Commit 8531a35e authored by Kevin D. Kissell's avatar Kevin D. Kissell Committed by Ralf Baechle
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[MIPS] SMTC: Fix SMTC dyntick support.



Rework of SMTC support to make it work with the new clock event system,
allowing "tickless" operation, and to make it compatible with the use of
the "wait_irqoff" idle loop.  The new clocking scheme means that the
previously optional IPI instant replay mechanism is now required, and has
been made more robust.
Signed-off-by: default avatarKevin D. Kissell <kevink@paralogos.com>
Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent d2bb01b0
......@@ -1403,7 +1403,6 @@ config MIPS_MT_SMTC
depends on CPU_MIPS32_R2
#depends on CPU_MIPS64_R2 # once there is hardware ...
depends on SYS_SUPPORTS_MULTITHREADING
select GENERIC_CLOCKEVENTS_BROADCAST
select CPU_MIPSR2_IRQ_VI
select CPU_MIPSR2_IRQ_EI
select MIPS_MT
......@@ -1451,32 +1450,17 @@ config MIPS_VPE_LOADER
Includes a loader for loading an elf relocatable object
onto another VPE and running it.
config MIPS_MT_SMTC_INSTANT_REPLAY
bool "Low-latency Dispatch of Deferred SMTC IPIs"
depends on MIPS_MT_SMTC && !PREEMPT
default y
help
SMTC pseudo-interrupts between TCs are deferred and queued
if the target TC is interrupt-inhibited (IXMT). In the first
SMTC prototypes, these queued IPIs were serviced on return
to user mode, or on entry into the kernel idle loop. The
INSTANT_REPLAY option dispatches them as part of local_irq_restore()
processing, which adds runtime overhead (hence the option to turn
it off), but ensures that IPIs are handled promptly even under
heavy I/O interrupt load.
config MIPS_MT_SMTC_IM_BACKSTOP
bool "Use per-TC register bits as backstop for inhibited IM bits"
depends on MIPS_MT_SMTC
default y
default n
help
To support multiple TC microthreads acting as "CPUs" within
a VPE, VPE-wide interrupt mask bits must be specially manipulated
during interrupt handling. To support legacy drivers and interrupt
controller management code, SMTC has a "backstop" to track and
if necessary restore the interrupt mask. This has some performance
impact on interrupt service overhead. Disable it only if you know
what you are doing.
impact on interrupt service overhead.
config MIPS_MT_SMTC_IRQAFF
bool "Support IRQ affinity API"
......@@ -1486,10 +1470,8 @@ config MIPS_MT_SMTC_IRQAFF
Enables SMP IRQ affinity API (/proc/irq/*/smp_affinity, etc.)
for SMTC Linux kernel. Requires platform support, of which
an example can be found in the MIPS kernel i8259 and Malta
platform code. It is recommended that MIPS_MT_SMTC_INSTANT_REPLAY
be enabled if MIPS_MT_SMTC_IRQAFF is used. Adds overhead to
interrupt dispatch, and should be used only if you know what
you are doing.
platform code. Adds some overhead to interrupt dispatch, and
should be used only if you know what you are doing.
config MIPS_VPE_LOADER_TOM
bool "Load VPE program into memory hidden from linux"
......
......@@ -10,6 +10,7 @@ obj-y += cpu-probe.o branch.o entry.o genex.o irq.o process.o \
obj-$(CONFIG_CEVT_BCM1480) += cevt-bcm1480.o
obj-$(CONFIG_CEVT_R4K) += cevt-r4k.o
obj-$(CONFIG_MIPS_MT_SMTC) += cevt-smtc.o
obj-$(CONFIG_CEVT_DS1287) += cevt-ds1287.o
obj-$(CONFIG_CEVT_GT641XX) += cevt-gt641xx.o
obj-$(CONFIG_CEVT_SB1250) += cevt-sb1250.o
......
......@@ -12,6 +12,14 @@
#include <asm/smtc_ipi.h>
#include <asm/time.h>
#include <asm/cevt-r4k.h>
/*
* The SMTC Kernel for the 34K, 1004K, et. al. replaces several
* of these routines with SMTC-specific variants.
