[PATCH 0/5] powerpc/tau: TAU driver fixes

[PATCH 0/5] powerpc/tau: TAU driver fixes

[Finn Thain]

This patch series fixes various bugs in the Thermal Assist Unit driver.
It was tested on 266 MHz and 292 MHz PowerBook G3 laptops.


Finn Thain (5):
  powerpc/tau: Use appropriate temperature sample interval
  powerpc/tau: Convert from timer to workqueue
  powerpc/tau: Remove duplicated set_thresholds() call
  powerpc/tau: Check processor type before enabling TAU interrupt
  powerpc/tau: Disable TAU between measurements

 arch/powerpc/include/asm/reg.h |   2 +-
 arch/powerpc/kernel/tau_6xx.c  | 147 +++++++++++++--------------------
 arch/powerpc/platforms/Kconfig |  14 +---
 3 files changed, 62 insertions(+), 101 deletions(-)

-- 
2.26.2

[PATCH 1/5] powerpc/tau: Use appropriate temperature sample interval

[Finn Thain]

According to the MPC750 Users Manual, the SITV value in Thermal
Management Register 3 is 13 bits long. The present code calculates the
SITV value as 60 * 500 cycles. This would overflow to give 10 us on
a 500 MHz CPU rather than the intended 60 us. (But according to the
Microprocessor Datasheet, there is also a factor of 266 that has to be
applied to this value on certain parts i.e. speed sort above 266 MHz.)
Always use the maximum cycle count, as recommended by the Datasheet.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 arch/powerpc/include/asm/reg.h |  2 +-
 arch/powerpc/kernel/tau_6xx.c  | 12 ++++--------
 2 files changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 88e6c78100d9b..c750afc62887c 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -815,7 +815,7 @@
 #define THRM1_TIN	(1 << 31)
 #define THRM1_TIV	(1 << 30)
 #define THRM1_THRES(x)	((x&0x7f)<<23)
-#define THRM3_SITV(x)	((x&0x3fff)<<1)
+#define THRM3_SITV(x)	((x & 0x1fff) << 1)
 #define THRM1_TID	(1<<2)
 #define THRM1_TIE	(1<<1)
 #define THRM1_V		(1<<0)
diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index e2ab8a111b693..976d5bc1b5176 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -178,15 +178,11 @@ static void tau_timeout(void * info)
 	 * complex sleep code needs to be added. One mtspr every time
 	 * tau_timeout is called is probably not a big deal.
 	 *
-	 * Enable thermal sensor and set up sample interval timer
-	 * need 20 us to do the compare.. until a nice 'cpu_speed' function
-	 * call is implemented, just assume a 500 mhz clock. It doesn't really
-	 * matter if we take too long for a compare since it's all interrupt
-	 * driven anyway.
-	 *
-	 * use a extra long time.. (60 us @ 500 mhz)
+	 * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
+	 * recommends that "the maximum value be set in THRM3 under all
+	 * conditions."
 	 */
-	mtspr(SPRN_THRM3, THRM3_SITV(500*60) | THRM3_E);
+	mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
 
 	local_irq_restore(flags);
 }
-- 
2.26.2

[PATCH 3/5] powerpc/tau: Remove duplicated set_thresholds() call

[Finn Thain]

The commentary at the call site seems to disagree with the code. The
conditional prevents calling set_thresholds() via the exception handler,
which appears to crash. Perhaps that's because it immediately triggers
another TAU exception. Anyway, calling set_thresholds() from TAUupdate()
is redundant because tau_timeout() does so.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 arch/powerpc/kernel/tau_6xx.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index 268205cc347da..b8d7e7d498e0a 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -110,11 +110,6 @@ static void TAUupdate(int cpu)
 #ifdef DEBUG
 	printk("grew = %d\n", tau[cpu].grew);
 #endif
-
-#ifndef CONFIG_TAU_INT /* tau_timeout will do this if not using interrupts */
-	set_thresholds(cpu);
-#endif
-
 }
 
 #ifdef CONFIG_TAU_INT
-- 
2.26.2

[PATCH 2/5] powerpc/tau: Convert from timer to workqueue

[Finn Thain]

Since commit 19dbdcb8039cf ("smp: Warn on function calls from softirq
context") the Thermal Assist Unit driver causes a warning like the
following when CONFIG_SMP is enabled.

