn_slowpath_fmt+0x40/0x50
[ 1.240992] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
[ 1.241281] [<ffffffff81041ad0>] ? hpet_next_event+0x70/0x80
[ 1.241573] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
[ 1.241859] [<ffffffff81078e32>] ? tick_handle_oneshot_broadcast+0xe2/0x100
[ 1.246533] [<ffffffff8102a67a>] ? timer_interrupt+0x1a/0x30
[ 1.246826] [<ffffffff81085499>] ? handle_IRQ_event+0x39/0xd0
[ 1.247118] [<ffffffff81087368>] ? handle_edge_irq+0xb8/0x160
[ 1.247407] [<ffffffff81029f55>] ? handle_irq+0x15/0x20
[ 1.247689] [<ffffffff810294a2>] ? do_IRQ+0x62/0xe0
[ 1.247976] [<ffffffff8146be53>] ? ret_from_intr+0x0/0xa
[ 1.248262] <EOI> [<ffffffff8102f277>] ? mwait_idle+0x57/0x80
[ 1.248796] [<ffffffff8102645c>] ? cpu_idle+0x5c/0xb0
[ 1.249080] ---[ end trace db7f668fb6fef4e1 ]---
Is this something Intel has to fix or is it a bug in the kernel?
Justin.
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Thomas Backlund
Justin Piszcz
Hi,
This looks like what I want, will it be included in 2.6.33.1 or 2.6.34?
Justin.
Pallipadi, Venkatesh
This is a chipset erratum.
Thomas: You mentioned we can retain this check only for known-buggy and
hpet debug kind of options. But here is the simple workaround patch for
this particular erratum.
x86: Erratum workaround for read after write of HPET comparator
Some chipsets have a erratum due to which read immediately following a
write of HPET comparator returns old comparator value instead of most
recently written value.
Erratum 15 in
"Intel I/O Controller Hub 9 (ICH9) Family Specification Update"
(http://www.intel.com/assets/pdf/specupdate/316973.pdf)
Workaround for the errata is to read the comparator twice if the first
one fails.
Signed-off-by: Venkatesh Pallipadi <venkatesh...@intel.com>
---
arch/x86/kernel/hpet.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ad80a1c..7b0dd63 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -399,9 +399,15 @@ static int hpet_next_event(unsigned long delta,
* 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.
*/
- WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,
+ 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");
+ }
return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
}
--
1.6.0.6
Thomas Gleixner
Yes, that'd be the preferred way. I need to find the box which had the
problem (ATI chipset) and force the readback for that one. That saves
all other machines the extra hardware access.
Thanks,
tglx
tip-bot for Pallipadi, Venkatesh
Gitweb: http://git.kernel.org/tip/8da854cb02156c90028233ae1e85ce46a1d3f82c
Author: Pallipadi, Venkatesh <venkatesh...@intel.com>
AuthorDate: Thu, 25 Feb 2010 10:53:48 -0800
Committer: H. Peter Anvin <h...@zytor.com>
CommitDate: Thu, 1 Apr 2010 15:21:47 -0700
x86, hpet: Erratum workaround for read after write of HPET comparator
Some chipsets have a erratum due to which read immediately following a
write of HPET comparator returns old comparator value instead of most
recently written value.
Erratum 15 in
"Intel I/O Controller Hub 9 (ICH9) Family Specification Update"
(http://www.intel.com/assets/pdf/specupdate/316973.pdf)
Workaround for the errata is to read the comparator twice if the first
one fails.
Signed-off-by: Venkatesh Pallipadi <venkatesh...@intel.com>
LKML-Reference: <2010022518...@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <h...@zytor.com>
Cc: Venkatesh Pallipadi <venkatesh...@gmail.com>
Cc: <sta...@kernel.org>
---
arch/x86/kernel/hpet.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index ee4fa1b..3d422da 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -399,9 +399,15 @@ static int hpet_next_event(unsigned long delta,
* 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.
*/
- WARN_ONCE(hpet_readl(HPET_Tn_CMP(timer)) != cnt,
+ 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");
+ }
return (s32)(hpet_readl(HPET_COUNTER) - cnt) >= 0 ? -ETIME : 0;
}
--
tip-bot for Thomas Gleixner
Gitweb: http://git.kernel.org/tip/30a564be9d9554c168a654eddc2165869cc0d7bf
Author: Thomas Gleixner <tg...@linutronix.de>
AuthorDate: Tue, 13 Apr 2010 15:31:36 +0200CommitDate: Wed, 28 Apr 2010 18:14:29 -0700
x86, hpet: Restrict read back to affected ATI chipsets
After programming the HPET, we do a readback as a workaround for
ATI/SBx00 chipsets as a synchronization. Unfortunately this triggers
an erratum in newer ICH chipsets (ICH9+) where reading the comparator
immediately after the write returns the old value. Furthermore, as
always, I/O reads are bad for performance.
Therefore, restrict the readback to the chipsets that need it, or, for
debugging purposes, when we are running with hpet=verbose.
Signed-off-by: Thomas Gleixner <tg...@linutronix.de>
Acked-by: Venkatesh Pallipadi <ve...@google.com>
LKML-Reference: <2010022518...@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <h...@zytor.com>
---
arch/x86/include/asm/hpet.h | 1 +
arch/x86/kernel/hpet.c | 29 +++++++++++++++++------------
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 1d5c08a..004e6e2 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 23b4ecd..a198b7c 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 12e9fea..cd2c336 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,