Commit e63d6fb5 authored by Finn Thain's avatar Finn Thain Committed by Michael Ellerman
Browse files

powerpc/tau: Disable TAU between measurements 



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: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: default avatarFinn Thain <fthain@telegraphics.com.au>
Tested-by: default avatarStan Johnson <userm57@yahoo.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5a0ba3dc5612c7aac596727331284a3676c08472.1599260540.git.fthain@telegraphics.com.au
parent 5e3119e1

arch/powerpc/kernel/tau_6xx.c

+24 −41
Original line number Diff line number Diff line
@@ -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
@@ -67,44 +65,35 @@ 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 */

	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;

#ifdef DEBUG

			printk("low threshold crossed ");

#endif

		}

		pr_debug("%s: low threshold crossed\n", __func__);

	}

	if((thrm = mfspr(SPRN_THRM2)) & THRM1_TIV){ /* is valid? */

		if(thrm & THRM1_TIN){ /* crossed high threshold */

	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;

#ifdef DEBUG

			printk("high threshold crossed ");

#endif

		pr_debug("%s: high threshold crossed\n", __func__);

	}

}



#ifdef DEBUG

	printk("grew = %d\n", tau[cpu].grew);

#endif

}



#ifdef CONFIG_TAU_INT

/*

 * TAU interrupts - called when we have a thermal assist unit interrupt
@@ -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;

arch/powerpc/platforms/Kconfig

+2 −7
Original line number Diff line number Diff line
@@ -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"

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