------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at kernel/smp.c:428 smp_call_function_many_cond+0xf4/0x38c
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-pmac #3
NIP:  c00b37a8 LR: c00b3abc CTR: c001218c
REGS: c0799c60 TRAP: 0700   Not tainted  (5.7.0-pmac)
MSR:  00029032 <EE,ME,IR,DR,RI>  CR: 42000224  XER: 00000000

GPR00: c00b3abc c0799d18 c076e300 c079ef5c c0011fec 00000000 00000000 00000000
GPR08: 00000100 00000100 00008000 ffffffff 42000224 00000000 c079d040 c079d044
GPR16: 00000001 00000000 00000004 c0799da0 c079f054 c07a0000 c07a0000 00000000
GPR24: c0011fec 00000000 c079ef5c c079ef5c 00000000 00000000 00000000 00000000
NIP [c00b37a8] smp_call_function_many_cond+0xf4/0x38c
LR [c00b3abc] on_each_cpu+0x38/0x68
Call Trace:
[c0799d18] [ffffffff] 0xffffffff (unreliable)
[c0799d68] [c00b3abc] on_each_cpu+0x38/0x68
[c0799d88] [c0096704] call_timer_fn.isra.26+0x20/0x7c
[c0799d98] [c0096b40] run_timer_softirq+0x1d4/0x3fc
[c0799df8] [c05b4368] __do_softirq+0x118/0x240
[c0799e58] [c0039c44] irq_exit+0xc4/0xcc
[c0799e68] [c000ade8] timer_interrupt+0x1b0/0x230
[c0799ea8] [c0013520] ret_from_except+0x0/0x14
--- interrupt: 901 at arch_cpu_idle+0x24/0x6c
    LR = arch_cpu_idle+0x24/0x6c
[c0799f70] [00000001] 0x1 (unreliable)
[c0799f80] [c0060990] do_idle+0xd8/0x17c
[c0799fa0] [c0060ba8] cpu_startup_entry+0x24/0x28
[c0799fb0] [c072d220] start_kernel+0x434/0x44c
[c0799ff0] [00003860] 0x3860
Instruction dump:
8129f204 2f890000 40beff98 3d20c07a 8929eec4 2f890000 40beff88 0fe00000
81220000 552805de 550802ef 4182ff84 <0fe00000> 3860ffff 7f65db78 7f44d378
---[ end trace 34a886e47819c2eb ]---

Don't call on_each_cpu() from a timer callback, call it from a worker
thread instead.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 arch/powerpc/kernel/tau_6xx.c | 38 +++++++++++++++++------------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index 976d5bc1b5176..268205cc347da 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -13,13 +13,14 @@
  */
 
 #include <linux/errno.h>
-#include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/param.h>
 #include <linux/string.h>
 #include <linux/mm.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/workqueue.h>
 
 #include <asm/io.h>
 #include <asm/reg.h>
@@ -39,8 +40,6 @@ static struct tau_temp
 	unsigned char grew;
 } tau[NR_CPUS];
 
-struct timer_list tau_timer;
-
 #undef DEBUG
 
 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
@@ -50,7 +49,7 @@ struct timer_list tau_timer;
 #define step_size		2	/* step size when temp goes out of range */
 #define window_expand		1	/* expand the window by this much */
 /* configurable values for shrinking the window */
-#define shrink_timer	2*HZ	/* period between shrinking the window */
+#define shrink_timer	2000	/* period between shrinking the window */
 #define min_window	2	/* minimum window size, degrees C */
 
 static void set_thresholds(unsigned long cpu)
@@ -187,14 +186,18 @@ static void tau_timeout(void * info)
 	local_irq_restore(flags);
 }
 
-static void tau_timeout_smp(struct timer_list *unused)
-{
+static struct workqueue_struct *tau_workq;
 
-	/* schedule ourselves to be run again */
-	mod_timer(&tau_timer, jiffies + shrink_timer) ;
+static void tau_work_func(struct work_struct *work)
+{
+	msleep(shrink_timer);
 	on_each_cpu(tau_timeout, NULL, 0);
+	/* schedule ourselves to be run again */
+	queue_work(tau_workq, work);
 }
 
+DECLARE_WORK(tau_work, tau_work_func);
+
 /*
  * setup the TAU
  *
@@ -227,21 +230,16 @@ static int __init TAU_init(void)
 		return 1;
 	}
 
-
-	/* first, set up the window shrinking timer */
-	timer_setup(&tau_timer, tau_timeout_smp, 0);
-	tau_timer.expires = jiffies + shrink_timer;
-	add_timer(&tau_timer);
+	tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
+	if (!tau_workq)
+		return -ENOMEM;
 
 	on_each_cpu(TAU_init_smp, NULL, 0);
 
