[Qemu-devel] [PATCH v11 0/7] PTimer fixes/features and ARM MPTimer conversion

[Qemu-devel] [PATCH v11 0/7] PTimer fixes/features and ARM MPTimer conversion

[Dmitry Osipenko]

Changelog for ARM MPTimer QEMUTimer to ptimer conversion:

    V2: Fixed changing periodic timer counter value "on the fly". I added a
        test to the gist to cover that issue.

    V3: Fixed starting the timer with load = 0 and counter != 0, added tests
        to the gist for this issue. Changed vmstate version for all VMSD's,
        since loadvm doesn't check version of nested VMSD.

    V4: Fixed spurious IT bit set for the timer starting in the periodic mode
        with counter = 0. Test added.

    V5: Code cleanup, now depends on ptimer_set_limit() fix.

    V6: No code change, added test to check ptimer_get_count() with corrected
        .limit value.

    V7: No change.

    V8: No change.

    V9: No change.

    V10: Correctly handle cases when counter = load = 0 and prescaler != 0,
         i.e. triggering interrupt in that case. Call ptimer_* only when
         certain MPTimer state was changed, like prescaler change. Factor out
         timerblock_set_count from timerblock_run and inline both.
         Tests updated.

    V11: Fixed missed periodic timer stopping on setting counter => 0 with
         load = 0 and prescaler = 0.

ARM MPTimer tests: https://gist.github.com/digetx/dbd46109503b1a91941a


Patches for ptimer are introduced since V5 of "ARM MPTimer conversion".

Changelog for the ptimer patches:

    V5: Only fixed ptimer_set_limit() for the disabled timer.

    V6: As was pointed by Peter Maydell, there are other issues beyond
        ptimer_set_limit(), so V6 supposed to cover all those issues.

    V7: Added accidentally removed !use_icount check.
        Added missed "else" statement.

    V8: Adjust period instead of the limit and do it for periodic timer only
        (.limit adjusting bug). Added patch/fix for freq/period change and
        ptimer_get_count() improvement.

    V9: Don't do wrap around if counter == 0, otherwise polled periodic
        timer won't ever return counter = 0.

    V10: Addressed V8/9 review comments.
         Adjust timer period based on delta instead of limit.
         Don't wrap around when in icount mode.
         New patches: "on the fly" mode switch, silence error msg when
                      delta = load = 0, introduce ptimer_get_limit.

    V11: Dropped timer tick from "Perform tick and counter wrap around if
         timer already expired" patch since it would cause bogus tick after
         QEMU been reset if ptimer was stopped and it's QEMUtimer expired
         during reset.
         Patch "Legalize running with delta = load = 0" now explicitly
         forbids period = 0.

Dmitry Osipenko (7):
  hw/ptimer: Fix issues caused by the adjusted timer limit value
  hw/ptimer: Perform counter wrap around if timer already expired
  hw/ptimer: Update .delta on period/freq change
  hw/ptimer: Support "on the fly" timer mode switch
  hw/ptimer: Introduce ptimer_get_limit
  hw/ptimer: Legalize running with delta = load = 0 and abort on period
    = 0
  arm_mptimer: Convert to use ptimer

 hw/core/ptimer.c               | 111 ++++++++++++++++++++--------------
 hw/timer/arm_mptimer.c         | 131 +++++++++++++++++++++--------------------
 include/hw/ptimer.h            |   1 +
 include/hw/timer/arm_mptimer.h |   5 +-
 4 files changed, 135 insertions(+), 113 deletions(-)

-- 
2.7.0

[Qemu-devel] [PATCH v11 1/7] hw/ptimer: Fix issues caused by the adjusted timer limit value

[Dmitry Osipenko]

Multiple issues here related to the timer with a adjusted .limit value:

1) ptimer_get_count() returns incorrect counter value for the disabled
timer after loading the counter with a small value, because adjusted limit
value is used instead of the original.

For instance:
    1) ptimer_stop(t)
    2) ptimer_set_period(t, 1)
    3) ptimer_set_limit(t, 0, 1)
    4) ptimer_get_count(t) <-- would return 10000 instead of 0

2) ptimer_get_count() might return incorrect value for the timer running
with a adjusted limit value.

For instance:
    1) ptimer_stop(t)
    2) ptimer_set_period(t, 1)
    3) ptimer_set_limit(t, 10, 1)
    4) ptimer_run(t)
    5) ptimer_get_count(t) <-- might return value > 10

3) Neither ptimer_set_period() nor ptimer_set_freq() are adjusting the
limit value, so it is still possible to make timer timeout value
arbitrary small.

For instance:
    1) ptimer_set_period(t, 10000)
    2) ptimer_set_limit(t, 1, 0)
    3) ptimer_set_period(t, 1) <-- bypass limit correction

Fix all of the above issues by adjusting timer period instead of the limit.
Perform the adjustment for periodic timer only. Use the delta value instead
of the limit to make decision whether adjustment is required, as limit could
be altered while timer is running, resulting in incorrect value returned by
ptimer_get_count.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
---
 hw/core/ptimer.c | 51 +++++++++++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 20 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index edf077c..6dc1677 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -34,6 +34,9 @@ static void ptimer_trigger(ptimer_state *s)
 
 static void ptimer_reload(ptimer_state *s)
 {
+    uint32_t period_frac = s->period_frac;
+    uint64_t period = s->period;
+
     if (s->delta == 0) {
         ptimer_trigger(s);
         s->delta = s->limit;
@@ -44,10 +47,24 @@ static void ptimer_reload(ptimer_state *s)
         return;
     }
 
+    /*
+     * Artificially limit timeout rate to something
+     * achievable under QEMU.  Otherwise, QEMU spends all
+     * its time generating timer interrupts, and there
+     * is no forward progress.
+     * About ten microseconds is the fastest that really works
+     * on the current generation of host machines.
+     */
+
+    if ((s->enabled == 1) && (s->delta * period < 10000) && !use_icount) {
+        period = 10000 / s->delta;
+        period_frac = 0;
+    }
+
     s->last_event = s->next_event;
-    s->next_event = s->last_event + s->delta * s->period;
-    if (s->period_frac) {
-        s->next_event += ((int64_t)s->period_frac * s->delta) >> 32;
+    s->next_event = s->last_event + s->delta * period;
+    if (period_frac) {
+        s->next_event += ((int64_t)period_frac * s->delta) >> 32;
     }
     timer_mod(s->timer, s->next_event);
 }
@@ -82,6 +99,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
             uint64_t div;
             int clz1, clz2;
             int shift;
+            uint32_t period_frac = s->period_frac;
+            uint64_t period = s->period;
+
+            if ((s->enabled == 1) && !use_icount && (s->delta * period < 10000)) {
+                period = 10000 / s->delta;
+                period_frac = 0;
+            }
 
