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m68k: mvme16x: Handle timer counter overflow

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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>
This commit is contained in:
Finn Thain 2018-12-01 11:53:10 +11:00 committed by Geert Uytterhoeven
parent 3d744eee38
commit 19999a8b87
1 changed files with 32 additions and 13 deletions
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45
arch/m68k/mvme16x/config.c
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@ -115,11 +115,11 @@ static void __init mvme16x_init_IRQ (void)
m68k_setup_user_interrupt(VEC_USER, 192); m68k_setup_user_interrupt(VEC_USER, 192);
} }
#define pcc2chip ((volatile u_char *)0xfff42000) #define PCC2CHIP (0xfff42000)
#define PccSCCMICR 0x1d #define PCCSCCMICR (PCC2CHIP + 0x1d)
#define PccSCCTICR 0x1e #define PCCSCCTICR (PCC2CHIP + 0x1e)
#define PccSCCRICR 0x1f #define PCCSCCRICR (PCC2CHIP + 0x1f)
#define PccTPIACKR 0x25 #define PCCTPIACKR (PCC2CHIP + 0x25)
#ifdef CONFIG_EARLY_PRINTK #ifdef CONFIG_EARLY_PRINTK
@ -227,10 +227,10 @@ void mvme16x_cons_write(struct console *co, const char *str, unsigned count)
base_addr[CyIER] = CyTxMpty; base_addr[CyIER] = CyTxMpty;
while (1) { while (1) {
if (pcc2chip[PccSCCTICR] & 0x20) if (in_8(PCCSCCTICR) & 0x20)
{ {
/* We have a Tx int. Acknowledge it */ /* We have a Tx int. Acknowledge it */
sink = pcc2chip[PccTPIACKR]; sink = in_8(PCCTPIACKR);
if ((base_addr[CyLICR] >> 2) == port) { if ((base_addr[CyLICR] >> 2) == port) {
if (i == count) { if (i == count) {
/* Last char of string is now output */ /* Last char of string is now output */
@ -359,13 +359,26 @@ static u32 clk_total;
#define PCC_TIMER_CLOCK_FREQ 1000000 #define PCC_TIMER_CLOCK_FREQ 1000000
#define PCC_TIMER_CYCLES (PCC_TIMER_CLOCK_FREQ / HZ) #define PCC_TIMER_CYCLES (PCC_TIMER_CLOCK_FREQ / HZ)
#define PCCTCMP1 (PCC2CHIP + 0x04)
#define PCCTCNT1 (PCC2CHIP + 0x08)
#define PCCTOVR1 (PCC2CHIP + 0x17)
#define PCCTIC1 (PCC2CHIP + 0x1b)
#define PCCTOVR1_TIC_EN 0x01
#define PCCTOVR1_COC_EN 0x02
#define PCCTOVR1_OVR_CLR 0x04
#define PCCTIC1_INT_CLR 0x08
#define PCCTIC1_INT_EN 0x10
static irqreturn_t mvme16x_timer_int (int irq, void *dev_id) static irqreturn_t mvme16x_timer_int (int irq, void *dev_id)
{ {
irq_handler_t timer_routine = dev_id; irq_handler_t timer_routine = dev_id;
unsigned long flags; unsigned long flags;
local_irq_save(flags); local_irq_save(flags);
*(volatile unsigned char *)0xfff4201b |= 8; out_8(PCCTIC1, in_8(PCCTIC1) | PCCTIC1_INT_CLR);
out_8(PCCTOVR1, PCCTOVR1_OVR_CLR);
clk_total += PCC_TIMER_CYCLES; clk_total += PCC_TIMER_CYCLES;
timer_routine(0, NULL); timer_routine(0, NULL);
local_irq_restore(flags); local_irq_restore(flags);
@ -379,10 +392,10 @@ void mvme16x_sched_init (irq_handler_t timer_routine)
int irq; int irq;
/* Using PCCchip2 or MC2 chip tick timer 1 */ /* Using PCCchip2 or MC2 chip tick timer 1 */
*(volatile unsigned long *)0xfff42008 = 0; out_be32(PCCTCNT1, 0);
*(volatile unsigned long *)0xfff42004 = PCC_TIMER_CYCLES; out_be32(PCCTCMP1, PCC_TIMER_CYCLES);
*(volatile unsigned char *)0xfff42017 |= 3; out_8(PCCTOVR1, in_8(PCCTOVR1) | PCCTOVR1_TIC_EN | PCCTOVR1_COC_EN);
*(volatile unsigned char *)0xfff4201b = 0x16; out_8(PCCTIC1, PCCTIC1_INT_EN | 6);
if (request_irq(MVME16x_IRQ_TIMER, mvme16x_timer_int, IRQF_TIMER, "timer", if (request_irq(MVME16x_IRQ_TIMER, mvme16x_timer_int, IRQF_TIMER, "timer",
timer_routine)) timer_routine))
panic ("Couldn't register timer int"); panic ("Couldn't register timer int");
@ -401,10 +414,16 @@ void mvme16x_sched_init (irq_handler_t timer_routine)
static u64 mvme16x_read_clk(struct clocksource *cs) static u64 mvme16x_read_clk(struct clocksource *cs)
{ {
unsigned long flags; unsigned long flags;
u8 overflow, tmp;
u32 ticks; u32 ticks;
local_irq_save(flags); local_irq_save(flags);
ticks = *(volatile u32 *)0xfff42008; tmp = in_8(PCCTOVR1) >> 4;
ticks = in_be32(PCCTCNT1);
overflow = in_8(PCCTOVR1) >> 4;
if (overflow != tmp)
ticks = in_be32(PCCTCNT1);
ticks += overflow * PCC_TIMER_CYCLES;
ticks += clk_total; ticks += clk_total;
local_irq_restore(flags); local_irq_restore(flags);