Merge pull request #1880 from phire/rp_bootsel

rp2040: BOOTSEL button support

4 files changed, 150 insertions, 39 deletions

diff --git a/embassy-rp/src/bootsel.rs b/embassy-rp/src/bootsel.rs
new file mode 100644
index 000000000..540255ae3
--- /dev/null
+++ b/embassy-rp/src/bootsel.rs
@@ -0,0 +1,83 @@
+//! Boot Select button
+//!
+//! The RP2040 rom supports a BOOTSEL button that is used to enter the USB bootloader
+//! if held during reset. To avoid wasting GPIO pins, the button is multiplexed onto
+//! the CS pin of the QSPI flash, but that makes it somewhat expensive and complicated
+//! to utilize outside of the rom's bootloader.
+//!
+//! This module provides functionality to poll BOOTSEL from an embassy application.
+
+use crate::flash::in_ram;
+
+impl crate::peripherals::BOOTSEL {
+    /// Polls the BOOTSEL button. Returns true if the button is pressed.
+    ///
+    /// Polling isn't cheap, as this function waits for core 1 to finish it's current
+    /// task and for any DMAs from flash to complete
+    pub fn is_pressed(&mut self) -> bool {
+        let mut cs_status = Default::default();
+
+        unsafe { in_ram(|| cs_status = ram_helpers::read_cs_status()) }.expect("Must be called from Core 0");
+
+        // bootsel is active low, so invert
+        !cs_status.infrompad()
+    }
+}
+
+mod ram_helpers {
+    use rp_pac::io::regs::GpioStatus;
+
+    /// Temporally reconfigures the CS gpio and returns the GpioStatus.
+
+    /// This function runs from RAM so it can disable flash XIP.
+    ///
+    /// # Safety
+    ///
+    /// The caller must ensure flash is idle and will remain idle.
+    /// This function must live in ram. It uses inline asm to avoid any
+    /// potential calls to ABI functions that might be in flash.
+    #[inline(never)]
+    #[link_section = ".data.ram_func"]
+    #[cfg(target_arch = "arm")]
+    pub unsafe fn read_cs_status() -> GpioStatus {
+        let result: u32;
+
+        // Magic value, used as both OEOVER::DISABLE and delay loop counter
+        let magic = 0x2000;
+
+        core::arch::asm!(
+            ".equiv GPIO_STATUS, 0x0",
+            ".equiv GPIO_CTRL,   0x4",
+
+            "ldr {orig_ctrl}, [{cs_gpio}, $GPIO_CTRL]",
+
+            // The BOOTSEL pulls the flash's CS line low though a 1K resistor.
+            // this is weak enough to avoid disrupting normal operation.
+            // But, if we disable CS's output drive and allow it to float...
+            "str {val}, [{cs_gpio}, $GPIO_CTRL]",
+
+            // ...then wait for the state to settle...
+            "1:", // ~4000 cycle delay loop
+            "subs {val}, #8",
+            "bne 1b",
+
+            // ...we can read the current state of bootsel
+            "ldr {val}, [{cs_gpio}, $GPIO_STATUS]",
+
+            // Finally, restore CS to normal operation so XIP can continue
+            "str {orig_ctrl}, [{cs_gpio}, $GPIO_CTRL]",
+
+            cs_gpio = in(reg) rp_pac::IO_QSPI.gpio(1).as_ptr(),
+            orig_ctrl = out(reg) _,
+            val = inout(reg) magic => result,
+            options(nostack),
+        );
+
+        core::mem::transmute(result)
+    }
+
+    #[cfg(not(target_arch = "arm"))]
+    pub unsafe fn read_cs_status() -> GpioStatus {
+        unimplemented!()
+    }
+}
diff --git a/embassy-rp/src/flash.rs b/embassy-rp/src/flash.rs
index 1c1c2449e..8fb5542f1 100644
--- a/embassy-rp/src/flash.rs
+++ b/embassy-rp/src/flash.rs
@@ -131,7 +131,7 @@ impl<'d, T: Instance, M: Mode, const FLASH_SIZE: usize> Flash<'d, T, M, FLASH_SI
 
         let len = to - from;
 
