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clocksource/drivers/timer-ti-dm: Fix posted mode status check order 

When the timer is configured in posted mode, we need to check the write-
posted status register (TWPS) before writing to the register.

We now check TWPS after the write starting with commit 52762fbd1c
("clocksource/drivers/timer-ti-dm: Add clockevent and clocksource
support").

For example, in the TRM for am571x the following is documented in chapter
"22.2.4.13.1.1 Write Posting Synchronization Mode":

"For each register, a status bit is provided in the timer write-posted
 status (TWPS) register. In this mode, it is mandatory that software check
 this status bit before any write access. If a write is attempted to a
 register with a previous access pending, the previous access is discarded
 without notice."

The regression happened when I updated the code to use standard read/write
accessors for the driver instead of using __omap_dm_timer_load_start().
We have__omap_dm_timer_load_start() check the TWPS status correctly using
__omap_dm_timer_write().

Fixes: 52762fbd1c ("clocksource/drivers/timer-ti-dm: Add clockevent and clocksource support")
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210304072135.52712-2-tony@atomide.com
This commit is contained in:
Tony Lindgren 2021-03-04 09:21:33 +02:00 committed by Daniel Lezcano
parent 446e1a9435
commit 212709926c
1 changed files with 6 additions and 6 deletions
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12
drivers/clocksource/timer-ti-dm-systimer.c
View File

@ -449,13 +449,13 @@ static int dmtimer_set_next_event(unsigned long cycles,
struct dmtimer_systimer *t = &clkevt->t;
void __iomem *pend = t->base + t->pend;
writel_relaxed(0xffffffff - cycles, t->base + t->counter);
while (readl_relaxed(pend) & WP_TCRR)
cpu_relax();
writel_relaxed(0xffffffff - cycles, t->base + t->counter);
writel_relaxed(OMAP_TIMER_CTRL_ST, t->base + t->ctrl);
while (readl_relaxed(pend) & WP_TCLR)
cpu_relax();
writel_relaxed(OMAP_TIMER_CTRL_ST, t->base + t->ctrl);
return 0;
}
@ -490,18 +490,18 @@ static int dmtimer_set_periodic(struct clock_event_device *evt)
dmtimer_clockevent_shutdown(evt);
/* Looks like we need to first set the load value separately */
writel_relaxed(clkevt->period, t->base + t->load);
while (readl_relaxed(pend) & WP_TLDR)
cpu_relax();
writel_relaxed(clkevt->period, t->base + t->load);
writel_relaxed(clkevt->period, t->base + t->counter);
while (readl_relaxed(pend) & WP_TCRR)
cpu_relax();
writel_relaxed(clkevt->period, t->base + t->counter);
writel_relaxed(OMAP_TIMER_CTRL_AR | OMAP_TIMER_CTRL_ST,
t->base + t->ctrl);
while (readl_relaxed(pend) & WP_TCLR)
cpu_relax();
writel_relaxed(OMAP_TIMER_CTRL_AR | OMAP_TIMER_CTRL_ST,
t->base + t->ctrl);
return 0;
}