*/
#ifndef CONFIG_MIPS_MT_SMTC
static int mips_next_event(unsigned long delta,
struct clock_event_device *evt)
......@@ -19,60 +27,27 @@ static int mips_next_event(unsigned long delta,
unsigned int cnt;
int res;
#ifdef CONFIG_MIPS_MT_SMTC
{
unsigned long flags, vpflags;
local_irq_save(flags);
vpflags = dvpe();
#endif
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
res = ((int)(read_c0_count() - cnt) > 0) ? -ETIME : 0;
#ifdef CONFIG_MIPS_MT_SMTC
evpe(vpflags);
local_irq_restore(flags);
}
#endif
return res;
}
static void mips_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
#endif /* CONFIG_MIPS_MT_SMTC */
void mips_set_clock_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
/* Nothing to do ... */
}
static DEFINE_PER_CPU(struct clock_event_device, mips_clockevent_device);
static int cp0_timer_irq_installed;
DEFINE_PER_CPU(struct clock_event_device, mips_clockevent_device);
int cp0_timer_irq_installed;
/*
* Timer ack for an R4k-compatible timer of a known frequency.
*/
static void c0_timer_ack(void)
{
write_c0_compare(read_c0_compare());
}
#ifndef CONFIG_MIPS_MT_SMTC
/*
* Possibly handle a performance counter interrupt.
* Return true if the timer interrupt should not be checked
*/
static inline int handle_perf_irq(int r2)
{
/*
* The performance counter overflow interrupt may be shared with the
* timer interrupt (cp0_perfcount_irq < 0). If it is and a
* performance counter has overflowed (perf_irq() == IRQ_HANDLED)
* and we can't reliably determine if a counter interrupt has also
* happened (!r2) then don't check for a timer interrupt.
*/
return (cp0_perfcount_irq < 0) &&
perf_irq() == IRQ_HANDLED &&
!r2;
}
static irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
{
const int r2 = cpu_has_mips_r2;
struct clock_event_device *cd;
......@@ -93,12 +68,8 @@ static irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
* interrupt. Being the paranoiacs we are we check anyway.
*/
if (!r2 || (read_c0_cause() & (1 << 30))) {
c0_timer_ack();
#ifdef CONFIG_MIPS_MT_SMTC
if (cpu_data[cpu].vpe_id)
goto out;
cpu = 0;
#endif
/* Clear Count/Compare Interrupt */
write_c0_compare(read_c0_compare());
cd = &per_cpu(mips_clockevent_device, cpu);
cd->event_handler(cd);
}
......@@ -107,65 +78,16 @@ out:
return IRQ_HANDLED;
}
static struct irqaction c0_compare_irqaction = {
#endif /* Not CONFIG_MIPS_MT_SMTC */
struct irqaction c0_compare_irqaction = {
.handler = c0_compare_interrupt,
#ifdef CONFIG_MIPS_MT_SMTC
.flags = IRQF_DISABLED,
#else
.flags = IRQF_DISABLED | IRQF_PERCPU,
#endif
.name = "timer",
};
#ifdef CONFIG_MIPS_MT_SMTC
DEFINE_PER_CPU(struct clock_event_device, smtc_dummy_clockevent_device);
static void smtc_set_mode(enum clock_event_mode mode,
struct clock_event_device *evt)
{
}
static void mips_broadcast(cpumask_t mask)
{
unsigned int cpu;
for_each_cpu_mask(cpu, mask)
smtc_send_ipi(cpu, SMTC_CLOCK_TICK, 0);
}
static void setup_smtc_dummy_clockevent_device(void)
{
//uint64_t mips_freq = mips_hpt_^frequency;
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
cd = &per_cpu(smtc_dummy_clockevent_device, cpu);
cd->name = "SMTC";
cd->features = CLOCK_EVT_FEAT_DUMMY;
/* Calculate the min / max delta */
cd->mult = 0; //div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
cd->shift = 0; //32;
cd->max_delta_ns = 0; //clockevent_delta2ns(0x7fffffff, cd);
cd->min_delta_ns = 0; //clockevent_delta2ns(0x30, cd);
cd->rating = 200;
cd->irq = 17; //-1;
// if (cpu)
// cd->cpumask = CPU_MASK_ALL; // cpumask_of_cpu(cpu);
// else
cd->cpumask = cpumask_of_cpu(cpu);
cd->set_mode = smtc_set_mode;
cd->broadcast = mips_broadcast;
clockevents_register_device(cd);
}
#endif
static void mips_event_handler(struct clock_event_device *dev)
void mips_event_handler(struct clock_event_device *dev)
{
}
......@@ -177,7 +99,23 @@ static int c0_compare_int_pending(void)
return (read_c0_cause() >> cp0_compare_irq) & 0x100;
}
static int c0_compare_int_usable(void)
/*
* Compare interrupt can be routed and latched outside the core,
* so a single execution hazard barrier may not be enough to give
* it time to clear as seen in the Cause register. 4 time the
* pipeline depth seems reasonably conservative, and empirically
* works better in configurations with high CPU/bus clock ratios.
