x86: powernow-k8: ignore out-of-range PstateStatus value

PATCH New Andreas Herrmann 2 participants 6 messages Nov 7, 2008 – Nov 21, 2008 x86

Share & tools

Andreas Herrmann

author

2008-11-07 15:10 UTC #0 lore raw

PATCH 1/1 x86: powernow-k8: ignore out-of-range PstateStatus value

A workaround for AMD CPU family 11h erratum 311 might cause that the P-state Status Register shows a "current P-state" which is larger than the "current P-state limit" in P-state Current Limit Register. For the wrong P-state value there is no ACPI _PSS object defined and powernow-k8/cpufreq can't determine the proper CPU frequency for that state.

As a consequence this can cause a panic during boot (potentially with all recent kernel versions -- at least I have reproduced it with various 2.6.27 kernels and with the current .28 series), as an example:

powernow-k8: Found 1 AMD Turion(tm)X2 Ultra DualCore Mobile ZM-82 processors (2 \
)

powernow-k8:    0 : pstate 0 (2200 MHz)
powernow-k8:    1 : pstate 1 (1100 MHz)
powernow-k8:    2 : pstate 2 (600 MHz)
BUG: unable to handle kernel paging request at ffff88086e7528b8
IP: [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
PGD 202063 PUD 0
Oops: 0002 [#1] SMP
last sysfs file:
CPU 1
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.28-rc3-dirty #16
RIP: 0010:[<ffffffff80486361>]  [<ffffffff80486361>] cpufreq_stats_update+0x4a/0\
f
Synaptics claims to have extended capabilities, but I'm not able to read them.<6\
6
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88006e7528c0
RDX: 00000000ffffffff RSI: ffff88006e54af00 RDI: ffffffff808f056c
RBP: 00000000fffee697 R08: 0000000000000003 R09: ffff88006e73f080
R10: 0000000000000001 R11: 00000000002191c0 R12: ffff88006fb83c10
R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88006fb50740(0000) knlGS:0000000000000000

Unable to initialize Synaptics hardware.
CS: 0010 DS: 0018 ES: 0018 CR0: 000000008005003b
CR2: ffff88086e7528b8 CR3: 0000000000201000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process swapper (pid: 1, threadinfo ffff88006fb82000, task ffff88006fb816d0)

Stack:
 ffff88006e74da50 0000000000000000 ffff88006e54af00 ffffffff804863c7
 ffff88006e74da50 0000000000000000 00000000ffffffff 0000000000000000
 ffff88006fb83c10 ffffffff8024b46c ffffffff808f0560 ffff88006fb83c10
Call Trace:
 [<ffffffff804863c7>] ? cpufreq_stat_notifier_trans+0x51/0x83
 [<ffffffff8024b46c>] ? notifier_call_chain+0x29/0x4c
 [<ffffffff8024b561>] ? __srcu_notifier_call_chain+0x46/0x61
 [<ffffffff8048496d>] ? cpufreq_notify_transition+0x93/0xa9
 [<ffffffff8021ab8d>] ? powernowk8_target+0x1e8/0x5f3
 [<ffffffff80486687>] ? cpufreq_governor_performance+0x1b/0x20
 [<ffffffff80484886>] ? __cpufreq_governor+0x71/0xa8
 [<ffffffff80484b21>] ? __cpufreq_set_policy+0x101/0x13e
 [<ffffffff80485bcd>] ? cpufreq_add_dev+0x3f0/0x4cd
 [<ffffffff8048577a>] ? handle_update+0x0/0x8
 [<ffffffff803c2062>] ? sysdev_driver_register+0xb6/0x10d
 [<ffffffff8056592c>] ? powernowk8_init+0x0/0x7e
 [<ffffffff8048604c>] ? cpufreq_register_driver+0x8f/0x140
 [<ffffffff80209056>] ? _stext+0x56/0x14f
 [<ffffffff802c2234>] ? proc_register+0x122/0x17d
 [<ffffffff802c23a0>] ? create_proc_entry+0x73/0x8a
 [<ffffffff8025c259>] ? register_irq_proc+0x92/0xaa
 [<ffffffff8025c2c8>] ? init_irq_proc+0x57/0x69
 [<ffffffff807fc85f>] ? kernel_init+0x116/0x169
 [<ffffffff8020cc79>] ? child_rip+0xa/0x11
 [<ffffffff807fc749>] ? kernel_init+0x0/0x169
 [<ffffffff8020cc6f>] ? child_rip+0x0/0x11
Code: 05 c5 83 36 00 48 c7 c2 48 5d 86 80 48 8b 04 d8 48 8b 40 08 48 8b 34 02 48\

RIP [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
RSP <ffff88006fb83b20>
CR2: ffff88086e7528b8

---[ end trace 0678bac75e67a2f7 ]---
Kernel panic - not syncing: Attempted to kill init!

