runtime: Halt the cpu between mailbox commands

Use interrupts to wake the CPU from a halted state to deal with mailbox commands. Signed-off-by: Arthur Heymans <[email protected]>
korran · Feb 5, 2024 · 3d3c5b1 · 3d3c5b1
1 parent c77993a
commit 3d3c5b1
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Showing 3 changed files with 55 additions and 16 deletions.
diff --git a/runtime/src/drivers.rs b/runtime/src/drivers.rs
@@ -27,12 +27,13 @@ use arrayvec::ArrayVec;
 use caliptra_drivers::KeyId;
 use caliptra_drivers::{
     cprint, cprintln, pcr_log::RT_FW_JOURNEY_PCR, Array4x12, CaliptraError, CaliptraResult,
-    DataVault, Ecc384, KeyVault, Lms, PersistentDataAccessor, ResetReason, Sha1, SocIfc,
+    DataVault, Ecc384, KeyVault, Lms, PersistentDataAccessor, Pic, ResetReason, Sha1, SocIfc,
 };
 use caliptra_drivers::{
     hand_off::DataStore, Ecc384PubKey, Hmac384, PcrBank, PcrId, Sha256, Sha256Alg, Sha384,
     Sha384Acc, Trng,
 };
+use caliptra_registers::el2_pic_ctrl::El2PicCtrl;
 use caliptra_registers::mbox::enums::MboxStatusE;
 use caliptra_registers::{
     csrng::CsrngReg, dv::DvReg, ecc::EccReg, entropy_src::EntropySrcReg, hmac::HmacReg, kv::KvReg,
@@ -86,6 +87,8 @@ pub struct Drivers {
 
     pub pcr_bank: PcrBank,
 
+    pub pic: Pic,
+
     pub cert_chain: ArrayVec<u8, MAX_CERT_CHAIN_SIZE>,
 
     #[cfg(feature = "fips_self_test")]
@@ -157,6 +160,7 @@ impl Drivers {
             trng,
             persistent_data: PersistentDataAccessor::new(),
             pcr_bank: PcrBank::new(PvReg::new()),
+            pic: Pic::new(El2PicCtrl::new()),
             #[cfg(feature = "fips_self_test")]
             self_test_status: SelfTestStatus::Idle,
             cert_chain: ArrayVec::new(),

diff --git a/runtime/src/lib.rs b/runtime/src/lib.rs
@@ -59,7 +59,8 @@ use tagging::{GetTaggedTciCmd, TagTciCmd};
 use caliptra_common::cprintln;
 
 use caliptra_drivers::{CaliptraError, CaliptraResult, ResetReason};
-use caliptra_registers::mbox::enums::MboxStatusE;
+use caliptra_registers::el2_pic_ctrl::El2PicCtrl;
+use caliptra_registers::{mbox::enums::MboxStatusE, soc_ifc};
 use dpe::{
     commands::{CommandExecution, DeriveContextCmd, DeriveContextFlags},
     dpe_instance::{DpeEnv, DpeTypes},
@@ -118,14 +119,17 @@ fn enter_idle(drivers: &mut Drivers) {
                 Ok(_) => drivers.self_test_status = SelfTestStatus::Done,
                 Err(e) => caliptra_drivers::report_fw_error_non_fatal(e.into()),
             }
+        } else {
+            // Don't enter low power mode when in progress
+            return;
         }
     }
 
-    // TODO: Enable interrupts?
-    //#[cfg(feature = "riscv")]
-    //unsafe {
-    //core::arch::asm!("wfi");
-    //}
+    #[cfg(feature = "riscv")]
+    if cfg!(feature = "fpga_realtime") {
+        // TODO implement in emulator
+        caliptra_cpu::csr::mpmc_halt();
+    }
 }
 
 /// Handles the pending mailbox command and writes the repsonse back to the mailbox
@@ -205,6 +209,20 @@ fn handle_command(drivers: &mut Drivers) -> CaliptraResult<MboxStatusE> {
     Ok(MboxStatusE::DataReady)
 }
 
