Hey all,
I've been working on improving performance of do_gettimeofday on
certain NUMA hardware (see my earlier tsc-disable posts for why the TSCs
cannot be used), and I wanted to run this by the list to make sure I'm
not doing anything too daft.
Mainly I'm concerned about my usage of bt_ioremap. Early in the boot
processes, I need to map in a couple of chipset registers and poke
values into them. However one of the registers needs to be kept mapped
for the life of the system (look for "cyclone_timer" below). I couldn't
find any documentation on whether memory mapped with bt_ioremap can be
held across mem_init(). It seems to "just work" but I wanted to find out
if I really should be re-mapping the register w/ ioremap once it becomes
available.
If you see any other issues with the patch, please let me know (I do
realize its a bit #ifdef happy, so go easy on that point).
Comments, suggestions and flames welcome
thanks
-john
PS: If you are so inclined/loony to actually try this patch, please note
that it depends on my tsc-disable_B2 patch to apply cleanly.
diff -Nru a/Documentation/Configure.help b/Documentation/Configure.help
--- a/Documentation/Configure.help Mon Jul 8 10:53:02 2002
+++ b/Documentation/Configure.help Mon Jul 8 10:53:02 2002
@@ -257,6 +257,11 @@
You will need a new lynxer.elf file to flash your firmware with - send
email to Martin.Bligh@us.ibm.com
+IBM Enterprise X-Architecture support
+CONFIG_X86_IBMEXA
+ This option makes use of a performance counter on the Cyclone chipset
+ for calculating do_gettimeofday, greatly improving its performance.
+
IO-APIC support on uniprocessors
CONFIG_X86_UP_IOAPIC
An IO-APIC (I/O Advanced Programmable Interrupt Controller) is an
diff -Nru a/arch/i386/config.in b/arch/i386/config.in
--- a/arch/i386/config.in Mon Jul 8 10:53:02 2002
+++ b/arch/i386/config.in Mon Jul 8 10:53:02 2002
@@ -201,6 +201,7 @@
bool 'Multi-node NUMA system support (Caution: Read help first)' CONFIG_X86_NUMA
if [ "$CONFIG_X86_NUMA" = "y" ]; then
bool 'Multiquad (IBM/Sequent) NUMAQ support' CONFIG_MULTIQUAD
+ bool 'IBM Enterprise X-Architecture support' CONFIG_X86_IBMEXA
fi
fi
diff -Nru a/arch/i386/kernel/time.c b/arch/i386/kernel/time.c
--- a/arch/i386/kernel/time.c Mon Jul 8 10:53:02 2002
+++ b/arch/i386/kernel/time.c Mon Jul 8 10:53:02 2002
@@ -253,6 +253,87 @@
static unsigned long (*do_gettimeoffset)(void) = do_slow_gettimeoffset;
+
+
+#ifdef CONFIG_X86_IBMEXA
+#define CYCLONE_CBAR_ADDR 0xFEB00CD0
+#define CYCLONE_PMCC_OFFSET 0x51A0
+#define CYCLONE_MPMC_OFFSET 0x51D0
+#define CYCLONE_MPCS_OFFSET 0x51A8
+#define CYCLONE_TIMER_FREQ 100000000
+static u32* cyclone_timer; /*Cyclone MPMC0 register*/
+static void init_cyclone_clock(void)
+{
+ u32* cyclone_cbar; /*Cyclone BaseAddr register*/
+ u32* cyclone_pmcc; /*Cyclone PMCC register*/
+ u32* cyclone_mpcs; /*Cyclone MPCS register*/
+ u32 base;
+
+ /*find base address*/
+ cyclone_cbar = bt_ioremap(CYCLONE_CBAR_ADDR, 4);
+ if(!cyclone_cbar) return;
+ base = *cyclone_cbar;
+ bt_iounmap(cyclone_cbar, 4);
+
+ /*setup PMCC*/
+ cyclone_pmcc = bt_ioremap(base + CYCLONE_PMCC_OFFSET, 8);
+ if(!cyclone_pmcc) return;
+ cyclone_pmcc[0] = 0x00000001;
+ bt_iounmap(cyclone_pmcc, 8);
+
+ /*setup MPCS*/
+ cyclone_mpcs = bt_ioremap(base + CYCLONE_MPCS_OFFSET, 8);
+ if(!cyclone_mpcs) return;
+ cyclone_mpcs[0] = 0x00000001;
+ bt_iounmap(cyclone_mpcs, 8);
+
+ /*map in cyclone_timer*/
+ cyclone_timer = bt_ioremap(base + CYCLONE_MPMC_OFFSET, 8);
+}
+
+static u32 last_cyclone_timer;
+
+static inline void mark_timeoffset_cyclone(void)
+{
+ int count;
+
+ /*quickly read the cyclone timer*/
+ if(cyclone_timer)
+ last_cyclone_timer = cyclone_timer[0];
+
+ /*calculate delay_at_last_interrupt*/
+ spin_lock(&i8253_lock);
+ outb_p(0x00, 0x43); /* latch the count ASAP */
+
+ count = inb_p(0x40); /* read the latched count */
+ count |= inb(0x40) << 8;
+ spin_unlock(&i8253_lock);
+
+ count = ((LATCH-1) - count) * TICK_SIZE;
+ delay_at_last_interrupt = (count + LATCH/2) / LATCH;
+}
+
+static unsigned long do_gettimeoffset_cyclone(void)
+{
+ u32 offset;
+
+ if(!cyclone_timer)
+ return delay_at_last_interrupt;
+
+ /* Read the cyclone timer */
+ offset = cyclone_timer[0];
+
+ /* .. relative to previous jiffy*/
+ offset = offset - last_cyclone_timer;
+
+ /*convert cyclone ticks to microseconds*/
+ offset = offset*(1000000/CYCLONE_TIMER_FREQ);
+
+ /* our adjusted time offset in microseconds */
+ return delay_at_last_interrupt + offset;
+}
+#endif /*CONFIG_X86_IBMEXA*/
+
#else
#define do_gettimeoffset() do_fast_gettimeoffset()
@@ -459,6 +540,7 @@
}
static int use_tsc;
+static int use_cyclone =1; /*XXX should be autodetected*/
/*
* This is the same as the above, except we _also_ save the current
@@ -506,6 +588,10 @@
count = ((LATCH-1) - count) * TICK_SIZE;
delay_at_last_interrupt = (count + LATCH/2) / LATCH;
}
+#ifdef CONFIG_X86_IBMEXA
+ if(use_cyclone)
+ mark_timeoffset_cyclone();
+#endif /*CONFIG_X86_IBMEXA*/
do_timer_interrupt(irq, NULL, regs);
@@ -695,6 +781,14 @@
}
}
}
+
+#ifdef CONFIG_X86_IBMEXA
+ if((!use_tsc) && use_cyclone){
+ printk("IBM EXA: Starting Cyclone Clock.\n");
+ do_gettimeoffset = do_gettimeoffset_cyclone;
+ init_cyclone_clock();
+ }
+#endif /*CONFIG_X86_IBMEXA*/
#ifdef CONFIG_VISWS
printk("Starting Cobalt Timer system clock\n");
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:14 EST