In short, aftereffect of the wrong P-state is that cpufreq_stats_update() uses "-1" as index for some array in

cpufreq_stats_update (unsigned int cpu)
{
...

     if (stat->time_in_state)
                stat->time_in_state[stat->last_index] =
                        cputime64_add(stat->time_in_state[stat->last_index],
                                      cputime_sub(cur_time, stat->last_time));

...
}

Fortunately, the wrong P-state value is returned only if the core is in P-state 0. This fix solves the problem by detecting the out-of-range P-state, ignoring it, and using "0" instead.

Cc [email protected]

Acked-by Mark Langsdorf <[email protected]>

Signed-off-by Andreas Herrmann <[email protected]>

---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c |   16 +++++++++++++---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.h |    4 +++-
 2 files changed, 16 insertions(+), 4 deletions(-)

Patch is against today's Linus' git (v2.6.28-rc3-195-g4bab0ea). Please apply.

Thanks,
Andreas

arch/x86/kernel/cpu/cpufreq/powernow-k8.c +13 -3

index d3dcd58..8c76905 100644
@@ -115,9 +115,18 @@ static int query_current_values_with_pending_wait(struct powernow_k8_data *data)
 	u32 i = 0;
 
 	if (cpu_family == CPU_HW_PSTATE) {
-		rdmsr(MSR_PSTATE_STATUS, lo, hi);
-		i = lo & HW_PSTATE_MASK;
-		data->currpstate = i;
+		if (data->currpstate == INVALID_HW_PSTATE) {
+			/* read (initial) hw pstate if not yet set */
+			rdmsr(MSR_PSTATE_STATUS, lo, hi);
+			i = lo & HW_PSTATE_MASK;
+
+			/* a workaround for family 11h erratum 311 might cause
+			   an "out-of-range Pstate if the core is in Pstate-0 */
+			if (i >= data->numps)
+				data->currpstate = 0;
+			else
+				data->currpstate = i;
+		}
 		return 0;
 	}
 	do {

@@ -1121,6 +1130,7 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
 	}
 
 	data->cpu = pol->cpu;
+	data->currpstate = INVALID_HW_PSTATE;
 
 	if (powernow_k8_cpu_init_acpi(data)) {
 		/*

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +3 -1

index ab48cfe..4078f5d 100644
@@ -23,7 +23,9 @@ struct powernow_k8_data {
         u32 exttype; /* extended interface = 1 */
 
 	/* keep track of the current fid / vid or pstate */
-	u32 currvid, currfid, currpstate;
+	u32 currvid, currfid;
+	u32 currpstate;
+#define INVALID_HW_PSTATE 0xff
 
 	/* the powernow_table includes all frequency and vid/fid pairings:
 	 * fid are the lower 8 bits of the index, vid are the upper 8 bits.

Signature · 1 line

1.6.0.3

Andreas Herrmann

author

2008-11-21 08:10 UTC #1 lore raw

PATCH 1/1 x86: powernow-k8: ignore out-of-range PstateStatus value

powernow-k8: Found 1 AMD Turion(tm)X2 Ultra DualCore Mobile ZM-82 processors (2 \
)

powernow-k8:    0 : pstate 0 (2200 MHz)
powernow-k8:    1 : pstate 1 (1100 MHz)
powernow-k8:    2 : pstate 2 (600 MHz)
BUG: unable to handle kernel paging request at ffff88086e7528b8
IP: [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
PGD 202063 PUD 0
Oops: 0002 [#1] SMP
last sysfs file:
CPU 1
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.28-rc3-dirty #16
RIP: 0010:[<ffffffff80486361>]  [<ffffffff80486361>] cpufreq_stats_update+0x4a/0\
f
Synaptics claims to have extended capabilities, but I'm not able to read them.<6\
6
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88006e7528c0
RDX: 00000000ffffffff RSI: ffff88006e54af00 RDI: ffffffff808f056c
RBP: 00000000fffee697 R08: 0000000000000003 R09: ffff88006e73f080
R10: 0000000000000001 R11: 00000000002191c0 R12: ffff88006fb83c10
R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88006fb50740(0000) knlGS:0000000000000000