             /* We need to divide time by period, where time is stored in
                rem (64-bit integer) and period is stored in period/period_frac
@@ -94,7 +118,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
             */
 
             rem = s->next_event - now;
-            div = s->period;
+            div = period;
 
             clz1 = clz64(rem);
             clz2 = clz64(div);
@@ -103,13 +127,13 @@ uint64_t ptimer_get_count(ptimer_state *s)
             rem <<= shift;
             div <<= shift;
             if (shift >= 32) {
-                div |= ((uint64_t)s->period_frac << (shift - 32));
+                div |= ((uint64_t)period_frac << (shift - 32));
             } else {
                 if (shift != 0)
-                    div |= (s->period_frac >> (32 - shift));
+                    div |= (period_frac >> (32 - shift));
                 /* Look at remaining bits of period_frac and round div up if 
                    necessary.  */
-                if ((uint32_t)(s->period_frac << shift))
+                if ((uint32_t)(period_frac << shift))
                     div += 1;
             }
             counter = rem / div;
@@ -181,19 +205,6 @@ void ptimer_set_freq(ptimer_state *s, uint32_t freq)
    count = limit.  */
 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
 {
-    /*
-     * Artificially limit timeout rate to something
-     * achievable under QEMU.  Otherwise, QEMU spends all
-     * its time generating timer interrupts, and there
-     * is no forward progress.
-     * About ten microseconds is the fastest that really works
-     * on the current generation of host machines.
-     */
-
-    if (!use_icount && limit * s->period < 10000 && s->period) {
-        limit = 10000 / s->period;
-    }
-
     s->limit = limit;
     if (reload)
         s->delta = limit;
-- 
2.7.0

[Qemu-devel] [PATCH v11 2/7] hw/ptimer: Perform counter wrap around if timer already expired

[Dmitry Osipenko]

ptimer_get_count() might be called while QEMU timer already been expired.
In that case ptimer would return counter = 0, which might be undesirable
in case of polled timer. Do counter wrap around for periodic timer to keep
it distributed. In order to achieve more accurate emulation behaviour of
certain hardware, don't perform wrap around when in icount mode and return
counter = 0 in that case (that doesn't affect polled counter distribution).

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/core/ptimer.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index 6dc1677..cb50d30 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -83,14 +83,16 @@ static void ptimer_tick(void *opaque)
 
 uint64_t ptimer_get_count(ptimer_state *s)
 {
-    int64_t now;
     uint64_t counter;
 
     if (s->enabled) {
-        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        int64_t next = s->next_event;
+        bool expired = (now - next >= 0);
+        bool oneshot = (s->enabled == 2);
+
         /* Figure out the current counter value.  */
-        if (now - s->next_event > 0
-            || s->period == 0) {
+        if (s->period == 0 || (expired && (oneshot || use_icount))) {
             /* Prevent timer underflowing if it should already have
                triggered.  */
             counter = 0;
@@ -102,7 +104,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
             uint32_t period_frac = s->period_frac;
             uint64_t period = s->period;
 
-            if ((s->enabled == 1) && !use_icount && (s->delta * period < 10000)) {
+            if (!oneshot && (s->delta * period < 10000) && !use_icount) {
                 period = 10000 / s->delta;
                 period_frac = 0;
             }
@@ -117,7 +119,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
                backwards.
             */
 
-            rem = s->next_event - now;
+            rem = expired ? now - next : next - now;
             div = period;
 
             clz1 = clz64(rem);
@@ -137,6 +139,11 @@ uint64_t ptimer_get_count(ptimer_state *s)
                     div += 1;
             }
             counter = rem / div;
+
+            if (expired && (counter != 0)) {
+                /* Wrap around periodic counter.  */
+                counter = s->limit - counter % s->limit;
+            }
         }
     } else {
         counter = s->delta;
-- 
2.7.0

[Qemu-devel] [PATCH v11 3/7] hw/ptimer: Update .delta on period/freq change

[Dmitry Osipenko]

Delta value must be updated on period/freq change, otherwise running timer
would be restarted (counter reloaded with old delta). Only m68k/mcf520x
and arm/arm_timer devices are currently doing freq change correctly, i.e.
stopping the timer. Perform delta update to fix affected devices and
eliminate potential further mistakes.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
---
 hw/core/ptimer.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index cb50d30..904a77b 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -189,6 +189,7 @@ void ptimer_stop(ptimer_state *s)
 /* Set counter increment interval in nanoseconds.  */
 void ptimer_set_period(ptimer_state *s, int64_t period)
 {
+    s->delta = ptimer_get_count(s);
     s->period = period;
     s->period_frac = 0;
     if (s->enabled) {
@@ -200,6 +201,7 @@ void ptimer_set_period(ptimer_state *s, int64_t period)
 /* Set counter frequency in Hz.  */
 void ptimer_set_freq(ptimer_state *s, uint32_t freq)
 {
+    s->delta = ptimer_get_count(s);
     s->period = 1000000000ll / freq;
     s->period_frac = (1000000000ll << 32) / freq;
     if (s->enabled) {
-- 
2.7.0

[Qemu-devel] [PATCH v11 4/7] hw/ptimer: Support "on the fly" timer mode switch

[Dmitry Osipenko]

Allow switching between periodic <-> oneshot modes while timer is running.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
---
 hw/core/ptimer.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index 904a77b..a85d1ae 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -162,16 +162,17 @@ void ptimer_set_count(ptimer_state *s, uint64_t count)
 
 void ptimer_run(ptimer_state *s, int oneshot)
 {
-    if (s->enabled) {
-        return;
-    }
-    if (s->period == 0) {
+    bool was_disabled = !s->enabled;
+
+    if (was_disabled && s->period == 0) {
         fprintf(stderr, "Timer with period zero, disabling\n");
         return;
     }
     s->enabled = oneshot ? 2 : 1;
-    s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-    ptimer_reload(s);
+    if (was_disabled) {
+        s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        ptimer_reload(s);
+    }
 }
 
