Kernel: Fix issues supporting HPETs with 32-bit-only main counter

If the HPET main counter does not support full 64 bits, we should
not expect the upper 32 bit to work. This is a problem when writing
to the upper 32 bit of the comparator value, which requires the
TimerConfiguration::ValueSet bit to be set, but if it's not 64 bit
capable then the bit will not be cleared and leave it in a bad state.

Fixes #6990

Kernel/Time/HPET.cpp

@@ -179,7 +179,8 @@ void HPET::update_periodic_comparator_value()
     m_main_counter_drift += previous_main_value - m_main_counter_last_read;
     m_main_counter_last_read = 0;
     regs.main_counter_value.low = 0;
-    regs.main_counter_value.high = 0;
+    if (m_main_counter_64bits)
+        regs.main_counter_value.high = 0;
     for (auto& comparator : m_comparators) {
         auto& timer = regs.timers[comparator.comparator_number()];
         if (!comparator.is_enabled())
@@ -195,8 +196,10 @@ void HPET::update_periodic_comparator_value()
                 value,
                 previous_main_value);
             timer.comparator_value.low = (u32)value;
-            timer.capabilities = timer.capabilities | (u32)HPETFlags::TimerConfiguration::ValueSet;
+            if (comparator.is_64bit_capable()) {
-            timer.comparator_value.high = (u32)(value >> 32);
+                timer.capabilities = timer.capabilities | (u32)HPETFlags::TimerConfiguration::ValueSet;
+                timer.comparator_value.high = (u32)(value >> 32);
+            }
         } else {
             // Set the new target comparator value to the delta to the remaining ticks
             u64 current_value = (u64)timer.comparator_value.low | ((u64)timer.comparator_value.high << 32);
@@ -207,7 +210,8 @@ void HPET::update_periodic_comparator_value()
                 value,
                 previous_main_value);
             timer.comparator_value.low = (u32)value;
-            timer.comparator_value.high = (u32)(value >> 32);
+            if (comparator.is_64bit_capable())
+                timer.comparator_value.high = (u32)(value >> 32);
         }
     }
 
@@ -233,10 +237,14 @@ u64 HPET::update_time(u64& seconds_since_boot, u32& ticks_this_second, bool quer
     // Should only be called by the time keeper interrupt handler!
     u64 current_value = read_main_counter();
     u64 delta_ticks = m_main_counter_drift;
-    if (current_value >= m_main_counter_last_read)
+    if (current_value >= m_main_counter_last_read) {
         delta_ticks += current_value - m_main_counter_last_read;
-    else
+    } else {
-        delta_ticks += m_main_counter_last_read - current_value; // the counter wrapped around
+        // the counter wrapped around
+        delta_ticks += m_main_counter_last_read - current_value;
+        if (!m_main_counter_64bits)
+            m_32bit_main_counter_wraps++;
+    }
     u64 ticks_since_last_second = (u64)ticks_this_second + delta_ticks;
     auto ticks_per_second = frequency();
     if (ticks_since_last_second >= ticks_per_second) {
@@ -258,12 +266,24 @@ u64 HPET::update_time(u64& seconds_since_boot, u32& ticks_this_second, bool quer
 u64 HPET::read_main_counter_unsafe() const
 {
     auto& main_counter = registers().main_counter_value;
-    return ((u64)main_counter.high << 32) | (u64)main_counter.low;
+    if (m_main_counter_64bits)
+        return ((u64)main_counter.high << 32) | (u64)main_counter.low;
+
+    return ((u64)m_32bit_main_counter_wraps << 32) | (u64)main_counter.low;
 }
 
 u64 HPET::read_main_counter() const
 {
-    return read_register_safe64(registers().main_counter_value);
+    if (m_main_counter_64bits)
+        return read_register_safe64(registers().main_counter_value);
+
+    auto& main_counter = registers().main_counter_value;
+    u32 wraps = m_32bit_main_counter_wraps;
+    u32 last_read_value = m_main_counter_last_read & 0xffffffff;
+    u32 current_value = main_counter.low;
+    if (current_value < last_read_value)
+        wraps++;
+    return ((u64)wraps << 32) | (u64)current_value;
 }
 
 void HPET::enable_periodic_interrupt(const HPETComparator& comparator)
@@ -348,6 +368,13 @@ bool HPET::is_periodic_capable(u8 comparator_number) const
     return comparator_registers.capabilities & (u32)HPETFlags::TimerConfiguration::PeriodicInterruptCapable;
 }
 
+bool HPET::is_64bit_capable(u8 comparator_number) const
+{
+    VERIFY(comparator_number <= m_comparators.size());
+    auto& comparator_registers = registers().timers[comparator_number];
+    return comparator_registers.capabilities & (u32)HPETFlags::TimerConfiguration::Timer64BitsCapable;
+}
+
 void HPET::set_comparators_to_optimal_interrupt_state(size_t)
 {
     // FIXME: Implement this method for allowing to use HPET timers 2-31...
@@ -398,8 +425,9 @@ UNMAP_AFTER_INIT HPET::HPET(PhysicalAddress acpi_hpet)
 
