[MIPS] Sibyte: Fix race in sb1250_gettimeoffset().
From Dave Johnson <djohnson+linuxmips@sw.starentnetworks.com>:
sb1250_gettimeoffset() simply reads the current cpu 0 timer remaining
value, however once this counter reaches 0 and the interrupt is raised,
it immediately resets and begins to count down again.
If sb1250_gettimeoffset() is called on cpu 1 via do_gettimeofday() after
the timer has reset but prior to cpu 0 processing the interrupt and
taking write_seqlock() in timer_interrupt() it will return a full value
(or close to it) causing time to jump backwards 1ms. Once cpu 0 handles
the interrupt and timer_interrupt() gets far enough along it will jump
forward 1ms.
Fix this problem by implementing mips_hpt_*() on sb1250 using a spare
timer unrelated to the existing periodic interrupt timers. It runs at
1Mhz with a full 23bit counter. This eliminated the custom
do_gettimeoffset() for sb1250 and allowed use of the generic
fixed_rate_gettimeoffset() using mips_hpt_*() and timerhi/timerlo.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/sibyte/sb1250/time.c b/arch/mips/sibyte/sb1250/time.c
index adc0b52..1588f6d 100644
--- a/arch/mips/sibyte/sb1250/time.c
+++ b/arch/mips/sibyte/sb1250/time.c
@@ -47,23 +47,51 @@
#define IMR_IP3_VAL K_INT_MAP_I1
#define IMR_IP4_VAL K_INT_MAP_I2
+#define SB1250_HPT_NUM 3
+#define SB1250_HPT_VALUE M_SCD_TIMER_CNT /* max value */
+#define SB1250_HPT_SHIFT ((sizeof(unsigned int)*8)-V_SCD_TIMER_WIDTH)
+
+
extern int sb1250_steal_irq(int irq);
+static unsigned int sb1250_hpt_read(void);
+static void sb1250_hpt_init(unsigned int);
+
+static unsigned int hpt_offset;
+
+void __init sb1250_hpt_setup(void)
+{
+ int cpu = smp_processor_id();
+
+ if (!cpu) {
+ /* Setup hpt using timer #3 but do not enable irq for it */
+ __raw_writeq(0, IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CFG)));
+ __raw_writeq(SB1250_HPT_VALUE,
+ IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_INIT)));
+ __raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS,
+ IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CFG)));
+
+ /*
+ * we need to fill 32 bits, so just use the upper 23 bits and pretend
+ * the timer is going 512Mhz instead of 1Mhz
+ */
+ mips_hpt_frequency = V_SCD_TIMER_FREQ << SB1250_HPT_SHIFT;
+ mips_hpt_init = sb1250_hpt_init;
+ mips_hpt_read = sb1250_hpt_read;
+ }
+}
+
+
void sb1250_time_init(void)
{
int cpu = smp_processor_id();
int irq = K_INT_TIMER_0+cpu;
- /* Only have 4 general purpose timers */
- if (cpu > 3) {
+ /* Only have 4 general purpose timers, and we use last one as hpt */
+ if (cpu > 2) {
BUG();
}
- if (!cpu) {
- /* Use our own gettimeoffset() routine */
- do_gettimeoffset = sb1250_gettimeoffset;
- }
-
sb1250_mask_irq(cpu, irq);
/* Map the timer interrupt to ip[4] of this cpu */
@@ -103,7 +131,7 @@
int cpu = smp_processor_id();
int irq = K_INT_TIMER_0 + cpu;
- /* Reset the timer */
+ /* ACK interrupt */
____raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS,
IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG)));
@@ -122,15 +150,26 @@
}
/*
- * We use our own do_gettimeoffset() instead of the generic one,
- * because the generic one does not work for SMP case.
- * In addition, since we use general timer 0 for system time,
- * we can get accurate intra-jiffy offset without calibration.
+ * The HPT is free running from SB1250_HPT_VALUE down to 0 then starts over
+ * again. There's no easy way to set to a specific value so store init value
+ * in hpt_offset and subtract each time.
+ *
+ * Note: Timer isn't full 32bits so shift it into the upper part making
+ * it appear to run at a higher frequency.
*/
-unsigned long sb1250_gettimeoffset(void)
+static unsigned int sb1250_hpt_read(void)
{
- unsigned long count =
- __raw_readq(IOADDR(A_SCD_TIMER_REGISTER(0, R_SCD_TIMER_CNT)));
+ unsigned int count;
- return 1000000/HZ - count;
- }
+ count = G_SCD_TIMER_CNT(__raw_readq(IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CNT))));
+
+ count = (SB1250_HPT_VALUE - count) << SB1250_HPT_SHIFT;
+
+ return count - hpt_offset;
+}
+
+static void sb1250_hpt_init(unsigned int count)
+{
+ hpt_offset = count;
+ return;
+}
diff --git a/arch/mips/sibyte/swarm/setup.c b/arch/mips/sibyte/swarm/setup.c
index b614ca0..b661d24 100644
--- a/arch/mips/sibyte/swarm/setup.c
+++ b/arch/mips/sibyte/swarm/setup.c
@@ -70,6 +70,12 @@
return "SiByte " SIBYTE_BOARD_NAME;
}
+void __init swarm_time_init(void)
+{
+ /* Setup HPT */
+ sb1250_hpt_setup();
+}
+
void __init swarm_timer_setup(struct irqaction *irq)
{
/*
@@ -109,6 +115,7 @@
panic_timeout = 5; /* For debug. */
+ board_time_init = swarm_time_init;
board_timer_setup = swarm_timer_setup;
board_be_handler = swarm_be_handler;
diff --git a/include/asm-mips/sibyte/sb1250.h b/include/asm-mips/sibyte/sb1250.h
index a474c29..b09e16c 100644
--- a/include/asm-mips/sibyte/sb1250.h
+++ b/include/asm-mips/sibyte/sb1250.h
@@ -45,8 +45,8 @@
extern unsigned int periph_rev;
extern unsigned int zbbus_mhz;
+extern void sb1250_hpt_setup(void);
extern void sb1250_time_init(void);
-extern unsigned long sb1250_gettimeoffset(void);
extern void sb1250_mask_irq(int cpu, int irq);
extern void sb1250_unmask_irq(int cpu, int irq);
extern void sb1250_smp_finish(void);