diff options
author | Ralf Baechle <ralf@linux-mips.org> | 2006-03-14 19:03:29 -0500 |
---|---|---|
committer | Ralf Baechle <ralf@linux-mips.org> | 2006-03-18 11:59:30 -0500 |
commit | a904f7478561464f9fe74929b81fec237b6ff4c3 (patch) | |
tree | 6018ab25ea391aad0f4f33f0613e2b9fdbe36637 /arch/mips/sibyte/sb1250/time.c | |
parent | 4308cb16286c96d980570cc5319173b524220c06 (diff) |
[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>
Diffstat (limited to 'arch/mips/sibyte/sb1250/time.c')
-rw-r--r-- | arch/mips/sibyte/sb1250/time.c | 73 |
1 files changed, 56 insertions, 17 deletions
diff --git a/arch/mips/sibyte/sb1250/time.c b/arch/mips/sibyte/sb1250/time.c index adc0b5271a06..1588f6debd90 100644 --- a/arch/mips/sibyte/sb1250/time.c +++ b/arch/mips/sibyte/sb1250/time.c | |||
@@ -47,23 +47,51 @@ | |||
47 | #define IMR_IP3_VAL K_INT_MAP_I1 | 47 | #define IMR_IP3_VAL K_INT_MAP_I1 |
48 | #define IMR_IP4_VAL K_INT_MAP_I2 | 48 | #define IMR_IP4_VAL K_INT_MAP_I2 |
49 | 49 | ||
50 | #define SB1250_HPT_NUM 3 | ||
51 | #define SB1250_HPT_VALUE M_SCD_TIMER_CNT /* max value */ | ||
52 | #define SB1250_HPT_SHIFT ((sizeof(unsigned int)*8)-V_SCD_TIMER_WIDTH) | ||
53 | |||
54 | |||
50 | extern int sb1250_steal_irq(int irq); | 55 | extern int sb1250_steal_irq(int irq); |
51 | 56 | ||
57 | static unsigned int sb1250_hpt_read(void); | ||
58 | static void sb1250_hpt_init(unsigned int); | ||
59 | |||
60 | static unsigned int hpt_offset; | ||
61 | |||
62 | void __init sb1250_hpt_setup(void) | ||
63 | { | ||
64 | int cpu = smp_processor_id(); | ||
65 | |||
66 | if (!cpu) { | ||
67 | /* Setup hpt using timer #3 but do not enable irq for it */ | ||
68 | __raw_writeq(0, IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CFG))); | ||
69 | __raw_writeq(SB1250_HPT_VALUE, | ||
70 | IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_INIT))); | ||
71 | __raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS, | ||
72 | IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CFG))); | ||
73 | |||
74 | /* | ||
75 | * we need to fill 32 bits, so just use the upper 23 bits and pretend | ||
76 | * the timer is going 512Mhz instead of 1Mhz | ||
77 | */ | ||
78 | mips_hpt_frequency = V_SCD_TIMER_FREQ << SB1250_HPT_SHIFT; | ||
79 | mips_hpt_init = sb1250_hpt_init; | ||
80 | mips_hpt_read = sb1250_hpt_read; | ||
81 | } | ||
82 | } | ||
83 | |||
84 | |||
52 | void sb1250_time_init(void) | 85 | void sb1250_time_init(void) |
53 | { | 86 | { |
54 | int cpu = smp_processor_id(); | 87 | int cpu = smp_processor_id(); |
55 | int irq = K_INT_TIMER_0+cpu; | 88 | int irq = K_INT_TIMER_0+cpu; |
56 | 89 | ||
57 | /* Only have 4 general purpose timers */ | 90 | /* Only have 4 general purpose timers, and we use last one as hpt */ |
58 | if (cpu > 3) { | 91 | if (cpu > 2) { |
59 | BUG(); | 92 | BUG(); |
60 | } | 93 | } |
61 | 94 | ||
62 | if (!cpu) { | ||
63 | /* Use our own gettimeoffset() routine */ | ||
64 | do_gettimeoffset = sb1250_gettimeoffset; | ||
65 | } | ||
66 | |||
67 | sb1250_mask_irq(cpu, irq); | 95 | sb1250_mask_irq(cpu, irq); |
68 | 96 | ||
69 | /* Map the timer interrupt to ip[4] of this cpu */ | 97 | /* Map the timer interrupt to ip[4] of this cpu */ |
@@ -103,7 +131,7 @@ void sb1250_timer_interrupt(struct pt_regs *regs) | |||
103 | int cpu = smp_processor_id(); | 131 | int cpu = smp_processor_id(); |
104 | int irq = K_INT_TIMER_0 + cpu; | 132 | int irq = K_INT_TIMER_0 + cpu; |
105 | 133 | ||
106 | /* Reset the timer */ | 134 | /* ACK interrupt */ |
107 | ____raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS, | 135 | ____raw_writeq(M_SCD_TIMER_ENABLE | M_SCD_TIMER_MODE_CONTINUOUS, |
108 | IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG))); | 136 | IOADDR(A_SCD_TIMER_REGISTER(cpu, R_SCD_TIMER_CFG))); |
109 | 137 | ||
@@ -122,15 +150,26 @@ void sb1250_timer_interrupt(struct pt_regs *regs) | |||
122 | } | 150 | } |
123 | 151 | ||
124 | /* | 152 | /* |
125 | * We use our own do_gettimeoffset() instead of the generic one, | 153 | * The HPT is free running from SB1250_HPT_VALUE down to 0 then starts over |
126 | * because the generic one does not work for SMP case. | 154 | * again. There's no easy way to set to a specific value so store init value |
127 | * In addition, since we use general timer 0 for system time, | 155 | * in hpt_offset and subtract each time. |
128 | * we can get accurate intra-jiffy offset without calibration. | 156 | * |
157 | * Note: Timer isn't full 32bits so shift it into the upper part making | ||
158 | * it appear to run at a higher frequency. | ||
129 | */ | 159 | */ |
130 | unsigned long sb1250_gettimeoffset(void) | 160 | static unsigned int sb1250_hpt_read(void) |
131 | { | 161 | { |
132 | unsigned long count = | 162 | unsigned int count; |
133 | __raw_readq(IOADDR(A_SCD_TIMER_REGISTER(0, R_SCD_TIMER_CNT))); | ||
134 | 163 | ||
135 | return 1000000/HZ - count; | 164 | count = G_SCD_TIMER_CNT(__raw_readq(IOADDR(A_SCD_TIMER_REGISTER(SB1250_HPT_NUM, R_SCD_TIMER_CNT)))); |
136 | } | 165 | |
166 | count = (SB1250_HPT_VALUE - count) << SB1250_HPT_SHIFT; | ||
167 | |||
168 | return count - hpt_offset; | ||
169 | } | ||
170 | |||
171 | static void sb1250_hpt_init(unsigned int count) | ||
172 | { | ||
173 | hpt_offset = count; | ||
174 | return; | ||
175 | } | ||