 /* Pause a timer.  Note that this may cause it to "lose" time, even if it
-- 
2.7.0

[Qemu-devel] [PATCH v11 5/7] hw/ptimer: Introduce ptimer_get_limit

[Dmitry Osipenko]

Currently ptimer users are used to store copy of the limit value, because
ptimer doesn't provide facility to retrieve the limit. Let's provide it.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>
---
 hw/core/ptimer.c    | 5 +++++
 include/hw/ptimer.h | 1 +
 2 files changed, 6 insertions(+)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index a85d1ae..142cc64 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -224,6 +224,11 @@ void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload)
     }
 }
 
+uint64_t ptimer_get_limit(ptimer_state *s)
+{
+    return s->limit;
+}
+
 const VMStateDescription vmstate_ptimer = {
     .name = "ptimer",
     .version_id = 1,
diff --git a/include/hw/ptimer.h b/include/hw/ptimer.h
index 8ebacbb..e397db5 100644
--- a/include/hw/ptimer.h
+++ b/include/hw/ptimer.h
@@ -19,6 +19,7 @@ typedef void (*ptimer_cb)(void *opaque);
 ptimer_state *ptimer_init(QEMUBH *bh);
 void ptimer_set_period(ptimer_state *s, int64_t period);
 void ptimer_set_freq(ptimer_state *s, uint32_t freq);
+uint64_t ptimer_get_limit(ptimer_state *s);
 void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload);
 uint64_t ptimer_get_count(ptimer_state *s);
 void ptimer_set_count(ptimer_state *s, uint64_t count);
-- 
2.7.0

[Qemu-devel] [PATCH v11 6/7] hw/ptimer: Legalize running with delta = load = 0 and abort on period = 0

[Dmitry Osipenko]

Currently ptimer would print error message and clear enable flag for an
arming timer that has delta = load = 0. That actually could be a valid case
for some hardware, like instant IRQ trigger for oneshot timer or continuous
in periodic mode. Support those cases by removing the error message and
stopping the timer when delta = 0. Abort execution when period = 0 instead
of printing the error message, otherwise there is a chance to miss that error.

In addition, don't re-load oneshot timer when delta = 0 and remove duplicated
code from ptimer_tick(), since ptimer_reload would invoke trigger and stop
the timer.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/core/ptimer.c | 27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
index 142cc64..cec59e1 100644
--- a/hw/core/ptimer.c
+++ b/hw/core/ptimer.c
@@ -39,11 +39,14 @@ static void ptimer_reload(ptimer_state *s)
 
     if (s->delta == 0) {
         ptimer_trigger(s);
+    }
+
+    if (s->delta == 0 && s->enabled == 1) {
         s->delta = s->limit;
     }
-    if (s->delta == 0 || s->period == 0) {
-        fprintf(stderr, "Timer with period zero, disabling\n");
-        s->enabled = 0;
+
+    if (s->delta == 0) {
+        ptimer_stop(s);
         return;
     }
 
@@ -72,27 +75,22 @@ static void ptimer_reload(ptimer_state *s)
 static void ptimer_tick(void *opaque)
 {
     ptimer_state *s = (ptimer_state *)opaque;
-    ptimer_trigger(s);
     s->delta = 0;
-    if (s->enabled == 2) {
-        s->enabled = 0;
-    } else {
-        ptimer_reload(s);
-    }
+    ptimer_reload(s);
 }
 
 uint64_t ptimer_get_count(ptimer_state *s)
 {
     uint64_t counter;
 
-    if (s->enabled) {
+    if (s->enabled && s->delta != 0) {
         int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
         int64_t next = s->next_event;
         bool expired = (now - next >= 0);
         bool oneshot = (s->enabled == 2);
 
         /* Figure out the current counter value.  */
-        if (s->period == 0 || (expired && (oneshot || use_icount))) {
+        if (expired && (oneshot || use_icount)) {
             /* Prevent timer underflowing if it should already have
                triggered.  */
             counter = 0;
@@ -164,10 +162,7 @@ void ptimer_run(ptimer_state *s, int oneshot)
 {
     bool was_disabled = !s->enabled;
 
-    if (was_disabled && s->period == 0) {
-        fprintf(stderr, "Timer with period zero, disabling\n");
-        return;
-    }
+    g_assert(s->period != 0);
     s->enabled = oneshot ? 2 : 1;
     if (was_disabled) {
         s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
@@ -190,6 +185,7 @@ void ptimer_stop(ptimer_state *s)
 /* Set counter increment interval in nanoseconds.  */
 void ptimer_set_period(ptimer_state *s, int64_t period)
 {
+    g_assert(period != 0);
     s->delta = ptimer_get_count(s);
     s->period = period;
     s->period_frac = 0;
@@ -202,6 +198,7 @@ void ptimer_set_period(ptimer_state *s, int64_t period)
 /* Set counter frequency in Hz.  */
 void ptimer_set_freq(ptimer_state *s, uint32_t freq)
 {
+    g_assert(freq != 0);
     s->delta = ptimer_get_count(s);
     s->period = 1000000000ll / freq;
     s->period_frac = (1000000000ll << 32) / freq;
-- 
2.7.0

[Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

Current ARM MPTimer implementation uses QEMUTimer for the actual timer,
this implementation isn't complete and mostly tries to duplicate of what
generic ptimer is already doing fine.

