diff options
Diffstat (limited to 'packages/linux/linux-omap2-git/beagleboard/02-gptimer_clear_tocr')
| -rw-r--r-- | packages/linux/linux-omap2-git/beagleboard/02-gptimer_clear_tocr | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/packages/linux/linux-omap2-git/beagleboard/02-gptimer_clear_tocr b/packages/linux/linux-omap2-git/beagleboard/02-gptimer_clear_tocr new file mode 100644 index 0000000000..b92c5dd126 --- /dev/null +++ b/packages/linux/linux-omap2-git/beagleboard/02-gptimer_clear_tocr @@ -0,0 +1,97 @@ +OMAP2/3 GPTIMER: clear TOCR register after timer overflow interrupt and during load + +From: Paul Walmsley <paul@pwsan.com> + +There appears to be a hardware bug in the 1-ms tick generation section +of the GPTIMER blocks on some OMAP3530 chips. TOCR is sometimes +incremented when a a timer overflow event occurs and TPIR = TPNR = +TOWR = TOCR = 0, in contradiction of 34xx TRM 16.2.4.2.1. When TOCR +is incremented under these conditions, the timer will not generate any +further overflow interrupts. (The kernel currently relies on overflow +interrupts to generate ticks and drive the scheduler.) + +This patch works around the bug by clearing TOCR in the GPTIMER +overflow ISR and in the timer load functions. + +The precise sequence of hardware events needed to reproduce this bug +is still unknown. Without this patch, the bug is consistently +observable on several BeagleBoards (including mine and Koen's) within +a few minutes of boot. It's not clear whether this bug is present on +all OMAP3 revisions, or whether it is simply specific to certain +OMAP3530ES2.2 lots. + +This patch fixes the "serial hangs" reported by some BeagleBoard +users. During these hangs, characters are still received from the +serial port, so magic SysRq will still work; but characters are never +delivered on to the underlying line discipline. This since +tty_flip_buffer_push() uses schedule_delayed_work() to defer passing +the input buffer to the line discipline, but the delayed work function +is never called since no timer tick ever arrives. + +The patch should also fix some other sporadic boot hangs reported by +BeagleBoard users that are due to timer interrupt non-delivery. +--- + + arch/arm/mach-omap2/timer-gp.c | 1 + + arch/arm/plat-omap/dmtimer.c | 8 ++++++++ + include/asm-arm/arch-omap/dmtimer.h | 2 ++ + 3 files changed, 11 insertions(+), 0 deletions(-) + +diff --git a/arch/arm/mach-omap2/timer-gp.c b/arch/arm/mach-omap2/timer-gp.c +index edc0c9e..869fe14 100644 +--- a/arch/arm/mach-omap2/timer-gp.c ++++ b/arch/arm/mach-omap2/timer-gp.c +@@ -44,6 +44,7 @@ static irqreturn_t omap2_gp_timer_interrupt(int irq, void *dev_id) + struct omap_dm_timer *gpt = (struct omap_dm_timer *)dev_id; + struct clock_event_device *evt = &clockevent_gpt; + ++ omap_dm_timer_clear_ovf_cnt(gpt); + omap_dm_timer_write_status(gpt, OMAP_TIMER_INT_OVERFLOW); + + evt->event_handler(evt); +diff --git a/arch/arm/plat-omap/dmtimer.c b/arch/arm/plat-omap/dmtimer.c +index f22506a..2cbb4cc 100644 +--- a/arch/arm/plat-omap/dmtimer.c ++++ b/arch/arm/plat-omap/dmtimer.c +@@ -543,6 +543,8 @@ void omap_dm_timer_set_load(struct omap_dm_timer *timer, int autoreload, + while (readl(timer->io_base + (OMAP_TIMER_WRITE_PEND_REG & 0xff))) + cpu_relax(); + ++ omap_dm_timer_write_reg(timer, OMAP_TIMER_TICK_INT_MASK_SET_REG, 0); ++ + omap_dm_timer_write_reg(timer, OMAP_TIMER_TRIGGER_REG, 0); + } + +@@ -561,6 +563,7 @@ void omap_dm_timer_set_load_start(struct omap_dm_timer *timer, int autoreload, + + omap_dm_timer_write_reg(timer, OMAP_TIMER_COUNTER_REG, load); + omap_dm_timer_write_reg(timer, OMAP_TIMER_LOAD_REG, load); ++ omap_dm_timer_write_reg(timer, OMAP_TIMER_TICK_INT_MASK_SET_REG, 0); + omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l); + } + +@@ -614,6 +617,11 @@ void omap_dm_timer_set_int_enable(struct omap_dm_timer *timer, + omap_dm_timer_write_reg(timer, OMAP_TIMER_WAKEUP_EN_REG, value); + } + ++void omap_dm_timer_clear_ovf_cnt(struct omap_dm_timer *timer) ++{ ++ omap_dm_timer_write_reg(timer, OMAP_TIMER_TICK_INT_MASK_SET_REG, 0); ++} ++ + unsigned int omap_dm_timer_read_status(struct omap_dm_timer *timer) + { + unsigned int l; +diff --git a/include/asm-arm/arch-omap/dmtimer.h b/include/asm-arm/arch-omap/dmtimer.h +index 02b29e8..7b1138b 100644 +--- a/include/asm-arm/arch-omap/dmtimer.h ++++ b/include/asm-arm/arch-omap/dmtimer.h +@@ -73,6 +73,8 @@ void omap_dm_timer_set_prescaler(struct omap_dm_timer *timer, int prescaler); + + void omap_dm_timer_set_int_enable(struct omap_dm_timer *timer, unsigned int value); + ++void omap_dm_timer_clear_ovf_cnt(struct omap_dm_timer *timer); ++ + unsigned int omap_dm_timer_read_status(struct omap_dm_timer *timer); + void omap_dm_timer_write_status(struct omap_dm_timer *timer, unsigned int value); + unsigned int omap_dm_timer_read_counter(struct omap_dm_timer *timer); |