diff options
| author |   Finn Thain <fthain@telegraphics.com.au> | 2018-12-01 11:53:10 +1100 |
|---|---|---|
| committer |   Geert Uytterhoeven <geert@linux-m68k.org> | 2019-03-25 10:22:24 +0100 |
| commit | 7529b90d051e4629884771ba2b1d3a87d2c6a9d7 (patch) | |
| tree | f95960fd233bf19c0840e65a9281d71576a2abdc /arch/m68k | |
| parent | m68k: mvme147: Convert to clocksource API (diff) | |
| download | linux-dev-7529b90d051e4629884771ba2b1d3a87d2c6a9d7.tar.xz linux-dev-7529b90d051e4629884771ba2b1d3a87d2c6a9d7.zip | |
m68k: mvme147: Handle timer counter overflow
Reading the timer counter races with timer overflow (and the
corresponding interrupt). This is resolved by reading the overflow
register and taking this value into account. The interrupt handler
must clear the overflow register when it eventually executes.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Diffstat (limited to 'arch/m68k')
| -rw-r--r-- | arch/m68k/include/asm/mvme147hw.h | 1 | ||||
| -rw-r--r-- | arch/m68k/mvme147/config.c | 21 |
2 files changed, 12 insertions, 10 deletions
diff --git a/arch/m68k/include/asm/mvme147hw.h b/arch/m68k/include/asm/mvme147hw.h index 7c3dd513128e..257b29184af9 100644 --- a/arch/m68k/include/asm/mvme147hw.h +++ b/arch/m68k/include/asm/mvme147hw.h @@ -66,6 +66,7 @@ struct pcc_regs { #define PCC_INT_ENAB 0x08 #define PCC_TIMER_INT_CLR 0x80 +#define PCC_TIMER_CLR_OVF 0x04 #define PCC_LEVEL_ABORT 0x07 #define PCC_LEVEL_SERIAL 0x04 diff --git a/arch/m68k/mvme147/config.c b/arch/m68k/mvme147/config.c index c44a254e8a8c..545a1fe0e119 100644 --- a/arch/m68k/mvme147/config.c +++ b/arch/m68k/mvme147/config.c @@ -118,7 +118,7 @@ static irqreturn_t mvme147_timer_int (int irq, void *dev_id) local_irq_save(flags); m147_pcc->t1_int_cntrl = PCC_TIMER_INT_CLR; - m147_pcc->t1_int_cntrl = PCC_INT_ENAB|PCC_LEVEL_TIMER1; + m147_pcc->t1_cntrl = PCC_TIMER_CLR_OVF; clk_total += PCC_TIMER_CYCLES; timer_routine(0, NULL); local_irq_restore(flags); @@ -144,21 +144,22 @@ void mvme147_sched_init (irq_handler_t timer_routine) clocksource_register_hz(&mvme147_clk, PCC_TIMER_CLOCK_FREQ); } -/* XXX There are race hazards in this code XXX */ static u64 mvme147_read_clk(struct clocksource *cs) { unsigned long flags; - volatile unsigned short *cp = (volatile unsigned short *)0xfffe1012; - unsigned short n; + u8 overflow, tmp; + u16 count; u32 ticks; local_irq_save(flags); - n = *cp; - while (n != *cp) - n = *cp; - - n -= PCC_TIMER_PRELOAD; - ticks = clk_total + n; + tmp = m147_pcc->t1_cntrl >> 4; + count = m147_pcc->t1_count; + overflow = m147_pcc->t1_cntrl >> 4; + if (overflow != tmp) + count = m147_pcc->t1_count; + count -= PCC_TIMER_PRELOAD; + ticks = count + overflow * PCC_TIMER_CYCLES; + ticks += clk_total; local_irq_restore(flags); return ticks; |