Conversion to ptimer brings the following benefits and fixes:
	- Simple timer pausing implementation
	- Fixes counter value preservation after stopping the timer
	- Correctly handles prescaler != 0 cases
	- Code simplification and reduction

Bump VMSD to version 3, since VMState is changed and is not compatible
with the previous implementation.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 hw/timer/arm_mptimer.c         | 131 +++++++++++++++++++++--------------------
 include/hw/timer/arm_mptimer.h |   5 +-
 2 files changed, 67 insertions(+), 69 deletions(-)

diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
index 3e59c2a..a5f46df 100644
--- a/hw/timer/arm_mptimer.c
+++ b/hw/timer/arm_mptimer.c
@@ -19,8 +19,9 @@
  * with this program; if not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "hw/ptimer.h"
 #include "hw/timer/arm_mptimer.h"
-#include "qemu/timer.h"
+#include "qemu/main-loop.h"
 #include "qom/cpu.h"
 
 /* This device implements the per-cpu private timer and watchdog block
@@ -42,33 +43,34 @@ static inline void timerblock_update_irq(TimerBlock *tb)
 }
 
 /* Return conversion factor from mpcore timer ticks to qemu timer ticks.  */
-static inline uint32_t timerblock_scale(TimerBlock *tb)
+static inline uint32_t timerblock_scale(uint32_t control)
 {
-    return (((tb->control >> 8) & 0xff) + 1) * 10;
+    return (((control >> 8) & 0xff) + 1) * 10;
 }
 
-static void timerblock_reload(TimerBlock *tb, int restart)
+static inline void timerblock_set_count(struct ptimer_state *timer,
+                                        uint32_t control, uint64_t *count)
 {
-    if (tb->count == 0) {
-        return;
+    /* PTimer would immediately trigger interrupt for periodic timer
+     * when counter set to 0, MPtimer under certain condition only.  */
+    if ((control & 3) == 3 && (*count == 0) && (control & 0xff00) == 0) {
+        *count = ptimer_get_limit(timer);
     }
-    if (restart) {
-        tb->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+    ptimer_set_count(timer, *count);
+}
+
+static inline void timerblock_run(struct ptimer_state *timer, uint32_t control,
+                                  bool cond)
+{
+    if (cond) {
+        ptimer_run(timer, !(control & 2));
     }
-    tb->tick += (int64_t)tb->count * timerblock_scale(tb);
-    timer_mod(tb->timer, tb->tick);
 }
 
 static void timerblock_tick(void *opaque)
 {
     TimerBlock *tb = (TimerBlock *)opaque;
     tb->status = 1;
-    if (tb->control & 2) {
-        tb->count = tb->load;
-        timerblock_reload(tb, 0);
-    } else {
-        tb->count = 0;
-    }
     timerblock_update_irq(tb);
 }
 
@@ -76,21 +78,11 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
                                 unsigned size)
 {
     TimerBlock *tb = (TimerBlock *)opaque;
-    int64_t val;
     switch (addr) {
     case 0: /* Load */
-        return tb->load;
+        return ptimer_get_limit(tb->timer);
     case 4: /* Counter.  */
-        if (((tb->control & 1) == 0) || (tb->count == 0)) {
-            return 0;
-        }
-        /* Slow and ugly, but hopefully won't happen too often.  */
-        val = tb->tick - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-        val /= timerblock_scale(tb);
-        if (val < 0) {
-            val = 0;
-        }
-        return val;
+        return ptimer_get_count(tb->timer);
     case 8: /* Control.  */
         return tb->control;
     case 12: /* Interrupt status.  */
@@ -104,39 +96,51 @@ static void timerblock_write(void *opaque, hwaddr addr,
                              uint64_t value, unsigned size)
 {
     TimerBlock *tb = (TimerBlock *)opaque;
-    int64_t old;
+    uint32_t control = tb->control;
     switch (addr) {
     case 0: /* Load */
-        tb->load = value;
-        /* Fall through.  */
-    case 4: /* Counter.  */
-        if ((tb->control & 1) && tb->count) {
-            /* Cancel the previous timer.  */
-            timer_del(tb->timer);
+        /* Setting load to 0 stops the timer if prescaler == 0.  */
+        if ((control & 1) && (value == 0) && (control & 0xff00) == 0) {
+            ptimer_stop(tb->timer);
+            control &= ~1;
         }
-        tb->count = value;
-        if (tb->control & 1) {
-            timerblock_reload(tb, 1);
+        ptimer_set_limit(tb->timer, value, 1);
+        timerblock_run(tb->timer, control, (control & 1));
+        break;
+    case 4: /* Counter.  */
+        /* Setting counter to 0 stops the one-shot timer if prescaler == 0
+         * and periodic if load = 0.  */
+        if ((control & 1) && (value == 0) && (control & 0xff00) == 0) {
+            if (!(control & 2) || ptimer_get_limit(tb->timer) == 0) {
+                ptimer_stop(tb->timer);
+                control &= ~1;
+            }
         }
+        timerblock_set_count(tb->timer, control, &value);
+        timerblock_run(tb->timer, control, (value != 0) && (control & 1));
         break;
     case 8: /* Control.  */
-        old = tb->control;
-        tb->control = value;
-        if (value & 1) {
-            if ((old & 1) && (tb->count != 0)) {
-                /* Do nothing if timer is ticking right now.  */
-                break;
+        if ((value & 1) && (control & 3) != (value & 3)) {
+            uint64_t count = (value & 0xff00) ? 1 : ptimer_get_count(tb->timer);
+            if ((count == 0) && (value & 2)) {
+                timerblock_set_count(tb->timer, value, &count);
             }
-            if (tb->control & 2) {
-                tb->count = tb->load;
-            }
-            timerblock_reload(tb, 1);
-        } else if (old & 1) {
-            /* Shutdown the timer.  */
-            timer_del(tb->timer);
+            timerblock_run(tb->timer, value, (count != 0));
+        } else if ((control & 1) && !(value & 1)) {
+            ptimer_stop(tb->timer);
+        }
+        if ((control & 0xff00) != (value & 0xff00)) {
+            ptimer_set_period(tb->timer, timerblock_scale(value));
         }
+        tb->control = value;
         break;
     case 12: /* Interrupt status.  */
+        /* Simulate continuous IRQ gen.  */
+        if ((control & 3) == 3 && (control & 0xff00) != 0) {
+            if (ptimer_get_limit(tb->timer) == 0) {
+                break;
+            }
+        }
         tb->status &= ~value;
         timerblock_update_irq(tb);
         break;
@@ -184,13 +188,12 @@ static const MemoryRegionOps timerblock_ops = {
 
 static void timerblock_reset(TimerBlock *tb)
 {
-    tb->count = 0;
-    tb->load = 0;
     tb->control = 0;
     tb->status = 0;
-    tb->tick = 0;
     if (tb->timer) {
-        timer_del(tb->timer);
+        ptimer_stop(tb->timer);
+        ptimer_set_limit(tb->timer, 0, 1);
+        ptimer_set_period(tb->timer, timerblock_scale(0));
     }
 }
 
