From ec25ee86014d021d0838e8c8addf41bf1d604d46 Mon Sep 17 00:00:00 2001
From: sawyer bristol <sawyerbristol@gmail.com>
Date: Thu, 4 Sep 2025 18:33:43 -0600
Subject: [PATCH] fix framebuffer crash

---
 kernel/src/abi.rs     | 22 ++++++++++++++--------
 kernel/src/display.rs | 30 +++++++++++++-----------------
 kernel/src/main.rs    |  3 +--
 kernel/src/ui.rs      | 19 ++++++-------------
 4 files changed, 34 insertions(+), 40 deletions(-)

diff --git a/kernel/src/abi.rs b/kernel/src/abi.rs
index 4463097..889a0f3 100644
--- a/kernel/src/abi.rs
+++ b/kernel/src/abi.rs
@@ -24,17 +24,23 @@ pub extern "Rust" fn print(msg: &str) {
     defmt::info!("{:?}", msg);
 }
 
+// TODO: maybe return result
 pub extern "Rust" fn draw_iter(pixels: &[Pixel<Rgb565>]) {
-    let framebuffer = block_on(FRAMEBUFFER.lock());
-    framebuffer
-        .borrow_mut()
-        .as_mut()
-        .unwrap()
-        .draw_iter(pixels.iter().copied())
-        .unwrap();
+    for _ in 0..10 {
+        if let Some(mut framebuffer) = FRAMEBUFFER.try_lock().ok() {
+            for _ in 0..10 {
+                // kernel takes() framebuffer
+                if let Some(framebuffer) = framebuffer.as_mut() {
+                    framebuffer.draw_iter(pixels.iter().copied()).unwrap();
+                }
+                break;
+            }
+            break;
+        }
+        cortex_m::asm::nop();
+    }
 }
 
 pub extern "Rust" fn get_key() -> Option<KeyEvent> {
-    defmt::info!("get key called");
     unsafe { KEY_CACHE.dequeue() }
 }
diff --git a/kernel/src/display.rs b/kernel/src/display.rs
index 388f9bf..7f27811 100644
--- a/kernel/src/display.rs
+++ b/kernel/src/display.rs
@@ -1,10 +1,9 @@
-use core::cell::RefCell;
 use embassy_rp::{
     gpio::{Level, Output},
     peripherals::{PIN_13, PIN_14, PIN_15, SPI1},
     spi::{Async, Spi},
 };
-use embassy_sync::{blocking_mutex::raw::ThreadModeRawMutex, mutex::Mutex};
+use embassy_sync::{blocking_mutex::raw::CriticalSectionRawMutex, mutex::Mutex};
 use embassy_time::{Delay, Timer};
 use embedded_hal_bus::spi::ExclusiveDevice;
 use st7365p_lcd::{FrameBuffer, ST7365P};
@@ -22,8 +21,7 @@ pub const SCREEN_HEIGHT: usize = 320;
 
 type FB = FrameBuffer<SCREEN_WIDTH, SCREEN_HEIGHT, { SCREEN_WIDTH * SCREEN_HEIGHT }>;
 static FRAMEBUFFER_CELL: StaticCell<FB> = StaticCell::new();
-pub static FRAMEBUFFER: Mutex<ThreadModeRawMutex, RefCell<Option<&'static mut FB>>> =
-    Mutex::new(RefCell::new(None));
+pub static FRAMEBUFFER: Mutex<CriticalSectionRawMutex, Option<&'static mut FB>> = Mutex::new(None);
 
 pub async fn init_display(
     spi: Spi<'static, SPI1, Async>,
@@ -45,25 +43,23 @@ pub async fn init_display(
     display.set_custom_orientation(0x40).await.unwrap();
     framebuffer.draw(&mut display).await.unwrap();
     display.set_on().await.unwrap();
-    FRAMEBUFFER
-        .lock()
-        .await
-        .swap(&RefCell::new(Some(framebuffer)));
+    FRAMEBUFFER.lock().await.replace(framebuffer);
 
     display
 }
 
 pub async fn display_handler(mut display: DISPLAY) {
     loop {
-        FRAMEBUFFER
-            .lock()
-            .await
-            .borrow_mut()
-            .as_mut()
-            .unwrap()
-            .partial_draw_batched(&mut display)
-            .await
-            .unwrap();
+        let fb: &mut FB = {
+            let mut guard = FRAMEBUFFER.lock().await;
+            guard.take().unwrap() // take ownership
+        }; // guard dropped
+
+        fb.partial_draw_batched(&mut display).await.unwrap();
+
+        // Put it back
+        FRAMEBUFFER.lock().await.replace(fb);
+
         Timer::after_millis(32).await; // 30 fps
     }
 }
diff --git a/kernel/src/main.rs b/kernel/src/main.rs
index 57b696e..27451df 100644
--- a/kernel/src/main.rs
+++ b/kernel/src/main.rs
@@ -181,8 +181,6 @@ async fn kernel_task(display: Display, sd: Sd, mcu: Mcu, usb: USB) {
     );
     let display = init_display(spi, display.cs, display.data, display.reset).await;
 
-    DRIVERS_READY.signal(());
-
     let display_fut = display_handler(display);
 
     {
@@ -204,6 +202,7 @@ async fn kernel_task(display: Display, sd: Sd, mcu: Mcu, usb: USB) {
     let usb_fut = usb_handler(usb);
 
     ENABLE_SCSI.store(true, core::sync::atomic::Ordering::Relaxed);
+    DRIVERS_READY.signal(());
     join3(usb_fut, display_fut, async {
         loop {
             Timer::after_millis(100).await;
diff --git a/kernel/src/ui.rs b/kernel/src/ui.rs
index acb80fd..18c8d1a 100644
--- a/kernel/src/ui.rs
+++ b/kernel/src/ui.rs
@@ -51,6 +51,9 @@ impl<const MAX_SELECTIONS: usize, const MAX_STR_LEN: usize> UI<MAX_SELECTIONS, M
     }
 
     async fn draw_selection(&mut self) {
+        let mut fb_lock = FRAMEBUFFER.lock().await;
+        let fb = fb_lock.as_mut().unwrap();
+
         let text_style = MonoTextStyle::new(&FONT_9X15, Rgb565::WHITE);
 
         let selection = Rectangle::new(
@@ -62,7 +65,7 @@ impl<const MAX_SELECTIONS: usize, const MAX_STR_LEN: usize> UI<MAX_SELECTIONS, M
 
         let Some(first) = file_names.next() else {
             Text::new("No Programs found on SD Card\nEnsure programs end with '.bin',\nand are located in the root directory",
-                Point::zero(), text_style).draw(*FRAMEBUFFER.lock().await.borrow_mut().as_mut().unwrap()).unwrap();
+                Point::zero(), text_style).draw(*fb).unwrap();
 
             return;
         };
@@ -72,18 +75,8 @@ impl<const MAX_SELECTIONS: usize, const MAX_STR_LEN: usize> UI<MAX_SELECTIONS, M
         LinearLayout::vertical(chain)
             .with_alignment(horizontal::Center)
             .arrange()
-            .align_to(
-                &FRAMEBUFFER
-                    .lock()
-                    .await
-                    .borrow_mut()
-                    .as_mut()
-                    .unwrap()
-                    .bounding_box(),
-                horizontal::Center,
-                vertical::Center,
-            )
-            .draw(*FRAMEBUFFER.lock().await.borrow_mut().as_mut().unwrap())
+            .align_to(&fb.bounding_box(), horizontal::Center, vertical::Center)
+            .draw(*fb)
             .unwrap();
     }
 }