Stack:
 ffff88006e74da50 0000000000000000 ffff88006e54af00 ffffffff804863c7
 ffff88006e74da50 0000000000000000 00000000ffffffff 0000000000000000
 ffff88006fb83c10 ffffffff8024b46c ffffffff808f0560 ffff88006fb83c10
Call Trace:
 [<ffffffff804863c7>] ? cpufreq_stat_notifier_trans+0x51/0x83
 [<ffffffff8024b46c>] ? notifier_call_chain+0x29/0x4c
 [<ffffffff8024b561>] ? __srcu_notifier_call_chain+0x46/0x61
 [<ffffffff8048496d>] ? cpufreq_notify_transition+0x93/0xa9
 [<ffffffff8021ab8d>] ? powernowk8_target+0x1e8/0x5f3
 [<ffffffff80486687>] ? cpufreq_governor_performance+0x1b/0x20
 [<ffffffff80484886>] ? __cpufreq_governor+0x71/0xa8
 [<ffffffff80484b21>] ? __cpufreq_set_policy+0x101/0x13e
 [<ffffffff80485bcd>] ? cpufreq_add_dev+0x3f0/0x4cd
 [<ffffffff8048577a>] ? handle_update+0x0/0x8
 [<ffffffff803c2062>] ? sysdev_driver_register+0xb6/0x10d
 [<ffffffff8056592c>] ? powernowk8_init+0x0/0x7e
 [<ffffffff8048604c>] ? cpufreq_register_driver+0x8f/0x140
 [<ffffffff80209056>] ? _stext+0x56/0x14f
 [<ffffffff802c2234>] ? proc_register+0x122/0x17d
 [<ffffffff802c23a0>] ? create_proc_entry+0x73/0x8a
 [<ffffffff8025c259>] ? register_irq_proc+0x92/0xaa
 [<ffffffff8025c2c8>] ? init_irq_proc+0x57/0x69
 [<ffffffff807fc85f>] ? kernel_init+0x116/0x169
 [<ffffffff8020cc79>] ? child_rip+0xa/0x11
 [<ffffffff807fc749>] ? kernel_init+0x0/0x169
 [<ffffffff8020cc6f>] ? child_rip+0x0/0x11
Code: 05 c5 83 36 00 48 c7 c2 48 5d 86 80 48 8b 04 d8 48 8b 40 08 48 8b 34 02 48\

RIP [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
RSP <ffff88006fb83b20>
CR2: ffff88086e7528b8

---[ end trace 0678bac75e67a2f7 ]---
Kernel panic - not syncing: Attempted to kill init!

In short, aftereffect of the wrong P-state is that cpufreq_stats_update() uses "-1" as index for some array in

cpufreq_stats_update (unsigned int cpu)
{
...

     if (stat->time_in_state)
                stat->time_in_state[stat->last_index] =
                        cputime64_add(stat->time_in_state[stat->last_index],
                                      cputime_sub(cur_time, stat->last_time));

...
}

Fortunately, the wrong P-state value is returned only if the core is in P-state 0. This fix solves the problem by detecting the out-of-range P-state, ignoring it, and using "0" instead.

Cc [email protected]

Acked-by Mark Langsdorf <[email protected]>

Signed-off-by Andreas Herrmann <[email protected]>

---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c |   16 +++++++++++++---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.h |    4 +++-
 2 files changed, 16 insertions(+), 4 deletions(-)

Linus,

please apply for .28.

Thanks,

Andreas

arch/x86/kernel/cpu/cpufreq/powernow-k8.c +13 -3

index d3dcd58..8c76905 100644
@@ -115,9 +115,18 @@ static int query_current_values_with_pending_wait(struct powernow_k8_data *data)
 	u32 i = 0;
 
 	if (cpu_family == CPU_HW_PSTATE) {
-		rdmsr(MSR_PSTATE_STATUS, lo, hi);
-		i = lo & HW_PSTATE_MASK;
-		data->currpstate = i;
+		if (data->currpstate == INVALID_HW_PSTATE) {
+			/* read (initial) hw pstate if not yet set */
+			rdmsr(MSR_PSTATE_STATUS, lo, hi);
+			i = lo & HW_PSTATE_MASK;
+
+			/* a workaround for family 11h erratum 311 might cause
+			   an "out-of-range Pstate if the core is in Pstate-0 */
+			if (i >= data->numps)
+				data->currpstate = 0;
+			else
+				data->currpstate = i;
+		}
 		return 0;
 	}
 	do {