*/
#define compare_change_hazard() \
do { \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
irq_disable_hazard(); \
} while (0)
int c0_compare_int_usable(void)
{
unsigned int delta;
unsigned int cnt;
......@@ -187,7 +125,7 @@ static int c0_compare_int_usable(void)
*/
if (c0_compare_int_pending()) {
write_c0_compare(read_c0_count());
irq_disable_hazard();
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
}
......@@ -196,7 +134,7 @@ static int c0_compare_int_usable(void)
cnt = read_c0_count();
cnt += delta;
write_c0_compare(cnt);
irq_disable_hazard();
compare_change_hazard();
if ((int)(read_c0_count() - cnt) < 0)
break;
/* increase delta if the timer was already expired */
......@@ -205,11 +143,12 @@ static int c0_compare_int_usable(void)
while ((int)(read_c0_count() - cnt) <= 0)
; /* Wait for expiry */
compare_change_hazard();
if (!c0_compare_int_pending())
return 0;
write_c0_compare(read_c0_count());
irq_disable_hazard();
compare_change_hazard();
if (c0_compare_int_pending())
return 0;
......@@ -219,6 +158,8 @@ static int c0_compare_int_usable(void)
return 1;
}
#ifndef CONFIG_MIPS_MT_SMTC
int __cpuinit mips_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
......@@ -229,17 +170,6 @@ int __cpuinit mips_clockevent_init(void)
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
#ifdef CONFIG_MIPS_MT_SMTC
setup_smtc_dummy_clockevent_device();
/*
* On SMTC we only register VPE0's compare interrupt as clockevent
* device.
*/
if (cpu)
return 0;
#endif
if (!c0_compare_int_usable())
return -ENXIO;
......@@ -265,13 +195,9 @@ int __cpuinit mips_clockevent_init(void)
cd->rating = 300;
cd->irq = irq;
#ifdef CONFIG_MIPS_MT_SMTC
cd->cpumask = CPU_MASK_ALL;
#else
cd->cpumask = cpumask_of_cpu(cpu);
#endif
cd->set_next_event = mips_next_event;
cd->set_mode = mips_set_mode;
cd->set_mode = mips_set_clock_mode;
cd->event_handler = mips_event_handler;
clockevents_register_device(cd);
......@@ -281,12 +207,9 @@ int __cpuinit mips_clockevent_init(void)
cp0_timer_irq_installed = 1;
#ifdef CONFIG_MIPS_MT_SMTC
#define CPUCTR_IMASKBIT (0x100 << cp0_compare_irq)
setup_irq_smtc(irq, &c0_compare_irqaction, CPUCTR_IMASKBIT);
#else
setup_irq(irq, &c0_compare_irqaction);
#endif
return 0;
}
#endif /* Not CONFIG_MIPS_MT_SMTC */
/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2007 MIPS Technologies, Inc.
* Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
* Copyright (C) 2008 Kevin D. Kissell, Paralogos sarl
*/
#include <linux/clockchips.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <asm/smtc_ipi.h>
#include <asm/time.h>
#include <asm/cevt-r4k.h>
/*
* Variant clock event timer support for SMTC on MIPS 34K, 1004K
* or other MIPS MT cores.
