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Commit 384859d2 authored by Andreas Larsson's avatar Andreas Larsson Committed by David S. Miller
Browse files

sparc: leon: Fix race condition between leon_cycles_offset and timer_interrupt 



This makes sure that leon_cycles_offset takes the pending bit into
account and that leon_clear_clock_irq clears the pending bit. Otherwise,
if leon_cycles_offset is executed after the timer has wrapped but before
timer_interrupt has increased timer_cs_internal_counter, time can be
perceived to go backwards.

Signed-off-by: default avatarAndreas Larsson <andreas@gaisler.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 74cad25c

arch/sparc/kernel/leon_kernel.c

+28 −3
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ unsigned long amba_system_id; 
static DEFINE_SPINLOCK(leon_irq_lock);



static unsigned long leon3_gptimer_idx; /* Timer Index (0..6) within Timer Core */

static unsigned long leon3_gptimer_ackmask; /* For clearing pending bit */

unsigned long leon3_gptimer_irq; /* interrupt controller irq number */

unsigned int sparc_leon_eirq;

#define LEON_IMASK(cpu) (&leon3_irqctrl_regs->mask[cpu])
@@ -260,11 +261,19 @@ void leon_update_virq_handling(unsigned int virq, 


static u32 leon_cycles_offset(void)

{

	u32 rld, val, off;

	u32 rld, val, ctrl, off;



	rld = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].rld);

	val = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].val);

	ctrl = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl);

	if (LEON3_GPTIMER_CTRL_ISPENDING(ctrl)) {

		val = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].val);

		off = 2 * rld - val;

	} else {

		off = rld - val;

	return rld - val;

	}



	return off;

}



#ifdef CONFIG_SMP
@@ -302,6 +311,7 @@ void __init leon_init_timers(void) 
	int ampopts;

	int err;

	u32 config;

	u32 ctrl;



	sparc_config.get_cycles_offset = leon_cycles_offset;

	sparc_config.cs_period = 1000000 / HZ;
@@ -374,6 +384,16 @@ void __init leon_init_timers(void) 
	if (!(leon3_gptimer_regs && leon3_irqctrl_regs && leon3_gptimer_irq))

		goto bad;



	ctrl = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl);

	LEON3_BYPASS_STORE_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl,

			      ctrl | LEON3_GPTIMER_CTRL_PENDING);

	ctrl = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl);



	if ((ctrl & LEON3_GPTIMER_CTRL_PENDING) != 0)

		leon3_gptimer_ackmask = ~LEON3_GPTIMER_CTRL_PENDING;

	else

		leon3_gptimer_ackmask = ~0;



	LEON3_BYPASS_STORE_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].val, 0);

	LEON3_BYPASS_STORE_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].rld,

				(((1000000 / HZ) - 1)));
@@ -452,6 +472,11 @@ void __init leon_init_timers(void) 


static void leon_clear_clock_irq(void)

{

	u32 ctrl;



	ctrl = LEON3_BYPASS_LOAD_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl);

	LEON3_BYPASS_STORE_PA(&leon3_gptimer_regs->e[leon3_gptimer_idx].ctrl,

			      ctrl & leon3_gptimer_ackmask);

}



static void leon_load_profile_irq(int cpu, unsigned int limit)