@@ -1121,6 +1130,7 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
 	}
 
 	data->cpu = pol->cpu;
+	data->currpstate = INVALID_HW_PSTATE;
 
 	if (powernow_k8_cpu_init_acpi(data)) {
 		/*

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +3 -1

index ab48cfe..4078f5d 100644
@@ -23,7 +23,9 @@ struct powernow_k8_data {
         u32 exttype; /* extended interface = 1 */
 
 	/* keep track of the current fid / vid or pstate */
-	u32 currvid, currfid, currpstate;
+	u32 currvid, currfid;
+	u32 currpstate;
+#define INVALID_HW_PSTATE 0xff
 
 	/* the powernow_table includes all frequency and vid/fid pairings:
 	 * fid are the lower 8 bits of the index, vid are the upper 8 bits.

Signature · 1 line

1.6.0.3

Ingo Molnar

2008-11-21 08:24 UTC #2 lore raw

nice fix! A few minor nits:

arch/x86/kernel/cpu/cpufreq/powernow-k8.c static int query_current_values_with_pending_wait(struct powernow_k8_data *data) · line 124

Quoted 2 lines

arch/x86/kernel/cpu/cpufreq/powernow-k8.c +2 -0

+			/* a workaround for family 11h erratum 311 might cause
+			   an "out-of-range Pstate if the core is in Pstate-0 */

Please use the customary comment style:

/*
* Comment .....
* ...... goes here:
*/

and since it's multi-line anyway, keep to the 80-col limit too please.

arch/x86/kernel/cpu/cpufreq/powernow-k8.h struct powernow_k8_data { · line 27

Quoted 11 lines

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +2 -1

index ab48cfe..4078f5d 100644
@@ -23,7 +23,9 @@ struct powernow_k8_data {
         u32 exttype; /* extended interface = 1 */
 
 	/* keep track of the current fid / vid or pstate */
-	u32 currvid, currfid, currpstate;
+	u32 currvid, currfid;
+	u32 currpstate;

Any reason why it has been moved to a separate line? (either split all fields or keep them all together)

arch/x86/kernel/cpu/cpufreq/powernow-k8.h struct powernow_k8_data { · line 28

Quoted 1 line

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +1 -0
+#define INVALID_HW_PSTATE 0xff

Please use an enum, not a define in the middle of a struct.

Thanks,

Ingo

Andreas Herrmann

author

2008-11-21 13:17 UTC #3 lore raw

Quoted 11 lines · Ingo Molnar

nice fix! A few minor nits:
arch/x86/kernel/cpu/cpufreq/powernow-k8.c static int query_current_values_with_pending_wait(struct powernow_k8_data *data) · line 124
Quoted 2 lines
arch/x86/kernel/cpu/cpufreq/powernow-k8.c +2 -0
+			/* a workaround for family 11h erratum 311 might cause
+			   an "out-of-range Pstate if the core is in Pstate-0 */
Please use the customary comment style:
/*
* Comment .....
* ...... goes here:
   */

I don't prefer that style -- but if you do.

Quoted 1 line

and since it's multi-line anyway, keep to the 80-col limit too please.

2nd line should be exactly 80 columns.

Quoted 7 lines

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +0 -0

index ab48cfe..4078f5d 100644
@@ -23,7 +23,9 @@ struct powernow_k8_data {
         u32 exttype; /* extended interface = 1 */

Quoted 6 lines

arch/x86/kernel/cpu/cpufreq/powernow-k8.h struct powernow_k8_data { · line 27
Quoted 4 lines
arch/x86/kernel/cpu/cpufreq/powernow-k8.h +2 -1
 	/* keep track of the current fid / vid or pstate */
-	u32 currvid, currfid, currpstate;
+	u32 currvid, currfid;
+	u32 currpstate;
Any reason why it has been moved to a separate line?

Sure, it's to emphasize that the following define is just for this field.