*
* Notes on SMTC Support:
*
* SMTC has multiple microthread TCs pretending to be Linux CPUs.
* But there's only one Count/Compare pair per VPE, and Compare
* interrupts are taken opportunisitically by available TCs
* bound to the VPE with the Count register. The new timer
* framework provides for global broadcasts, but we really
* want VPE-level multicasts for best behavior. So instead
* of invoking the high-level clock-event broadcast code,
* this version of SMTC support uses the historical SMTC
* multicast mechanisms "under the hood", appearing to the
* generic clock layer as if the interrupts are per-CPU.
*
* The approach taken here is to maintain a set of NR_CPUS
* virtual timers, and track which "CPU" needs to be alerted
* at each event.
*
* It's unlikely that we'll see a MIPS MT core with more than
* 2 VPEs, but we *know* that we won't need to handle more
* VPEs than we have "CPUs". So NCPUs arrays of NCPUs elements
* is always going to be overkill, but always going to be enough.
*/
unsigned long smtc_nexttime[NR_CPUS][NR_CPUS];
static int smtc_nextinvpe[NR_CPUS];
/*
* Timestamps stored are absolute values to be programmed
* into Count register. Valid timestamps will never be zero.
* If a Zero Count value is actually calculated, it is converted
* to be a 1, which will introduce 1 or two CPU cycles of error
* roughly once every four billion events, which at 1000 HZ means
* about once every 50 days. If that's actually a problem, one
* could alternate squashing 0 to 1 and to -1.
*/
#define MAKEVALID(x) (((x) == 0L) ? 1L : (x))
#define ISVALID(x) ((x) != 0L)
/*
* Time comparison is subtle, as it's really truncated
* modular arithmetic.
*/
#define IS_SOONER(a, b, reference) \
(((a) - (unsigned long)(reference)) < ((b) - (unsigned long)(reference)))
/*
* CATCHUP_INCREMENT, used when the function falls behind the counter.
* Could be an increasing function instead of a constant;
*/
#define CATCHUP_INCREMENT 64
static int mips_next_event(unsigned long delta,
struct clock_event_device *evt)
{
unsigned long flags;
unsigned int mtflags;
unsigned long timestamp, reference, previous;
unsigned long nextcomp = 0L;
int vpe = current_cpu_data.vpe_id;
int cpu = smp_processor_id();
local_irq_save(flags);
mtflags = dmt();
/*
* Maintain the per-TC virtual timer
* and program the per-VPE shared Count register
* as appropriate here...
*/
reference = (unsigned long)read_c0_count();
timestamp = MAKEVALID(reference + delta);
/*
* To really model the clock, we have to catch the case
* where the current next-in-VPE timestamp is the old
* timestamp for the calling CPE, but the new value is
* in fact later. In that case, we have to do a full
* scan and discover the new next-in-VPE CPU id and
* timestamp.
*/
previous = smtc_nexttime[vpe][cpu];
if (cpu == smtc_nextinvpe[vpe] && ISVALID(previous)
&& IS_SOONER(previous, timestamp, reference)) {
int i;
int soonest = cpu;
/*
* Update timestamp array here, so that new
* value gets considered along with those of
* other virtual CPUs on the VPE.
*/
smtc_nexttime[vpe][cpu] = timestamp;
for_each_online_cpu(i) {
if (ISVALID(smtc_nexttime[vpe][i])
&& IS_SOONER(smtc_nexttime[vpe][i],
smtc_nexttime[vpe][soonest], reference)) {
soonest = i;
}
}
smtc_nextinvpe[vpe] = soonest;
nextcomp = smtc_nexttime[vpe][soonest];
/*
* Otherwise, we don't have to process the whole array rank,
* we just have to see if the event horizon has gotten closer.
*/
} else {
if (!ISVALID(smtc_nexttime[vpe][smtc_nextinvpe[vpe]]) ||
IS_SOONER(timestamp,
smtc_nexttime[vpe][smtc_nextinvpe[vpe]], reference)) {
smtc_nextinvpe[vpe] = cpu;
nextcomp = timestamp;
}
/*
* Since next-in-VPE may me the same as the executing
* virtual CPU, we update the array *after* checking
* its value.
