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Re: 2.6.19 timer API changes

To: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Subject: Re: 2.6.19 timer API changes
From: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Date: Wed, 20 Dec 2006 17:29:25 +0300
Cc: danieljlaird@hotmail.com, linux-mips@linux-mips.org, ralf@linux-mips.org
In-reply-to: <20061220.021508.97296486.anemo@mba.ocn.ne.jp>
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Hello.

Atsushi Nemoto wrote:

I am just digging out the mips core user manual... However I have tried this change you suggested, it still takes a long time
to get past the calibrate delay function (~10seconds).
However after this it seems to run at full speed where as before it used to
run very slow.
So an improvement, I think this does mean the new time.c has broken 8550
support hopefully I can find otu what the core does so it can be fixed.

Hm, then it seems writing to COMPARE does not clear COUNT.

   Looks like the count/compare match does this...

How about this?  You should still fix pnx8550_hpt_read() anyway, but I
suppose gettimeofday() on PNX8550 was broken long time.

   And nobody noticed. :-)

Subject: [MIPS] Use custom timer_ack and clocksource_mips.read for PNX8550

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
---
diff --git a/arch/mips/kernel/time.c b/arch/mips/kernel/time.c
index 11aab6d..8aa544f 100644
--- a/arch/mips/kernel/time.c
+++ b/arch/mips/kernel/time.c
@@ -94,10 +94,8 @@ static void c0_timer_ack(void)
 {
        unsigned int count;
-#ifndef CONFIG_SOC_PNX8550 /* pnx8550 resets to zero */
        /* Ack this timer interrupt and set the next one.  */
        expirelo += cycles_per_jiffy;
-#endif
        write_c0_compare(expirelo);
/* Check to see if we have missed any timer interrupts. */
diff --git a/arch/mips/philips/pnx8550/common/time.c 
b/arch/mips/philips/pnx8550/common/time.c
index 65c440e..e86905a 100644
--- a/arch/mips/philips/pnx8550/common/time.c
+++ b/arch/mips/philips/pnx8550/common/time.c
@@ -33,7 +33,18 @@ #include <asm/debug.h>
 #include <int.h>
 #include <cm.h>

-extern unsigned int mips_hpt_frequency;
+static unsigned long cycles_per_jiffy __read_mostly;

  I wonder shouldn't it be added to <asm-mips/time.h> just for such occasions..

+
+static void pnx8550_timer_ack(void)
+{
+       write_c0_compare(cycles_per_jiffy);
+}
+
+static cycle_t pnx8550_hpt_read(void)
+{
+       /* FIXME: we should use timer2 or timer3 as freerun counter */
+       return read_c0_count();
> +}

I'd suggest read_c0_count2() here, possibly adding an interrupt handler for it since it will interrupt upon hitting compare2 reg. value (but we could probably just mask the IRQ off), and enabling the timer 2, of course (the current code disables it)...

WBR, Sergei

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