Fix LCD_CAM disabling its clocks (#3007)

esp-hal/CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - `DmaDescriptor` is now `#[repr(C)]` (#2988)
+- Fixed an issue that caused LCD_CAM drivers to turn off their clocks unexpectedly (#3007)
 
 ### Removed
 

esp-hal/src/lcd_cam/lcd/dpi.rs

@@ -115,6 +115,7 @@ use crate::{
     },
     peripheral::{Peripheral, PeripheralRef},
     peripherals::LCD_CAM,
+    system::{self, GenericPeripheralGuard},
     Blocking,
     DriverMode,
 };
@@ -131,6 +132,7 @@ pub enum ConfigError {
 pub struct Dpi<'d, Dm: DriverMode> {
     lcd_cam: PeripheralRef<'d, LCD_CAM>,
     tx_channel: ChannelTx<'d, Blocking, PeripheralTxChannel<LCD_CAM>>,
+    _guard: GenericPeripheralGuard<{ system::Peripheral::LcdCam as u8 }>,
     _mode: PhantomData<Dm>,
 }
 
@@ -152,6 +154,7 @@ where
         let mut this = Self {
             lcd_cam: lcd.lcd_cam,
             tx_channel,
+            _guard: lcd._guard,
             _mode: PhantomData,
         };
 

esp-hal/src/lcd_cam/lcd/i8080.rs

@@ -79,6 +79,7 @@ use crate::{
     },
     peripheral::{Peripheral, PeripheralRef},
     peripherals::LCD_CAM,
+    system::{self, GenericPeripheralGuard},
     Blocking,
     DriverMode,
 };
@@ -95,6 +96,7 @@ pub enum ConfigError {
 pub struct I8080<'d, Dm: DriverMode> {
     lcd_cam: PeripheralRef<'d, LCD_CAM>,
     tx_channel: ChannelTx<'d, Blocking, PeripheralTxChannel<LCD_CAM>>,
+    _guard: GenericPeripheralGuard<{ system::Peripheral::LcdCam as u8 }>,
     _mode: PhantomData<Dm>,
 }
 
@@ -118,6 +120,7 @@ where
         let mut this = Self {
             lcd_cam: lcd.lcd_cam,
             tx_channel,
+            _guard: lcd._guard,
             _mode: PhantomData,
         };
 

esp-hal/src/system.rs

@@ -1066,12 +1066,14 @@ impl PeripheralClockControl {
             if enable {
                 let prev = *ref_count;
                 *ref_count += 1;
+                trace!("Enable {:?} {} -> {}", peripheral, prev, *ref_count);
                 if prev > 0 {
                     return false;
                 }
             } else {
                 let prev = *ref_count;
                 *ref_count -= 1;
+                trace!("Disable {:?} {} -> {}", peripheral, prev, *ref_count);
                 if prev > 1 {
                     return false;
                 }

hil-test/tests/lcd_cam_i8080.rs

@@ -147,6 +147,10 @@ mod tests {
         .with_cs(cs_signal)
         .with_ctrl_pins(NoPin, NoPin);
 
+        // explicitly drop the camera half to see if it disables clocks (unexpectedly,
+        // I8080 should keep it alive)
+        core::mem::drop(ctx.lcd_cam.cam);
+
         // This is to make the test values look more intuitive.
         i8080.set_bit_order(BitOrder::Inverted);
 

hil-test/tests/lcd_cam_i8080_async.rs

@@ -58,6 +58,10 @@ mod tests {
         })
         .unwrap();
 
+        // explicitly drop the camera half to see if it disables clocks (unexpectedly,
+        // I8080 should keep it alive)
+        core::mem::drop(ctx.lcd_cam.cam);
+
         let mut transfer = i8080.send(Command::<u8>::None, 0, ctx.dma_buf).unwrap();
 
         transfer.wait_for_done().await;