Andreas

Ingo Molnar

2008-11-21 15:13 UTC #4 lore raw

Quoted 13 lines · Andreas Herrmann

Quoted 11 lines · Ingo Molnar
nice fix! A few minor nits:
arch/x86/kernel/cpu/cpufreq/powernow-k8.c static int query_current_values_with_pending_wait(struct powernow_k8_data *data) · line 124
Quoted 2 lines
arch/x86/kernel/cpu/cpufreq/powernow-k8.c +2 -0
+			/* a workaround for family 11h erratum 311 might cause
+			   an "out-of-range Pstate if the core is in Pstate-0 */
Please use the customary comment style:
/*
* Comment .....
* ...... goes here:
   */

Quoted 1 line

I don't prefer that style -- but if you do.

it's not about my or your preference. It's about what we all do in the kernel, documented in Documentation/CodingStyle:

| The preferred style for long (multi-line) comments is:
|
|        /*
|         * This is the preferred style for multi-line
|         * comments in the Linux kernel source code.
|         * Please use it consistently.
|         *
|         * Description:  A column of asterisks on the left side,
|         * with beginning and ending almost-blank lines.
|         */

Ingo

Andreas Herrmann

author

2008-11-21 13:51 UTC #5 lore raw

PATCH v2 1/1 x86: powernow-k8: ignore out-of-range PstateStatus value

In reply to Ingo Molnar

powernow-k8: Found 1 AMD Turion(tm)X2 Ultra DualCore Mobile ZM-82 processors (2 \
)

powernow-k8:    0 : pstate 0 (2200 MHz)
powernow-k8:    1 : pstate 1 (1100 MHz)
powernow-k8:    2 : pstate 2 (600 MHz)
BUG: unable to handle kernel paging request at ffff88086e7528b8
IP: [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
PGD 202063 PUD 0
Oops: 0002 [#1] SMP
last sysfs file:
CPU 1
Modules linked in:
Pid: 1, comm: swapper Not tainted 2.6.28-rc3-dirty #16
RIP: 0010:[<ffffffff80486361>]  [<ffffffff80486361>] cpufreq_stats_update+0x4a/0\
f
Synaptics claims to have extended capabilities, but I'm not able to read them.<6\
6
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88006e7528c0
RDX: 00000000ffffffff RSI: ffff88006e54af00 RDI: ffffffff808f056c
RBP: 00000000fffee697 R08: 0000000000000003 R09: ffff88006e73f080
R10: 0000000000000001 R11: 00000000002191c0 R12: ffff88006fb83c10
R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88006fb50740(0000) knlGS:0000000000000000

Stack:
 ffff88006e74da50 0000000000000000 ffff88006e54af00 ffffffff804863c7
 ffff88006e74da50 0000000000000000 00000000ffffffff 0000000000000000
 ffff88006fb83c10 ffffffff8024b46c ffffffff808f0560 ffff88006fb83c10
Call Trace:
 [<ffffffff804863c7>] ? cpufreq_stat_notifier_trans+0x51/0x83
 [<ffffffff8024b46c>] ? notifier_call_chain+0x29/0x4c
 [<ffffffff8024b561>] ? __srcu_notifier_call_chain+0x46/0x61
 [<ffffffff8048496d>] ? cpufreq_notify_transition+0x93/0xa9
 [<ffffffff8021ab8d>] ? powernowk8_target+0x1e8/0x5f3
 [<ffffffff80486687>] ? cpufreq_governor_performance+0x1b/0x20
 [<ffffffff80484886>] ? __cpufreq_governor+0x71/0xa8
 [<ffffffff80484b21>] ? __cpufreq_set_policy+0x101/0x13e
 [<ffffffff80485bcd>] ? cpufreq_add_dev+0x3f0/0x4cd
 [<ffffffff8048577a>] ? handle_update+0x0/0x8
 [<ffffffff803c2062>] ? sysdev_driver_register+0xb6/0x10d
 [<ffffffff8056592c>] ? powernowk8_init+0x0/0x7e
 [<ffffffff8048604c>] ? cpufreq_register_driver+0x8f/0x140
 [<ffffffff80209056>] ? _stext+0x56/0x14f
 [<ffffffff802c2234>] ? proc_register+0x122/0x17d
 [<ffffffff802c23a0>] ? create_proc_entry+0x73/0x8a
 [<ffffffff8025c259>] ? register_irq_proc+0x92/0xaa
 [<ffffffff8025c2c8>] ? init_irq_proc+0x57/0x69
 [<ffffffff807fc85f>] ? kernel_init+0x116/0x169
 [<ffffffff8020cc79>] ? child_rip+0xa/0x11
 [<ffffffff807fc749>] ? kernel_init+0x0/0x169
 [<ffffffff8020cc6f>] ? child_rip+0x0/0x11
Code: 05 c5 83 36 00 48 c7 c2 48 5d 86 80 48 8b 04 d8 48 8b 40 08 48 8b 34 02 48\