-        unsafe { self.in_ram(|| ram_helpers::flash_range_erase(from, len))? };
+        unsafe { in_ram(|| ram_helpers::flash_range_erase(from, len))? };
 
         Ok(())
     }
@@ -156,7 +156,7 @@ impl<'d, T: Instance, M: Mode, const FLASH_SIZE: usize> Flash<'d, T, M, FLASH_SI
 
             let unaligned_offset = offset as usize - start;
 
-            unsafe { self.in_ram(|| ram_helpers::flash_range_program(unaligned_offset as u32, &pad_buf))? }
+            unsafe { in_ram(|| ram_helpers::flash_range_program(unaligned_offset as u32, &pad_buf))? }
         }
 
         let remaining_len = bytes.len() - start_padding;
@@ -174,12 +174,12 @@ impl<'d, T: Instance, M: Mode, const FLASH_SIZE: usize> Flash<'d, T, M, FLASH_SI
             if bytes.as_ptr() as usize >= 0x2000_0000 {
                 let aligned_data = &bytes[start_padding..end_padding];
 
-                unsafe { self.in_ram(|| ram_helpers::flash_range_program(aligned_offset as u32, aligned_data))? }
+                unsafe { in_ram(|| ram_helpers::flash_range_program(aligned_offset as u32, aligned_data))? }
             } else {
                 for chunk in bytes[start_padding..end_padding].chunks_exact(PAGE_SIZE) {
                     let mut ram_buf = [0xFF_u8; PAGE_SIZE];
                     ram_buf.copy_from_slice(chunk);
-                    unsafe { self.in_ram(|| ram_helpers::flash_range_program(aligned_offset as u32, &ram_buf))? }
+                    unsafe { in_ram(|| ram_helpers::flash_range_program(aligned_offset as u32, &ram_buf))? }
                     aligned_offset += PAGE_SIZE;
                 }
             }
@@ -194,47 +194,15 @@ impl<'d, T: Instance, M: Mode, const FLASH_SIZE: usize> Flash<'d, T, M, FLASH_SI
 
             let unaligned_offset = end_offset - (PAGE_SIZE - rem_offset);
 
-            unsafe { self.in_ram(|| ram_helpers::flash_range_program(unaligned_offset as u32, &pad_buf))? }
+            unsafe { in_ram(|| ram_helpers::flash_range_program(unaligned_offset as u32, &pad_buf))? }
         }
 
         Ok(())
     }
 
-    /// Make sure to uphold the contract points with rp2040-flash.
-    /// - interrupts must be disabled
-    /// - DMA must not access flash memory
-    unsafe fn in_ram(&mut self, operation: impl FnOnce()) -> Result<(), Error> {
-        // Make sure we're running on CORE0
-        let core_id: u32 = pac::SIO.cpuid().read();
-        if core_id != 0 {
-            return Err(Error::InvalidCore);
-        }
-
-        // Make sure CORE1 is paused during the entire duration of the RAM function
-        crate::multicore::pause_core1();
-
-        critical_section::with(|_| {
-            // Wait for all DMA channels in flash to finish before ram operation
-            const SRAM_LOWER: u32 = 0x2000_0000;
-            for n in 0..crate::dma::CHANNEL_COUNT {
-                let ch = crate::pac::DMA.ch(n);
-                while ch.read_addr().read() < SRAM_LOWER && ch.ctrl_trig().read().busy() {}
-            }
-            // Wait for completion of any background reads
-            while pac::XIP_CTRL.stream_ctr().read().0 > 0 {}
-
-            // Run our flash operation in RAM
-            operation();
-        });
-
-        // Resume CORE1 execution
-        crate::multicore::resume_core1();
-        Ok(())
-    }
-
     /// Read SPI flash unique ID
     pub fn blocking_unique_id(&mut self, uid: &mut [u8]) -> Result<(), Error> {
-        unsafe { self.in_ram(|| ram_helpers::flash_unique_id(uid))? };
+        unsafe { in_ram(|| ram_helpers::flash_unique_id(uid))? };
         Ok(())
     }
 
