From a77be3c28270ede4ea7daac86b40aca933ea1f8b Mon Sep 17 00:00:00 2001
From: Alex Zenla <alex@edera.dev>
Date: Thu, 30 Oct 2025 02:51:52 -0400
Subject: [PATCH] feat(bootloader-interface): measure time in firmware as well

---
 src/integrations/bootloader_interface.rs | 16 +++++++++++-----
 src/main.rs                              |  2 +-
 src/platform.rs                          |  2 +-
 src/platform/timer.rs                    |  7 ++++++-
 4 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/src/integrations/bootloader_interface.rs b/src/integrations/bootloader_interface.rs
index b291d70..0e6cf91 100644
--- a/src/integrations/bootloader_interface.rs
+++ b/src/integrations/bootloader_interface.rs
@@ -11,15 +11,21 @@ impl BootloaderInterface {
     const VENDOR: VariableVendor = VariableVendor(guid!("4a67b082-0a4c-41cf-b6c7-440b29bb8c4f"));
 
     /// Tell the system that Sprout was initialized at the current time.
-    pub fn mark_init() -> Result<()> {
-        Self::set_cstr16("LoaderTimeInitUSec", "0")
+    pub fn mark_init(timer: &PlatformTimer) -> Result<()> {
+        Self::mark_time("LoaderTimeInitUSec", timer)
     }
 
     /// Tell the system that Sprout is about to execute the boot entry.
     pub fn mark_exec(timer: &PlatformTimer) -> Result<()> {
-        // Measure the elapsed time since the bootloader was started.
-        let elapsed = timer.elapsed();
-        Self::set_cstr16("LoaderTimeExecUSec", &elapsed.as_micros().to_string())
+        Self::mark_time("LoaderTimeExecUSec", timer)
+    }
+
+    /// Tell the system about the current time as measured by the platform timer.
+    /// Sets the variable specified by `key` to the number of microseconds.
+    fn mark_time(key: &str, timer: &PlatformTimer) -> Result<()> {
+        // Measure the elapsed time since the hardware timer was started.
+        let elapsed = timer.elapsed_since_lifetime();
+        Self::set_cstr16(key, &elapsed.as_micros().to_string())
     }
 
     /// Tell the system what the partition GUID of the ESP Sprout was booted from is.
diff --git a/src/main.rs b/src/main.rs
index 7a62242..8385dd5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -69,7 +69,7 @@ fn run() -> Result<()> {
     let timer = PlatformTimer::start();
 
     // Mark the initialization of Sprout in the bootloader interface.
-    BootloaderInterface::mark_init()
+    BootloaderInterface::mark_init(&timer)
         .context("unable to mark initialization in bootloader interface")?;
 
     // Parse the options to the sprout executable.
diff --git a/src/platform.rs b/src/platform.rs
index 25b5b1f..66d17b4 100644
--- a/src/platform.rs
+++ b/src/platform.rs
@@ -1,2 +1,2 @@
-/// timer: Platform timer support code.
+/// timer: Platform timer support.
 pub mod timer;
diff --git a/src/platform/timer.rs b/src/platform/timer.rs
index 80e151a..9a2d9be 100644
--- a/src/platform/timer.rs
+++ b/src/platform/timer.rs
@@ -73,8 +73,13 @@ impl PlatformTimer {
         }
     }
 
+    /// Measure the elapsed duration since the hardware started ticking upwards.
+    pub fn elapsed_since_lifetime(&self) -> Duration {
+        self.frequency.duration(arch_ticks())
+    }
+
     /// Measure the elapsed duration since the timer was started.
-    pub fn elapsed(&self) -> Duration {
+    pub fn elapsed_since_start(&self) -> Duration {
         let duration = arch_ticks() - self.start;
         self.frequency.duration(duration)
     }