+#[cfg(feature = "riscv")]
+// TODO implement in emulator
+fn setup_mailbox_wfi(drivers: &mut Drivers) {
+    use caliptra_drivers::IntSource;
+
+    caliptra_cpu::csr::mie_enable_external_interrupts();
+
+    // Set highest priority so that Int can wake CPU
+    drivers.pic.int_set_max_priority(IntSource::SocIfcNotif);
+    drivers.pic.int_enable(IntSource::SocIfcNotif);
+
+    drivers.soc_ifc.enable_mbox_notif_interrupts();
+}
+
 /// Handles mailbox commands when the command is ready
 pub fn handle_mailbox_commands(drivers: &mut Drivers) -> CaliptraResult<()> {
     // Indicator to SOC that RT firmware is ready
@@ -229,6 +247,11 @@ pub fn handle_mailbox_commands(drivers: &mut Drivers) -> CaliptraResult<()> {
             }
         }
     }
+    #[cfg(feature = "riscv")]
+    if cfg!(feature = "fpga_realtime") {
+        setup_mailbox_wfi(drivers);
+    }
+
     loop {
         enter_idle(drivers);
         if drivers.is_shutdown {

diff --git a/runtime/src/main.rs b/runtime/src/main.rs
@@ -79,21 +79,33 @@ extern "C" fn exception_handler(trap_record: &TrapRecord) {
     handle_fatal_error(caliptra_drivers::CaliptraError::RUNTIME_GLOBAL_EXCEPTION.into());
 }
 
+const NON_DCCM_NMI: u32 = 0xF000_1002;
+
 #[no_mangle]
 #[inline(never)]
 #[allow(clippy::empty_loop)]
 extern "C" fn nmi_handler(trap_record: &TrapRecord) {
-    let soc_ifc = unsafe { SocIfcReg::new() };
+    let mut soc_ifc = unsafe { SocIfcReg::new() };
+
+    let soc_ifc_regs = soc_ifc.regs_mut();
+    let intr_block = soc_ifc_regs.intr_block_rf();
+
+    // TODO implement MMIO reg for emulator
+    if cfg!(feature = "fpga_realtime") {
+        let notif_interrupt_status = intr_block.notif_internal_intr_r();
+
+        // On wake from mailbox command, clear the interrupt status and mret to continue execution
+        if notif_interrupt_status.read().notif_cmd_avail_sts() && trap_record.mcause == NON_DCCM_NMI
+        // Machine Fast Interrupt non-DCCM region NMI
+        {
+            notif_interrupt_status.modify(|w| w.notif_cmd_avail_sts(true));
+            return;
+        }
+    }
 
     // If the NMI was fired by caliptra instead of the uC, this register
     // contains the reason(s)
-    let err_interrupt_status = u32::from(
-        soc_ifc
-            .regs()
-            .intr_block_rf()
-            .error_internal_intr_r()
-            .read(),
-    );
+    let err_interrupt_status = u32::from(intr_block.error_internal_intr_r().read());
     log_trap_record(trap_record, Some(err_interrupt_status));
     cprintln!(
         "RT NMI mcause=0x{:08X} mscause=0x{:08X} mepc=0x{:08X} ra=0x{:08X} error_internal_intr_r={:08X}",
@@ -104,7 +116,7 @@ extern "C" fn nmi_handler(trap_record: &TrapRecord) {
         err_interrupt_status,
     );
 
-    let wdt_status = soc_ifc.regs().cptra_wdt_status().read();
+    let wdt_status = soc_ifc_regs.cptra_wdt_status().read();
     let error = if wdt_status.t1_timeout() || wdt_status.t2_timeout() {
         cprintln!("[rt] WDT Expired");
         CaliptraError::RUNTIME_GLOBAL_WDT_EXPIRED