-	printk("Thermal assist unit ");
-#ifdef CONFIG_TAU_INT
-	printk("using interrupts, ");
-#else
-	printk("using timers, ");
-#endif
-	printk("shrink_timer: %d jiffies\n", shrink_timer);
+	queue_work(tau_workq, &tau_work);
+
+	pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
+		IS_ENABLED(CONFIG_TAU_INT) ? "interrupts" : "workqueue", shrink_timer);
 	tau_initialized = 1;
 
 	return 0;
-- 
2.26.2

[PATCH 4/5] powerpc/tau: Check processor type before enabling TAU interrupt

[Finn Thain]

According to Freescale's documentation, MPC74XX processors have an
erratum that prevents the TAU interrupt from working, so don't try to
use it when running on those processors.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 arch/powerpc/kernel/tau_6xx.c  | 33 ++++++++++++++-------------------
 arch/powerpc/platforms/Kconfig |  5 ++---
 2 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index b8d7e7d498e0a..614b5b272d9c6 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -40,6 +40,8 @@ static struct tau_temp
 	unsigned char grew;
 } tau[NR_CPUS];
 
+static bool tau_int_enable;
+
 #undef DEBUG
 
 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
@@ -54,22 +56,13 @@ static struct tau_temp
 
 static void set_thresholds(unsigned long cpu)
 {
-#ifdef CONFIG_TAU_INT
-	/*
-	 * setup THRM1,
-	 * threshold, valid bit, enable interrupts, interrupt when below threshold
-	 */
-	mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
+	u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0;
 
-	/* setup THRM2,
-	 * threshold, valid bit, enable interrupts, interrupt when above threshold
-	 */
-	mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
-#else
-	/* same thing but don't enable interrupts */
-	mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
-	mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
-#endif
+	/* setup THRM1, threshold, valid bit, interrupt when below threshold */
+	mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID);
+
+	/* setup THRM2, threshold, valid bit, interrupt when above threshold */
+	mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie);
 }
 
 static void TAUupdate(int cpu)
@@ -142,9 +135,8 @@ static void tau_timeout(void * info)
 	local_irq_save(flags);
 	cpu = smp_processor_id();
 
-#ifndef CONFIG_TAU_INT
-	TAUupdate(cpu);
-#endif
+	if (!tau_int_enable)
+		TAUupdate(cpu);
 
 	size = tau[cpu].high - tau[cpu].low;
 	if (size > min_window && ! tau[cpu].grew) {
@@ -225,6 +217,9 @@ static int __init TAU_init(void)
 		return 1;
 	}
 
+	tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
+			 !strcmp(cur_cpu_spec->platform, "ppc750");
+
 	tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
 	if (!tau_workq)
 		return -ENOMEM;
@@ -234,7 +229,7 @@ static int __init TAU_init(void)
 	queue_work(tau_workq, &tau_work);
 
 	pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
-		IS_ENABLED(CONFIG_TAU_INT) ? "interrupts" : "workqueue", shrink_timer);
+		tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
 	tau_initialized = 1;
 
 	return 0;
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index fb7515b4fa9c6..9fe36f0b54c1a 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -223,9 +223,8 @@ config TAU
 	  temperature within 2-4 degrees Celsius. This option shows the current
 	  on-die temperature in /proc/cpuinfo if the cpu supports it.
 
-	  Unfortunately, on some chip revisions, this sensor is very inaccurate
-	  and in many cases, does not work at all, so don't assume the cpu
-	  temp is actually what /proc/cpuinfo says it is.
+	  Unfortunately, this sensor is very inaccurate when uncalibrated, so
+	  don't assume the cpu temp is actually what /proc/cpuinfo says it is.
 
 config TAU_INT
 	bool "Interrupt driven TAU driver (DANGEROUS)"
-- 
2.26.2

[PATCH 5/5] powerpc/tau: Disable TAU between measurements

[Finn Thain]

Enabling CONFIG_TAU_INT causes random crashes:

Unrecoverable exception 1700 at c0009414 (msr=1000)
Oops: Unrecoverable exception, sig: 6 [#1]
BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 PowerMac
Modules linked in:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.7.0-pmac-00043-gd5f545e1a8593 #5
NIP:  c0009414 LR: c0009414 CTR: c00116fc
REGS: c0799eb8 TRAP: 1700   Not tainted  (5.7.0-pmac-00043-gd5f545e1a8593)
MSR:  00001000 <ME>  CR: 22000228  XER: 00000100