@@ -235,7 +238,8 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
      */
     for (i = 0; i < s->num_cpu; i++) {
         TimerBlock *tb = &s->timerblock[i];
-        tb->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, timerblock_tick, tb);
+        QEMUBH *bh = qemu_bh_new(timerblock_tick, tb);
+        tb->timer = ptimer_init(bh);
         sysbus_init_irq(sbd, &tb->irq);
         memory_region_init_io(&tb->iomem, OBJECT(s), &timerblock_ops, tb,
                               "arm_mptimer_timerblock", 0x20);
@@ -245,26 +249,23 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
 
 static const VMStateDescription vmstate_timerblock = {
     .name = "arm_mptimer_timerblock",
-    .version_id = 2,
-    .minimum_version_id = 2,
+    .version_id = 3,
+    .minimum_version_id = 3,
     .fields = (VMStateField[]) {
-        VMSTATE_UINT32(count, TimerBlock),
-        VMSTATE_UINT32(load, TimerBlock),
         VMSTATE_UINT32(control, TimerBlock),
         VMSTATE_UINT32(status, TimerBlock),
-        VMSTATE_INT64(tick, TimerBlock),
-        VMSTATE_TIMER_PTR(timer, TimerBlock),
+        VMSTATE_PTIMER(timer, TimerBlock),
         VMSTATE_END_OF_LIST()
     }
 };
 
 static const VMStateDescription vmstate_arm_mptimer = {
     .name = "arm_mptimer",
-    .version_id = 2,
-    .minimum_version_id = 2,
+    .version_id = 3,
+    .minimum_version_id = 3,
     .fields = (VMStateField[]) {
         VMSTATE_STRUCT_VARRAY_UINT32(timerblock, ARMMPTimerState, num_cpu,
-                                     2, vmstate_timerblock, TimerBlock),
+                                     3, vmstate_timerblock, TimerBlock),
         VMSTATE_END_OF_LIST()
     }
 };
diff --git a/include/hw/timer/arm_mptimer.h b/include/hw/timer/arm_mptimer.h
index b34cba0..c46d8d2 100644
--- a/include/hw/timer/arm_mptimer.h
+++ b/include/hw/timer/arm_mptimer.h
@@ -27,12 +27,9 @@
 
 /* State of a single timer or watchdog block */
 typedef struct {
-    uint32_t count;
-    uint32_t load;
     uint32_t control;
     uint32_t status;
-    int64_t tick;
-    QEMUTimer *timer;
+    struct ptimer_state *timer;
     qemu_irq irq;
     MemoryRegion iomem;
 } TimerBlock;
-- 
2.7.0

Re: [Qemu-devel] [PATCH v11 6/7] hw/ptimer: Legalize running with delta = load = 0 and abort on period = 0

[Peter Crosthwaite]

On Thu, Jan 21, 2016 at 11:03 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> Currently ptimer would print error message and clear enable flag for an
> arming timer that has delta = load = 0. That actually could be a valid case
> for some hardware, like instant IRQ trigger for oneshot timer or continuous
> in periodic mode. Support those cases by removing the error message and
> stopping the timer when delta = 0. Abort execution when period = 0 instead
> of printing the error message, otherwise there is a chance to miss that error.
>
> In addition, don't re-load oneshot timer when delta = 0 and remove duplicated
> code from ptimer_tick(), since ptimer_reload would invoke trigger and stop
> the timer.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>

Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>

> ---
>  hw/core/ptimer.c | 27 ++++++++++++---------------
>  1 file changed, 12 insertions(+), 15 deletions(-)
>
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index 142cc64..cec59e1 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -39,11 +39,14 @@ static void ptimer_reload(ptimer_state *s)
>
>      if (s->delta == 0) {
>          ptimer_trigger(s);
> +    }
> +
> +    if (s->delta == 0 && s->enabled == 1) {
>          s->delta = s->limit;
>      }
> -    if (s->delta == 0 || s->period == 0) {
> -        fprintf(stderr, "Timer with period zero, disabling\n");
> -        s->enabled = 0;
> +
> +    if (s->delta == 0) {
> +        ptimer_stop(s);
>          return;
>      }
>
> @@ -72,27 +75,22 @@ static void ptimer_reload(ptimer_state *s)
>  static void ptimer_tick(void *opaque)
>  {
>      ptimer_state *s = (ptimer_state *)opaque;
> -    ptimer_trigger(s);
>      s->delta = 0;
> -    if (s->enabled == 2) {
> -        s->enabled = 0;
> -    } else {
> -        ptimer_reload(s);
> -    }
> +    ptimer_reload(s);
>  }
>
>  uint64_t ptimer_get_count(ptimer_state *s)
>  {
>      uint64_t counter;
>
> -    if (s->enabled) {
> +    if (s->enabled && s->delta != 0) {
>          int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
>          int64_t next = s->next_event;
>          bool expired = (now - next >= 0);
>          bool oneshot = (s->enabled == 2);
>
>          /* Figure out the current counter value.  */
> -        if (s->period == 0 || (expired && (oneshot || use_icount))) {
> +        if (expired && (oneshot || use_icount)) {
>              /* Prevent timer underflowing if it should already have
>                 triggered.  */
>              counter = 0;
> @@ -164,10 +162,7 @@ void ptimer_run(ptimer_state *s, int oneshot)
>  {
>      bool was_disabled = !s->enabled;
>
> -    if (was_disabled && s->period == 0) {
> -        fprintf(stderr, "Timer with period zero, disabling\n");
> -        return;
> -    }
> +    g_assert(s->period != 0);
>      s->enabled = oneshot ? 2 : 1;
>      if (was_disabled) {
>          s->next_event = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> @@ -190,6 +185,7 @@ void ptimer_stop(ptimer_state *s)
>  /* Set counter increment interval in nanoseconds.  */
>  void ptimer_set_period(ptimer_state *s, int64_t period)
>  {
> +    g_assert(period != 0);
>      s->delta = ptimer_get_count(s);
>      s->period = period;
>      s->period_frac = 0;
> @@ -202,6 +198,7 @@ void ptimer_set_period(ptimer_state *s, int64_t period)
>  /* Set counter frequency in Hz.  */
>  void ptimer_set_freq(ptimer_state *s, uint32_t freq)
>  {
> +    g_assert(freq != 0);
>      s->delta = ptimer_get_count(s);
>      s->period = 1000000000ll / freq;
>      s->period_frac = (1000000000ll << 32) / freq;
> --
> 2.7.0
>

Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer

[Peter Crosthwaite]

On Thu, Jan 21, 2016 at 11:03 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> Current ARM MPTimer implementation uses QEMUTimer for the actual timer,
> this implementation isn't complete and mostly tries to duplicate of what
> generic ptimer is already doing fine.
>
> Conversion to ptimer brings the following benefits and fixes:
>         - Simple timer pausing implementation
>         - Fixes counter value preservation after stopping the timer
>         - Correctly handles prescaler != 0 cases
>         - Code simplification and reduction
>
> Bump VMSD to version 3, since VMState is changed and is not compatible
> with the previous implementation.
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
>  hw/timer/arm_mptimer.c         | 131 +++++++++++++++++++++--------------------
>  include/hw/timer/arm_mptimer.h |   5 +-
>  2 files changed, 67 insertions(+), 69 deletions(-)
>
> diff --git a/hw/timer/arm_mptimer.c b/hw/timer/arm_mptimer.c
> index 3e59c2a..a5f46df 100644
> --- a/hw/timer/arm_mptimer.c
> +++ b/hw/timer/arm_mptimer.c
> @@ -19,8 +19,9 @@
>   * with this program; if not, see <http://www.gnu.org/licenses/>.
>   */
>
> +#include "hw/ptimer.h"
>  #include "hw/timer/arm_mptimer.h"
> -#include "qemu/timer.h"
> +#include "qemu/main-loop.h"
>  #include "qom/cpu.h"
>
>  /* This device implements the per-cpu private timer and watchdog block
> @@ -42,33 +43,34 @@ static inline void timerblock_update_irq(TimerBlock *tb)
>  }
>
>  /* Return conversion factor from mpcore timer ticks to qemu timer ticks.  */
> -static inline uint32_t timerblock_scale(TimerBlock *tb)
> +static inline uint32_t timerblock_scale(uint32_t control)
>  {
> -    return (((tb->control >> 8) & 0xff) + 1) * 10;
> +    return (((control >> 8) & 0xff) + 1) * 10;
>  }
>
> -static void timerblock_reload(TimerBlock *tb, int restart)
> +static inline void timerblock_set_count(struct ptimer_state *timer,
> +                                        uint32_t control, uint64_t *count)
>  {
> -    if (tb->count == 0) {
> -        return;
> +    /* PTimer would immediately trigger interrupt for periodic timer
> +     * when counter set to 0, MPtimer under certain condition only.  */

newline before */

> +    if ((control & 3) == 3 && (*count == 0) && (control & 0xff00) == 0) {
> +        *count = ptimer_get_limit(timer);
>      }
> -    if (restart) {
> -        tb->tick = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +    ptimer_set_count(timer, *count);
> +}
> +
> +static inline void timerblock_run(struct ptimer_state *timer, uint32_t control,
> +                                  bool cond)

drop cond ...

> +{
> +    if (cond) {

... control & 1 ...

> +        ptimer_run(timer, !(control & 2));
>      }
> -    tb->tick += (int64_t)tb->count * timerblock_scale(tb);
> -    timer_mod(tb->timer, tb->tick);
>  }
>
>  static void timerblock_tick(void *opaque)
>  {
>      TimerBlock *tb = (TimerBlock *)opaque;
>      tb->status = 1;
> -    if (tb->control & 2) {
> -        tb->count = tb->load;
> -        timerblock_reload(tb, 0);
> -    } else {
> -        tb->count = 0;
> -    }
>      timerblock_update_irq(tb);
>  }
>
> @@ -76,21 +78,11 @@ static uint64_t timerblock_read(void *opaque, hwaddr addr,
>                                  unsigned size)
>  {
>      TimerBlock *tb = (TimerBlock *)opaque;
> -    int64_t val;
>      switch (addr) {
>      case 0: /* Load */
> -        return tb->load;
> +        return ptimer_get_limit(tb->timer);
>      case 4: /* Counter.  */
> -        if (((tb->control & 1) == 0) || (tb->count == 0)) {
> -            return 0;
> -        }
> -        /* Slow and ugly, but hopefully won't happen too often.  */
> -        val = tb->tick - qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> -        val /= timerblock_scale(tb);
> -        if (val < 0) {
> -            val = 0;
> -        }
> -        return val;
> +        return ptimer_get_count(tb->timer);
>      case 8: /* Control.  */
>          return tb->control;
>      case 12: /* Interrupt status.  */
> @@ -104,39 +96,51 @@ static void timerblock_write(void *opaque, hwaddr addr,
>                               uint64_t value, unsigned size)
>  {
>      TimerBlock *tb = (TimerBlock *)opaque;
> -    int64_t old;
> +    uint32_t control = tb->control;
>      switch (addr) {
>      case 0: /* Load */
> -        tb->load = value;
> -        /* Fall through.  */
> -    case 4: /* Counter.  */
> -        if ((tb->control & 1) && tb->count) {
> -            /* Cancel the previous timer.  */
> -            timer_del(tb->timer);
> +        /* Setting load to 0 stops the timer if prescaler == 0.  */
> +        if ((control & 1) && (value == 0) && (control & 0xff00) == 0) {
> +            ptimer_stop(tb->timer);
> +            control &= ~1;
>          }
> -        tb->count = value;
> -        if (tb->control & 1) {
> -            timerblock_reload(tb, 1);
> +        ptimer_set_limit(tb->timer, value, 1);
> +        timerblock_run(tb->timer, control, (control & 1));
> +        break;
> +    case 4: /* Counter.  */
> +        /* Setting counter to 0 stops the one-shot timer if prescaler == 0
> +         * and periodic if load = 0.  */

newline before */

> +        if ((control & 1) && (value == 0) && (control & 0xff00) == 0) {
> +            if (!(control & 2) || ptimer_get_limit(tb->timer) == 0) {

comment doesn't look to match code. The code looks like:

"setting counter to 0 while prescaler == 0 will disable the timer if
it is either oneshot, or periodic with load == 0",

whearas your comment read as if it only applies to one-shot timers.

ifs can be merged.

> +                ptimer_stop(tb->timer);
> +                control &= ~1;
> +            }
>          }
> +        timerblock_set_count(tb->timer, control, &value);

... and just add in the extra if in here with if (value != 0). The
boolean cond argument that just conditionalizes the whole thing is a
bit un-usual and the three call sites all pass in (control & 1) in
addition to the full raw control.