@@ -242,7 +210,7 @@ impl<'d, T: Instance, M: Mode, const FLASH_SIZE: usize> Flash<'d, T, M, FLASH_SI
     pub fn blocking_jedec_id(&mut self) -> Result<u32, Error> {
         let mut jedec = None;
         unsafe {
-            self.in_ram(|| {
+            in_ram(|| {
                 jedec.replace(ram_helpers::flash_jedec_id());
             })?;
         };
@@ -871,6 +839,38 @@ mod ram_helpers {
     }
 }
 
+/// Make sure to uphold the contract points with rp2040-flash.
+/// - interrupts must be disabled
+/// - DMA must not access flash memory
+pub(crate) unsafe fn in_ram(operation: impl FnOnce()) -> Result<(), Error> {
+    // Make sure we're running on CORE0
+    let core_id: u32 = pac::SIO.cpuid().read();
+    if core_id != 0 {
+        return Err(Error::InvalidCore);
+    }
+
+    // Make sure CORE1 is paused during the entire duration of the RAM function
+    crate::multicore::pause_core1();
+
+    critical_section::with(|_| {
+        // Wait for all DMA channels in flash to finish before ram operation
+        const SRAM_LOWER: u32 = 0x2000_0000;
+        for n in 0..crate::dma::CHANNEL_COUNT {
+            let ch = crate::pac::DMA.ch(n);
+            while ch.read_addr().read() < SRAM_LOWER && ch.ctrl_trig().read().busy() {}
+        }
+        // Wait for completion of any background reads
+        while pac::XIP_CTRL.stream_ctr().read().0 > 0 {}
+
+        // Run our flash operation in RAM
+        operation();
+    });
+
+    // Resume CORE1 execution
+    crate::multicore::resume_core1();
+    Ok(())
+}
+
 mod sealed {
     pub trait Instance {}
     pub trait Mode {}
diff --git a/embassy-rp/src/lib.rs b/embassy-rp/src/lib.rs
index e8f818bcf..2728395b2 100644
--- a/embassy-rp/src/lib.rs
+++ b/embassy-rp/src/lib.rs
@@ -10,6 +10,7 @@ mod critical_section_impl;
 mod intrinsics;
 
 pub mod adc;
+pub mod bootsel;
 pub mod clocks;
 pub mod dma;
 pub mod flash;
@@ -193,6 +194,7 @@ embassy_hal_internal::peripherals! {
     PIO1,
 
     WATCHDOG,
+    BOOTSEL,
 }
 
 macro_rules! select_bootloader {
diff --git a/tests/rp/src/bin/bootsel.rs b/tests/rp/src/bin/bootsel.rs
new file mode 100644
index 000000000..df1ed8d2e
--- /dev/null
+++ b/tests/rp/src/bin/bootsel.rs
@@ -0,0 +1,26 @@
+#![no_std]
+#![no_main]
+#![feature(type_alias_impl_trait)]
+teleprobe_meta::target!(b"rpi-pico");
+
+use defmt::{assert_eq, *};
+use embassy_executor::Spawner;
+use embassy_time::{Duration, Timer};
+use {defmt_rtt as _, panic_probe as _};
+
+#[embassy_executor::main]
+async fn main(_spawner: Spawner) {
+    let mut p = embassy_rp::init(Default::default());
+    info!("Hello World!");
+
+    // add some delay to give an attached debug probe time to parse the
+    // defmt RTT header. Reading that header might touch flash memory, which
+    // interferes with flash write operations.
+    // https://github.com/knurling-rs/defmt/pull/683
+    Timer::after(Duration::from_millis(10)).await;
+
+    assert_eq!(p.BOOTSEL.is_pressed(), false);
+
+    info!("Test OK");
+    cortex_m::asm::bkpt();
+}