GPR00: 00000000 c0799f70 c076e300 00800000 0291c0ac 00e00000 c076e300 00049032
GPR08: 00000001 c00116fc 00000000 dfbd3200 ffffffff 007f80a8 00000000 00000000
GPR16: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 c075ce04
GPR24: c075ce04 dfff8880 c07b0000 c075ce04 00080000 00000001 c079ef98 c079ef5c
NIP [c0009414] arch_cpu_idle+0x24/0x6c
LR [c0009414] arch_cpu_idle+0x24/0x6c
Call Trace:
[c0799f70] [00000001] 0x1 (unreliable)
[c0799f80] [c0060990] do_idle+0xd8/0x17c
[c0799fa0] [c0060ba4] cpu_startup_entry+0x20/0x28
[c0799fb0] [c072d220] start_kernel+0x434/0x44c
[c0799ff0] [00003860] 0x3860
Instruction dump:
XXXXXXXX XXXXXXXX XXXXXXXX 3d20c07b XXXXXXXX XXXXXXXX XXXXXXXX 7c0802a6
XXXXXXXX XXXXXXXX XXXXXXXX 4e800421 XXXXXXXX XXXXXXXX XXXXXXXX 7d2000a6
---[ end trace 3a0c9b5cb216db6b ]---

Resolve this problem by disabling each THRMn comparator when handling
the associated THRMn interrupt and by disabling the TAU entirely when
updating THRMn thresholds.

Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 arch/powerpc/kernel/tau_6xx.c  | 65 +++++++++++++---------------------
 arch/powerpc/platforms/Kconfig |  9 ++---
 2 files changed, 26 insertions(+), 48 deletions(-)

diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
index 614b5b272d9c6..0b4694b8d2482 100644
--- a/arch/powerpc/kernel/tau_6xx.c
+++ b/arch/powerpc/kernel/tau_6xx.c
@@ -42,8 +42,6 @@ static struct tau_temp
 
 static bool tau_int_enable;
 
-#undef DEBUG
-
 /* TODO: put these in a /proc interface, with some sanity checks, and maybe
  * dynamic adjustment to minimize # of interrupts */
 /* configurable values for step size and how much to expand the window when
@@ -67,42 +65,33 @@ static void set_thresholds(unsigned long cpu)
 
 static void TAUupdate(int cpu)
 {
-	unsigned thrm;
-
-#ifdef DEBUG
-	printk("TAUupdate ");
-#endif
+	u32 thrm;
+	u32 bits = THRM1_TIV | THRM1_TIN | THRM1_V;
 
 	/* if both thresholds are crossed, the step_sizes cancel out
 	 * and the window winds up getting expanded twice. */
-	if((thrm = mfspr(SPRN_THRM1)) & THRM1_TIV){ /* is valid? */
-		if(thrm & THRM1_TIN){ /* crossed low threshold */
-			if (tau[cpu].low >= step_size){
-				tau[cpu].low -= step_size;
-				tau[cpu].high -= (step_size - window_expand);
-			}
-			tau[cpu].grew = 1;
-#ifdef DEBUG
-			printk("low threshold crossed ");
-#endif
+	thrm = mfspr(SPRN_THRM1);
+	if ((thrm & bits) == bits) {
+		mtspr(SPRN_THRM1, 0);
+
+		if (tau[cpu].low >= step_size) {
+			tau[cpu].low -= step_size;
+			tau[cpu].high -= (step_size - window_expand);
 		}
+		tau[cpu].grew = 1;
+		pr_debug("%s: low threshold crossed\n", __func__);
 	}
-	if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */
-		if(thrm & THRM1_TIN){ /* crossed high threshold */
-			if (tau[cpu].high <= 127-step_size){
-				tau[cpu].low += (step_size - window_expand);
-				tau[cpu].high += step_size;
-			}
-			tau[cpu].grew = 1;
-#ifdef DEBUG
-			printk("high threshold crossed ");
-#endif
+	thrm = mfspr(SPRN_THRM2);
+	if ((thrm & bits) == bits) {
+		mtspr(SPRN_THRM2, 0);
+
+		if (tau[cpu].high <= 127 - step_size) {
+			tau[cpu].low += (step_size - window_expand);
+			tau[cpu].high += step_size;
 		}
+		tau[cpu].grew = 1;
+		pr_debug("%s: high threshold crossed\n", __func__);
 	}
-
-#ifdef DEBUG
-	printk("grew = %d\n", tau[cpu].grew);
-#endif
 }
 