> +        timerblock_run(tb->timer, control, (value != 0) && (control & 1));
>          break;
>      case 8: /* Control.  */
> -        old = tb->control;
> -        tb->control = value;
> -        if (value & 1) {
> -            if ((old & 1) && (tb->count != 0)) {
> -                /* Do nothing if timer is ticking right now.  */
> -                break;
> +        if ((value & 1) && (control & 3) != (value & 3)) {
> +            uint64_t count = (value & 0xff00) ? 1 : ptimer_get_count(tb->timer);
> +            if ((count == 0) && (value & 2)) {
> +                timerblock_set_count(tb->timer, value, &count);

This looks like a weird corner-case, what does it do exactly? I can't
follow it so it needs a comment :)

Regards,
Peter

>              }
> -            if (tb->control & 2) {
> -                tb->count = tb->load;
> -            }
> -            timerblock_reload(tb, 1);
> -        } else if (old & 1) {
> -            /* Shutdown the timer.  */
> -            timer_del(tb->timer);
> +            timerblock_run(tb->timer, value, (count != 0));
> +        } else if ((control & 1) && !(value & 1)) {
> +            ptimer_stop(tb->timer);
> +        }
> +        if ((control & 0xff00) != (value & 0xff00)) {
> +            ptimer_set_period(tb->timer, timerblock_scale(value));
>          }
> +        tb->control = value;
>          break;
>      case 12: /* Interrupt status.  */
> +        /* Simulate continuous IRQ gen.  */
> +        if ((control & 3) == 3 && (control & 0xff00) != 0) {
> +            if (ptimer_get_limit(tb->timer) == 0) {
> +                break;
> +            }
> +        }
>          tb->status &= ~value;
>          timerblock_update_irq(tb);
>          break;
> @@ -184,13 +188,12 @@ static const MemoryRegionOps timerblock_ops = {
>
>  static void timerblock_reset(TimerBlock *tb)
>  {
> -    tb->count = 0;
> -    tb->load = 0;
>      tb->control = 0;
>      tb->status = 0;
> -    tb->tick = 0;
>      if (tb->timer) {
> -        timer_del(tb->timer);
> +        ptimer_stop(tb->timer);
> +        ptimer_set_limit(tb->timer, 0, 1);
> +        ptimer_set_period(tb->timer, timerblock_scale(0));
>      }
>  }
>
> @@ -235,7 +238,8 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
>       */
>      for (i = 0; i < s->num_cpu; i++) {
>          TimerBlock *tb = &s->timerblock[i];
> -        tb->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, timerblock_tick, tb);
> +        QEMUBH *bh = qemu_bh_new(timerblock_tick, tb);
> +        tb->timer = ptimer_init(bh);
>          sysbus_init_irq(sbd, &tb->irq);
>          memory_region_init_io(&tb->iomem, OBJECT(s), &timerblock_ops, tb,
>                                "arm_mptimer_timerblock", 0x20);
> @@ -245,26 +249,23 @@ static void arm_mptimer_realize(DeviceState *dev, Error **errp)
>
>  static const VMStateDescription vmstate_timerblock = {
>      .name = "arm_mptimer_timerblock",
> -    .version_id = 2,
> -    .minimum_version_id = 2,
> +    .version_id = 3,
> +    .minimum_version_id = 3,
>      .fields = (VMStateField[]) {
> -        VMSTATE_UINT32(count, TimerBlock),
> -        VMSTATE_UINT32(load, TimerBlock),
>          VMSTATE_UINT32(control, TimerBlock),
>          VMSTATE_UINT32(status, TimerBlock),
> -        VMSTATE_INT64(tick, TimerBlock),
> -        VMSTATE_TIMER_PTR(timer, TimerBlock),
> +        VMSTATE_PTIMER(timer, TimerBlock),
>          VMSTATE_END_OF_LIST()
>      }
>  };
>
>  static const VMStateDescription vmstate_arm_mptimer = {
>      .name = "arm_mptimer",
> -    .version_id = 2,
> -    .minimum_version_id = 2,
> +    .version_id = 3,
> +    .minimum_version_id = 3,
>      .fields = (VMStateField[]) {
>          VMSTATE_STRUCT_VARRAY_UINT32(timerblock, ARMMPTimerState, num_cpu,
> -                                     2, vmstate_timerblock, TimerBlock),
> +                                     3, vmstate_timerblock, TimerBlock),
>          VMSTATE_END_OF_LIST()
>      }
>  };
> diff --git a/include/hw/timer/arm_mptimer.h b/include/hw/timer/arm_mptimer.h
> index b34cba0..c46d8d2 100644
> --- a/include/hw/timer/arm_mptimer.h
> +++ b/include/hw/timer/arm_mptimer.h
> @@ -27,12 +27,9 @@
>
>  /* State of a single timer or watchdog block */
>  typedef struct {
> -    uint32_t count;
> -    uint32_t load;
>      uint32_t control;
>      uint32_t status;
> -    int64_t tick;
> -    QEMUTimer *timer;
> +    struct ptimer_state *timer;
>      qemu_irq irq;
>      MemoryRegion iomem;
>  } TimerBlock;
> --
> 2.7.0
>

Re: [Qemu-devel] [PATCH v11 2/7] hw/ptimer: Perform counter wrap around if timer already expired

[Peter Crosthwaite]

On Thu, Jan 21, 2016 at 11:03 AM, Dmitry Osipenko <digetx@gmail.com> wrote:
> ptimer_get_count() might be called while QEMU timer already been expired.
> In that case ptimer would return counter = 0, which might be undesirable
> in case of polled timer. Do counter wrap around for periodic timer to keep
> it distributed. In order to achieve more accurate emulation behaviour of
> certain hardware, don't perform wrap around when in icount mode and return
> counter = 0 in that case (that doesn't affect polled counter distribution).
>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>