RIP [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
RSP <ffff88006fb83b20>
CR2: ffff88086e7528b8

---[ end trace 0678bac75e67a2f7 ]---
Kernel panic - not syncing: Attempted to kill init!

In short, aftereffect of the wrong P-state is that cpufreq_stats_update() uses "-1" as index for some array in

cpufreq_stats_update (unsigned int cpu)
{
...

     if (stat->time_in_state)
                stat->time_in_state[stat->last_index] =
                        cputime64_add(stat->time_in_state[stat->last_index],
                                      cputime_sub(cur_time, stat->last_time));

...
}

Fortunately, the wrong P-state value is returned only if the core is in P-state 0. This fix solves the problem by detecting the out-of-range P-state, ignoring it, and using "0" instead.

Cc Mark Langsdorf <[email protected]>

Signed-off-by Andreas Herrmann <[email protected]>

---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.c |   18 +++++++++++++++---
 arch/x86/kernel/cpu/cpufreq/powernow-k8.h |   17 ++++++++++++++++-
 2 files changed, 31 insertions(+), 4 deletions(-)

Ingo,

New patch -- addressing your comments.

Will you apply it, or will Linus do it? (In the end it's important that it goes into .28.)

Thanks,

Andreas

arch/x86/kernel/cpu/cpufreq/powernow-k8.c +15 -3

index d3dcd58..7f05f44 100644
@@ -115,9 +115,20 @@ static int query_current_values_with_pending_wait(struct powernow_k8_data *data)
 	u32 i = 0;
 
 	if (cpu_family == CPU_HW_PSTATE) {
-		rdmsr(MSR_PSTATE_STATUS, lo, hi);
-		i = lo & HW_PSTATE_MASK;
-		data->currpstate = i;
+		if (data->currpstate == HW_PSTATE_INVALID) {
+			/* read (initial) hw pstate if not yet set */
+			rdmsr(MSR_PSTATE_STATUS, lo, hi);
+			i = lo & HW_PSTATE_MASK;
+
+			/*
+			 * a workaround for family 11h erratum 311 might cause
+			 * an "out-of-range Pstate if the core is in Pstate-0
+			 */
+			if (i >= data->numps)
+				data->currpstate = HW_PSTATE_0;
+			else
+				data->currpstate = i;
+		}
 		return 0;
 	}
 	do {

@@ -1121,6 +1132,7 @@ static int __cpuinit powernowk8_cpu_init(struct cpufreq_policy *pol)
 	}
 
 	data->cpu = pol->cpu;
+	data->currpstate = HW_PSTATE_INVALID;
 
 	if (powernow_k8_cpu_init_acpi(data)) {
 		/*

arch/x86/kernel/cpu/cpufreq/powernow-k8.h +16 -1

index ab48cfe..65cfb5d 100644
@@ -5,6 +5,19 @@
  *  http://www.gnu.org/licenses/gpl.html
  */
 
+
+enum pstate {
+	HW_PSTATE_INVALID = 0xff,
+	HW_PSTATE_0 = 0,
+	HW_PSTATE_1 = 1,
+	HW_PSTATE_2 = 2,
+	HW_PSTATE_3 = 3,
+	HW_PSTATE_4 = 4,
+	HW_PSTATE_5 = 5,
+	HW_PSTATE_6 = 6,
+	HW_PSTATE_7 = 7,
+};
+
 struct powernow_k8_data {
 	unsigned int cpu;

@@ -23,7 +36,9 @@ struct powernow_k8_data {
         u32 exttype; /* extended interface = 1 */
 
 	/* keep track of the current fid / vid or pstate */
-	u32 currvid, currfid, currpstate;
+	u32 currvid;
+	u32 currfid;
+	enum pstate currpstate;
 
 	/* the powernow_table includes all frequency and vid/fid pairings:
 	 * fid are the lower 8 bits of the index, vid are the upper 8 bits.

Signature · 1 line

1.6.0.4