 #ifdef CONFIG_TAU_INT
@@ -127,17 +116,17 @@ void TAUException(struct pt_regs * regs)
 static void tau_timeout(void * info)
 {
 	int cpu;
-	unsigned long flags;
 	int size;
 	int shrink;
 
-	/* disabling interrupts *should* be okay */
-	local_irq_save(flags);
 	cpu = smp_processor_id();
 
 	if (!tau_int_enable)
 		TAUupdate(cpu);
 
+	/* Stop thermal sensor comparisons and interrupts */
+	mtspr(SPRN_THRM3, 0);
+
 	size = tau[cpu].high - tau[cpu].low;
 	if (size > min_window && ! tau[cpu].grew) {
 		/* do an exponential shrink of half the amount currently over size */
@@ -159,18 +148,12 @@ static void tau_timeout(void * info)
 
 	set_thresholds(cpu);
 
-	/*
-	 * Do the enable every time, since otherwise a bunch of (relatively)
-	 * complex sleep code needs to be added. One mtspr every time
-	 * tau_timeout is called is probably not a big deal.
-	 *
+	/* Restart thermal sensor comparisons and interrupts.
 	 * The "PowerPC 740 and PowerPC 750 Microprocessor Datasheet"
 	 * recommends that "the maximum value be set in THRM3 under all
 	 * conditions."
 	 */
 	mtspr(SPRN_THRM3, THRM3_SITV(0x1fff) | THRM3_E);
-
-	local_irq_restore(flags);
 }
 
 static struct workqueue_struct *tau_workq;
diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 9fe36f0b54c1a..b439b027a42f1 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -227,7 +227,7 @@ config TAU
 	  don't assume the cpu temp is actually what /proc/cpuinfo says it is.
 
 config TAU_INT
-	bool "Interrupt driven TAU driver (DANGEROUS)"
+	bool "Interrupt driven TAU driver (EXPERIMENTAL)"
 	depends on TAU
 	help
 	  The TAU supports an interrupt driven mode which causes an interrupt
@@ -235,12 +235,7 @@ config TAU_INT
 	  to get notified the temp has exceeded a range. With this option off,
 	  a timer is used to re-check the temperature periodically.
 
-	  However, on some cpus it appears that the TAU interrupt hardware
-	  is buggy and can cause a situation which would lead unexplained hard
-	  lockups.
-
-	  Unless you are extending the TAU driver, or enjoy kernel/hardware
-	  debugging, leave this option off.
+	  If in doubt, say N here.
 
 config TAU_AVERAGE
 	bool "Average high and low temp"
-- 
2.26.2

Re: [PATCH 0/5] powerpc/tau: TAU driver fixes

[Michael Ellerman]

On Sat, 05 Sep 2020 09:02:20 +1000, Finn Thain wrote:
> This patch series fixes various bugs in the Thermal Assist Unit driver.
> It was tested on 266 MHz and 292 MHz PowerBook G3 laptops.
> 
> 
> Finn Thain (5):
>   powerpc/tau: Use appropriate temperature sample interval
>   powerpc/tau: Convert from timer to workqueue
>   powerpc/tau: Remove duplicated set_thresholds() call
>   powerpc/tau: Check processor type before enabling TAU interrupt
>   powerpc/tau: Disable TAU between measurements
> 
> [...]

Applied to powerpc/next.

[1/5] powerpc/tau: Use appropriate temperature sample interval
      https://git.kernel.org/powerpc/c/66943005cc41f48e4d05614e8f76c0ca1812f0fd
[2/5] powerpc/tau: Convert from timer to workqueue
      https://git.kernel.org/powerpc/c/b1c6a0a10bfaf36ec82fde6f621da72407fa60a1
[3/5] powerpc/tau: Remove duplicated set_thresholds() call
      https://git.kernel.org/powerpc/c/420ab2bc7544d978a5d0762ee736412fe9c796ab
[4/5] powerpc/tau: Check processor type before enabling TAU interrupt
      https://git.kernel.org/powerpc/c/5e3119e15fed5b9a9a7e528665ff098a4a8dbdbc
[5/5] powerpc/tau: Disable TAU between measurements
      https://git.kernel.org/powerpc/c/e63d6fb5637e92725cf143559672a34b706bca4f

cheers