Reviewed-by: Peter Crosthwaite <crosthwaite.peter@gmail.com>

> ---
>  hw/core/ptimer.c | 19 +++++++++++++------
>  1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c
> index 6dc1677..cb50d30 100644
> --- a/hw/core/ptimer.c
> +++ b/hw/core/ptimer.c
> @@ -83,14 +83,16 @@ static void ptimer_tick(void *opaque)
>
>  uint64_t ptimer_get_count(ptimer_state *s)
>  {
> -    int64_t now;
>      uint64_t counter;
>
>      if (s->enabled) {
> -        now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +        int64_t now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
> +        int64_t next = s->next_event;
> +        bool expired = (now - next >= 0);
> +        bool oneshot = (s->enabled == 2);
> +
>          /* Figure out the current counter value.  */
> -        if (now - s->next_event > 0
> -            || s->period == 0) {
> +        if (s->period == 0 || (expired && (oneshot || use_icount))) {
>              /* Prevent timer underflowing if it should already have
>                 triggered.  */
>              counter = 0;
> @@ -102,7 +104,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
>              uint32_t period_frac = s->period_frac;
>              uint64_t period = s->period;
>
> -            if ((s->enabled == 1) && !use_icount && (s->delta * period < 10000)) {
> +            if (!oneshot && (s->delta * period < 10000) && !use_icount) {
>                  period = 10000 / s->delta;
>                  period_frac = 0;
>              }
> @@ -117,7 +119,7 @@ uint64_t ptimer_get_count(ptimer_state *s)
>                 backwards.
>              */
>
> -            rem = s->next_event - now;
> +            rem = expired ? now - next : next - now;
>              div = period;
>
>              clz1 = clz64(rem);
> @@ -137,6 +139,11 @@ uint64_t ptimer_get_count(ptimer_state *s)
>                      div += 1;
>              }
>              counter = rem / div;
> +
> +            if (expired && (counter != 0)) {
> +                /* Wrap around periodic counter.  */
> +                counter = s->limit - counter % s->limit;
> +            }
>          }
>      } else {
>          counter = s->delta;
> --
> 2.7.0
>

Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

Hello Peter,

24.01.2016 08:25, Peter Crosthwaite пишет:

[snip]

>> +        timerblock_run(tb->timer, control, (value != 0) && (control & 1));
>>           break;
>>       case 8: /* Control.  */
>> -        old = tb->control;
>> -        tb->control = value;
>> -        if (value & 1) {
>> -            if ((old & 1) && (tb->count != 0)) {
>> -                /* Do nothing if timer is ticking right now.  */
>> -                break;
>> +        if ((value & 1) && (control & 3) != (value & 3)) {
>> +            uint64_t count = (value & 0xff00) ? 1 : ptimer_get_count(tb->timer);
>> +            if ((count == 0) && (value & 2)) {
>> +                timerblock_set_count(tb->timer, value, &count);
>
> This looks like a weird corner-case, what does it do exactly? I can't
> follow it so it needs a comment :)
>

It does the following:

mode     | prescaler | reload if counter == 0 | tick immediately if counter == 0
--------------------------------------------------------------------------------
oneshot	     == 0               0                         0
oneshot      != 0               0                         1
periodic     == 0               1                         0
periodic     != 0               0                         1

If writing control register with prescaler = 0, then for one-shot timer with 
counter == 0 or periodic timer with load = counter == 0 this is NOP. Will add a 
comment.

Thanks for review!

-- 
Dmitry

Re: [Qemu-devel] [PATCH v11 6/7] hw/ptimer: Legalize running with delta = load = 0 and abort on period = 0

[Dmitry Osipenko]

24.01.2016 07:28, Peter Crosthwaite пишет:

[snip]

>>   /* Set counter frequency in Hz.  */
>>   void ptimer_set_freq(ptimer_state *s, uint32_t freq)
>>   {
>> +    g_assert(freq != 0);
>>       s->delta = ptimer_get_count(s);
>>       s->period = 1000000000ll / freq;
>>       s->period_frac = (1000000000ll << 32) / freq;

I noticed that this should be g_assert(freq != 0 && freq <= 1000000000), 
otherwise it possible to make period = 0 for the running timer when setting freq 
 > 1GHz, which doesn't make sense because we can't set period < 1ns.

Or maybe we should clamp period = max(1, period), freq = min(1000000000, freq) 
to "allow" higher timer freq's?

What do you think?

-- 
Dmitry

Re: [Qemu-devel] [PATCH v11 2/7] hw/ptimer: Perform counter wrap around if timer already expired

[Dmitry Osipenko]

Hello Peter,

24.01.2016 08:29, Peter Crosthwaite пишет:

[snip]

>> +            if (expired && (counter != 0)) {
>> +                /* Wrap around periodic counter.  */
>> +                counter = s->limit - counter % s->limit;
>> +            }

Noticed another nit here. This should be:

counter = s->limit - (counter - 1) % s->limit;

So wraparound for counter = -1 is counter = limit (not limit - 1). Will fix it 
in V12.

I suppose your r-b is still valid, otherwise please let me know.

-- 
Dmitry

Re: [Qemu-devel] [PATCH v11 7/7] arm_mptimer: Convert to use ptimer

[Dmitry Osipenko]

24.01.2016 17:59, Dmitry Osipenko пишет:
> Hello Peter,
>
> 24.01.2016 08:25, Peter Crosthwaite пишет:
>
> [snip]
>
>>> +        timerblock_run(tb->timer, control, (value != 0) && (control & 1));
>>>           break;
>>>       case 8: /* Control.  */
>>> -        old = tb->control;
>>> -        tb->control = value;
>>> -        if (value & 1) {
>>> -            if ((old & 1) && (tb->count != 0)) {
>>> -                /* Do nothing if timer is ticking right now.  */
>>> -                break;
>>> +        if ((value & 1) && (control & 3) != (value & 3)) {
>>> +            uint64_t count = (value & 0xff00) ? 1 :
>>> ptimer_get_count(tb->timer);
>>> +            if ((count == 0) && (value & 2)) {
>>> +                timerblock_set_count(tb->timer, value, &count);
>>
>> This looks like a weird corner-case, what does it do exactly? I can't
>> follow it so it needs a comment :)
>>
>
> It does the following:
>
> mode     | prescaler | reload if counter == 0 | tick immediately if counter == 0
> --------------------------------------------------------------------------------
> oneshot         == 0               0                         0
> oneshot      != 0               0                         1
> periodic     == 0               1                         0
> periodic     != 0               0                         1
>
> If writing control register with prescaler = 0, then for one-shot timer with
> counter == 0 or periodic timer with load = counter == 0 this is NOP. Will add a
> comment.
>
> Thanks for review!
>

Just realized that I missed timer re-run on prescaler change. So it was a good 
question! =)

-- 
Dmitry