     // Note: We must do a 32 bit access to offsets 0x0, or 0x4 only.
     size_t timers_count = ((regs.capabilities.attributes >> 8) & 0x1f) + 1;
+    m_main_counter_64bits = (regs.capabilities.attributes & (u32)HPETFlags::Attributes::Counter64BitCapable) != 0;
     dmesgln("HPET: Timers count - {}", timers_count);
-    dmesgln("HPET: Main counter size: {}", ((regs.capabilities.attributes & (u32)HPETFlags::Attributes::Counter64BitCapable) ? "64-bit" : "32-bit"));
+    dmesgln("HPET: Main counter size: {}", (m_main_counter_64bits ? "64-bit" : "32-bit"));
     for (size_t i = 0; i < timers_count; i++) {
         bool capable_64_bit = regs.timers[i].capabilities & (u32)HPETFlags::TimerConfiguration::Timer64BitsCapable;
         dmesgln("HPET: Timer[{}] comparator size: {}, mode: {}", i,
@@ -421,8 +449,8 @@ UNMAP_AFTER_INIT HPET::HPET(PhysicalAddress acpi_hpet)
     if (regs.capabilities.attributes & (u32)HPETFlags::Attributes::LegacyReplacementRouteCapable)
         regs.configuration.low = regs.configuration.low | (u32)HPETFlags::Configuration::LegacyReplacementRoute;
 
-    m_comparators.append(HPETComparator::create(0, 0, is_periodic_capable(0)));
+    m_comparators.append(HPETComparator::create(0, 0, is_periodic_capable(0), is_64bit_capable(0)));
-    m_comparators.append(HPETComparator::create(1, 8, is_periodic_capable(1)));
+    m_comparators.append(HPETComparator::create(1, 8, is_periodic_capable(1), is_64bit_capable(1)));
 
     global_enable();
 }

Kernel/Time/HPET.h

@@ -56,6 +56,7 @@ private:
     void global_enable();
 
     bool is_periodic_capable(u8 comparator_number) const;
+    bool is_64bit_capable(u8 comparator_number) const;
     void set_comparators_to_optimal_interrupt_state(size_t timers_count);
 
     u64 nanoseconds_to_raw_ticks() const;
@@ -68,12 +69,13 @@ private:
 
     u64 m_main_counter_last_read { 0 };
     u64 m_main_counter_drift { 0 };
+    u32 m_32bit_main_counter_wraps { 0 };
 
     u16 m_vendor_id;
     u16 m_minimum_tick;
     u64 m_frequency;
     u8 m_revision_id;
-    bool counter_is_64_bit_capable : 1;
+    bool m_main_counter_64bits : 1;
     bool legacy_replacement_route_capable : 1;
 
     NonnullRefPtrVector<HPETComparator> m_comparators;

Kernel/Time/HPETComparator.cpp

@@ -11,18 +11,19 @@
 
 namespace Kernel {
 
-UNMAP_AFTER_INIT NonnullRefPtr<HPETComparator> HPETComparator::create(u8 number, u8 irq, bool periodic_capable)
+UNMAP_AFTER_INIT NonnullRefPtr<HPETComparator> HPETComparator::create(u8 number, u8 irq, bool periodic_capable, bool is_64bit_capable)
 {
-    auto timer = adopt_ref(*new HPETComparator(number, irq, periodic_capable));
+    auto timer = adopt_ref(*new HPETComparator(number, irq, periodic_capable, is_64bit_capable));
     timer->register_interrupt_handler();
     return timer;
 }
 
-UNMAP_AFTER_INIT HPETComparator::HPETComparator(u8 number, u8 irq, bool periodic_capable)
+UNMAP_AFTER_INIT HPETComparator::HPETComparator(u8 number, u8 irq, bool periodic_capable, bool is_64bit_capable)
     : HardwareTimer(irq)
     , m_periodic(false)
     , m_periodic_capable(periodic_capable)
     , m_enabled(false)
+    , m_is_64bit_capable(is_64bit_capable)
     , m_comparator_number(number)
 {
 }

Kernel/Time/HPETComparator.h

@@ -16,13 +16,14 @@ class HPETComparator final : public HardwareTimer<IRQHandler> {
     friend class HPET;
 
 public:
-    static NonnullRefPtr<HPETComparator> create(u8 number, u8 irq, bool periodic_capable);
+    static NonnullRefPtr<HPETComparator> create(u8 number, u8 irq, bool periodic_capable, bool is_64bit_capable);
 
     virtual HardwareTimerType timer_type() const override { return HardwareTimerType::HighPrecisionEventTimer; }
     virtual const char* model() const override { return "HPET"; }
 
     u8 comparator_number() const { return m_comparator_number; }
     bool is_enabled() const { return m_enabled; }
+    bool is_64bit_capable() const { return m_is_64bit_capable; }
 
     virtual size_t ticks_per_second() const override;
 
@@ -43,10 +44,11 @@ public:
 private:
     void set_new_countdown();
     virtual void handle_irq(const RegisterState&) override;
-    HPETComparator(u8 number, u8 irq, bool periodic_capable);
+    HPETComparator(u8 number, u8 irq, bool periodic_capable, bool is_64bit_capable);
     bool m_periodic : 1;
     bool m_periodic_capable : 1;
     bool m_enabled : 1;
+    bool m_is_64bit_capable : 1;
     u8 m_comparator_number { 0 };
 };
 }