From: Finn Thain <fthain@telegraphics.com.au>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
Philip Blundell <philb@gnu.org>
Cc: Andreas Schwab <schwab@linux-m68k.org>,
Arnd Bergmann <arnd@arndb.de>,
Stephen N Chivers <schivers@csc.com.au>,
Thomas Gleixner <tglx@linutronix.de>,
Kars de Jong <jongk@linux-m68k.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Michael Schmitz <schmitzmic@gmail.com>,
John Stultz <john.stultz@linaro.org>,
Linus Walleij <linus.walleij@linaro.org>,
linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org
Subject: [PATCH v4 09/14] m68k: hp300: Handle timer counter overflow
Date: Sat, 01 Dec 2018 11:53:10 +1100 [thread overview]
Message-ID: <2aa62fd1164340976feb6e5e58a3c960083a3d95.1543625590.git.fthain@telegraphics.com.au> (raw)
In-Reply-To: <cover.1543625590.git.fthain@telegraphics.com.au>
Because hp300_read_clk() never checks the timer interrupt flag it may
fail to notice that the timer has wrapped, allowing the clock to jump
backwards. This is not a new problem.
This is resolved by checking the interrupt flag and, if need be,
taking wrap-around into account. The interrupt handler clears the flag
when it eventually executes.
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
TODO: find a spare counter for the clocksource, rather than hanging
it off the HZ timer.
Changed since v3:
- Use clk_offset variable to track the offset when the irq check is skipped.
---
arch/m68k/hp300/time.c | 46 +++++++++++++++++++++++++-----------------
1 file changed, 27 insertions(+), 19 deletions(-)
diff --git a/arch/m68k/hp300/time.c b/arch/m68k/hp300/time.c
index 90982803a629..bfee13e1d0fe 100644
--- a/arch/m68k/hp300/time.c
+++ b/arch/m68k/hp300/time.c
@@ -30,7 +30,7 @@ static struct clocksource hp300_clk = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-static u32 clk_total;
+static u32 clk_total, clk_offset;
/* Clock hardware definitions */
@@ -41,9 +41,12 @@ static u32 clk_total;
#define CLKCR3 CLKCR1
#define CLKSR CLKCR2
#define CLKMSB1 0x5
+#define CLKLSB1 0x7
#define CLKMSB2 0x9
#define CLKMSB3 0xD
+#define CLKSR_INT1 BIT(0)
+
/* This is for machines which generate the exact clock. */
#define HP300_TIMER_CLOCK_FREQ 250000
@@ -60,6 +63,7 @@ static irqreturn_t hp300_tick(int irq, void *dev_id)
in_8(CLOCKBASE + CLKSR);
asm volatile ("movpw %1@(5),%0" : "=d" (tmp) : "a" (CLOCKBASE));
clk_total += INTVAL;
+ clk_offset = 0;
timer_routine(0, NULL);
local_irq_restore(flags);
@@ -70,24 +74,28 @@ static irqreturn_t hp300_tick(int irq, void *dev_id)
static u64 hp300_read_clk(struct clocksource *cs)
{
- unsigned long flags;
- unsigned char lsb, msb1, msb2;
- u32 ticks;
-
- local_irq_save(flags);
- /* Read current timer 1 value */
- msb1 = in_8(CLOCKBASE + 5);
- lsb = in_8(CLOCKBASE + 7);
- msb2 = in_8(CLOCKBASE + 5);
- if (msb1 != msb2)
- /* A carry happened while we were reading. Read it again */
- lsb = in_8(CLOCKBASE + 7);
-
- ticks = INTVAL - ((msb2 << 8) | lsb);
- ticks += clk_total;
- local_irq_restore(flags);
-
- return ticks;
+ unsigned long flags;
+ unsigned char lsb, msb, msb_new;
+ u32 ticks;
+
+ local_irq_save(flags);
+ /* Read current timer 1 value */
+ msb = in_8(CLOCKBASE + CLKMSB1);
+again:
+ if ((in_8(CLOCKBASE + CLKSR) & CLKSR_INT1) && msb > 0)
+ clk_offset = INTVAL;
+ lsb = in_8(CLOCKBASE + CLKLSB1);
+ msb_new = in_8(CLOCKBASE + CLKMSB1);
+ if (msb_new != msb) {
+ msb = msb_new;
+ goto again;
+ }
+
+ ticks = INTVAL - ((msb << 8) | lsb);
+ ticks += clk_offset + clk_total;
+ local_irq_restore(flags);
+
+ return ticks;
}
void __init hp300_sched_init(irq_handler_t vector)
--
2.18.1
next prev parent reply other threads:[~2018-12-01 1:00 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-01 0:53 [PATCH v4 00/14] m68k: Drop arch_gettimeoffset and adopt clocksource API Finn Thain
2018-12-01 0:53 ` [PATCH v4 05/14] m68k: amiga: Convert to " Finn Thain
2018-12-01 0:53 ` [PATCH v4 02/14] m68k: mac: Fix VIA timer counter accesses Finn Thain
2018-12-01 0:53 ` [PATCH v4 01/14] m68k: Call timer_interrupt() with interrupts disabled Finn Thain
2018-12-01 0:53 ` Finn Thain [this message]
2018-12-01 0:53 ` [PATCH v4 03/14] m68k: apollo, q40, sun3, sun3x: Remove arch_gettimeoffset implementations Finn Thain
2018-12-01 0:53 ` [PATCH v4 12/14] m68k: mvme147: Handle timer counter overflow Finn Thain
2018-12-01 0:53 ` [PATCH v4 13/14] m68k: mvme16x: Convert to clocksource API Finn Thain
2018-12-01 0:53 ` [PATCH v4 10/14] m68k: mac: " Finn Thain
2018-12-01 0:53 ` [PATCH v4 04/14] m68k: Drop ARCH_USES_GETTIMEOFFSET Finn Thain
2018-12-01 0:53 ` [PATCH v4 07/14] m68k: bvme6000: Convert to clocksource API Finn Thain
2018-12-01 0:53 ` [PATCH v4 14/14] m68k: mvme16x: Handle timer counter overflow Finn Thain
2018-12-01 0:53 ` [PATCH v4 08/14] m68k: hp300: Convert to clocksource API Finn Thain
2018-12-01 0:53 ` [PATCH v4 06/14] m68k: atari: " Finn Thain
2018-12-01 0:53 ` [PATCH v4 11/14] m68k: mvme147: " Finn Thain
2019-03-05 6:13 ` [PATCH v4 00/14] m68k: Drop arch_gettimeoffset and adopt " Finn Thain
2019-03-05 7:50 ` Geert Uytterhoeven
2019-03-05 9:55 ` Finn Thain
2019-03-05 12:01 ` Linus Walleij
2019-03-25 9:25 ` Geert Uytterhoeven
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