*/
smtc_nexttime[vpe][cpu] = timestamp;
}
/*
* It may be that, in fact, we don't need to update Compare,
* but if we do, we want to make sure we didn't fall into
* a crack just behind Count.
*/
if (ISVALID(nextcomp)) {
write_c0_compare(nextcomp);
ehb();
/*
* We never return an error, we just make sure
* that we trigger the handlers as quickly as
* we can if we fell behind.
*/
while ((nextcomp - (unsigned long)read_c0_count())
> (unsigned long)LONG_MAX) {
nextcomp += CATCHUP_INCREMENT;
write_c0_compare(nextcomp);
ehb();
}
}
emt(mtflags);
local_irq_restore(flags);
return 0;
}
void smtc_distribute_timer(int vpe)
{
unsigned long flags;
unsigned int mtflags;
int cpu;
struct clock_event_device *cd;
unsigned long nextstamp = 0L;
unsigned long reference;
repeat:
for_each_online_cpu(cpu) {
/*
* Find virtual CPUs within the current VPE who have
* unserviced timer requests whose time is now past.
*/
local_irq_save(flags);
mtflags = dmt();
if (cpu_data[cpu].vpe_id == vpe &&
ISVALID(smtc_nexttime[vpe][cpu])) {
reference = (unsigned long)read_c0_count();
if ((smtc_nexttime[vpe][cpu] - reference)
> (unsigned long)LONG_MAX) {
smtc_nexttime[vpe][cpu] = 0L;
emt(mtflags);
local_irq_restore(flags);
/*
* We don't send IPIs to ourself.
*/
if (cpu != smp_processor_id()) {
smtc_send_ipi(cpu, SMTC_CLOCK_TICK, 0);
} else {
cd = &per_cpu(mips_clockevent_device, cpu);
cd->event_handler(cd);
}
} else {
/* Local to VPE but Valid Time not yet reached. */
if (!ISVALID(nextstamp) ||
IS_SOONER(smtc_nexttime[vpe][cpu], nextstamp,
reference)) {
smtc_nextinvpe[vpe] = cpu;
nextstamp = smtc_nexttime[vpe][cpu];
}
emt(mtflags);
local_irq_restore(flags);
}
} else {
emt(mtflags);
local_irq_restore(flags);
}
}
/* Reprogram for interrupt at next soonest timestamp for VPE */
if (ISVALID(nextstamp)) {
write_c0_compare(nextstamp);
ehb();
if ((nextstamp - (unsigned long)read_c0_count())
> (unsigned long)LONG_MAX)
goto repeat;
}
}
irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
{
int cpu = smp_processor_id();
/* If we're running SMTC, we've got MIPS MT and therefore MIPS32R2 */
handle_perf_irq(1);
if (read_c0_cause() & (1 << 30)) {
/* Clear Count/Compare Interrupt */
write_c0_compare(read_c0_compare());
smtc_distribute_timer(cpu_data[cpu].vpe_id);
}
return IRQ_HANDLED;
}
int __cpuinit mips_clockevent_init(void)
{
uint64_t mips_freq = mips_hpt_frequency;
unsigned int cpu = smp_processor_id();
struct clock_event_device *cd;
unsigned int irq;
int i;
int j;
if (!cpu_has_counter || !mips_hpt_frequency)
return -ENXIO;
if (cpu == 0) {
for (i = 0; i < num_possible_cpus(); i++) {
smtc_nextinvpe[i] = 0;
for (j = 0; j < num_possible_cpus(); j++)
smtc_nexttime[i][j] = 0L;
}
/*
* SMTC also can't have the usablility test
* run by secondary TCs once Compare is in use.
*/
if (!c0_compare_int_usable())
return -ENXIO;
}
/*
* With vectored interrupts things are getting platform specific.
* get_c0_compare_int is a hook to allow a platform to return the
* interrupt number of it's liking.
*/
irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
if (get_c0_compare_int)
irq = get_c0_compare_int();
cd = &per_cpu(mips_clockevent_device, cpu);
cd->name = "MIPS";
cd->features = CLOCK_EVT_FEAT_ONESHOT;
/* Calculate the min / max delta */
cd->mult = div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);