Add DMA memcpy support to the S2 (#3352)

* Expose CopyDmaChannel

* Add DMA memcpy support to the S2

* whoops, esp32 is a thing

* clear can be a no-op

* sigh

* rust

* enable the DMA channel

* The S2 wants RX first...

* fmt

esp-hal/CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - All peripheral singletons (`GpioPin<...>`, `SPIn`, ...) now have a lifetime, as well as `steal`, `reborrow` and `clone_unchecked` methods (#3305)
 - `i2c::master::Operation` now implements `defmt::Format` (#3348)
 - ESP32-S2: Support for light-/deep-sleep (#3341) 
+- Add DMA memcpy support to the S2 (#3352)
 
 ### Changed
 

esp-hal/src/dma/m2m.rs

@@ -3,18 +3,23 @@ use core::{
     ops::{Deref, DerefMut},
 };
 
-use crate::{
+#[cfg(not(esp32s2))]
-    dma::{
+use crate::dma::{
     AnyGdmaChannel,
     AnyGdmaRxChannel,
     AnyGdmaTxChannel,
+    DmaChannelConvert,
+    DmaEligible,
+};
+#[cfg(esp32s2)]
+use crate::dma::{CopyDmaChannel, CopyDmaRxChannel, CopyDmaTxChannel};
+use crate::{
+    dma::{
         BurstConfig,
         Channel,
         ChannelRx,
         ChannelTx,
-        DmaChannelConvert,
         DmaDescriptor,
-        DmaEligible,
         DmaError,
         DmaPeripheral,
         DmaRxBuf,
@@ -46,6 +51,7 @@ where
 
 impl<'d> Mem2Mem<'d, Blocking> {
     /// Create a new Mem2Mem instance.
+    #[cfg(not(esp32s2))]
     pub fn new(
         channel: impl DmaChannelConvert<AnyGdmaChannel<'d>>,
         peripheral: impl DmaEligible,
@@ -59,6 +65,7 @@ impl<'d> Mem2Mem<'d, Blocking> {
     ///
     /// You must ensure that you're not using DMA for the same peripheral and
     /// that you're the only one using the DmaPeripheral.
+    #[cfg(not(esp32s2))]
     pub unsafe fn new_unsafe(
         channel: impl DmaChannelConvert<AnyGdmaChannel<'d>>,
         peripheral: DmaPeripheral,
@@ -79,6 +86,27 @@ impl<'d> Mem2Mem<'d, Blocking> {
         }
     }
 
+    /// Create a new Mem2Mem instance.
+    #[cfg(esp32s2)]
+    pub fn new(channel: CopyDmaChannel<'d>) -> Self {
+        let channel = Channel::new(channel);
+
+        // The S2's COPY DMA channel doesn't care about this. Once support for other
+        // channels are added, this will need updating.
+        let peripheral = DmaPeripheral::Spi2;
+
+        Mem2Mem {
+            rx: Mem2MemRx {
+                channel: channel.rx,
+                peripheral,
+            },
+            tx: Mem2MemTx {
+                channel: channel.tx,
+                peripheral,
+            },
+        }
+    }
+
     /// Shortcut to create a [SimpleMem2Mem]
     pub fn with_descriptors(
         self,
@@ -100,7 +128,10 @@ impl<'d> Mem2Mem<'d, Blocking> {
 
 /// The RX half of [Mem2Mem].
 pub struct Mem2MemRx<'d, Dm: DriverMode> {
+    #[cfg(not(esp32s2))]
     channel: ChannelRx<Dm, AnyGdmaRxChannel<'d>>,
+    #[cfg(esp32s2)]
+    channel: ChannelRx<Dm, CopyDmaRxChannel<'d>>,
     peripheral: DmaPeripheral,
 }
 
@@ -228,7 +259,10 @@ impl<M: DriverMode, BUF: DmaRxBuffer> Drop for Mem2MemRxTransfer<'_, M, BUF> {
 
 /// The TX half of [Mem2Mem].
 pub struct Mem2MemTx<'d, Dm: DriverMode> {
+    #[cfg(not(esp32s2))]
     channel: ChannelTx<Dm, AnyGdmaTxChannel<'d>>,
+    #[cfg(esp32s2)]
+    channel: ChannelTx<Dm, CopyDmaTxChannel<'d>>,
     peripheral: DmaPeripheral,
 }
 
@@ -417,23 +451,8 @@ impl<'d, Dm: DriverMode> SimpleMem2Mem<'d, Dm> {
             core::slice::from_raw_parts_mut(tx_descriptors.as_mut_ptr(), tx_descriptors.len())
         };
 
-        let dma_tx_buf = unwrap!(
+        // Note: The ESP32-S2 insists that RX is started before TX. Contrary to the TRM
-            DmaTxBuf::new_with_config(tx_descriptors, tx_buffer, self.config),
+        // and every other chip.
-            "There's no way to get the descriptors back yet"
-        );
-
-        let tx = match mem2mem.tx.send(dma_tx_buf) {
-            Ok(tx) => tx,
-            Err((err, tx, buf)) => {
-                let (tx_descriptors, _tx_buffer) = buf.split();
-                self.state = State::Idle(
-                    Mem2Mem { rx: mem2mem.rx, tx },
-                    rx_descriptors,
-                    tx_descriptors,
-                );
-                return Err(err);
-            }
-        };
 
         let dma_rx_buf = unwrap!(
             DmaRxBuf::new_with_config(rx_descriptors, rx_buffer, self.config),
@@ -444,8 +463,26 @@ impl<'d, Dm: DriverMode> SimpleMem2Mem<'d, Dm> {
             Ok(rx) => rx,
             Err((err, rx, buf)) => {
                 let (rx_descriptors, _rx_buffer) = buf.split();
-                let (tx, buf) = tx.stop();
+                self.state = State::Idle(
+                    Mem2Mem { rx, tx: mem2mem.tx },
+                    rx_descriptors,
+                    tx_descriptors,
+                );
+                return Err(err);
+            }
+        };
+
+        let dma_tx_buf = unwrap!(
+            DmaTxBuf::new_with_config(tx_descriptors, tx_buffer, self.config),
+            "There's no way to get the descriptors back yet"
+        );
+
+        let tx = match mem2mem.tx.send(dma_tx_buf) {
+            Ok(tx) => tx,
+            Err((err, tx, buf)) => {
                 let (tx_descriptors, _tx_buffer) = buf.split();
+                let (rx, buf) = rx.stop();
+                let (rx_descriptors, _rx_buffer) = buf.split();
                 self.state = State::Idle(Mem2Mem { rx, tx }, rx_descriptors, tx_descriptors);
                 return Err(err);
             }

esp-hal/src/dma/mod.rs

@@ -56,7 +56,7 @@ use enumset::{EnumSet, EnumSetType};
 pub use self::buffers::*;
 #[cfg(gdma)]
 pub use self::gdma::*;
-#[cfg(gdma)]
+#[cfg(any(gdma, esp32s2))]
 pub use self::m2m::*;
 #[cfg(pdma)]
 pub use self::pdma::*;
@@ -373,7 +373,7 @@ unsafe impl Send for DmaDescriptor {}
 mod buffers;
 #[cfg(gdma)]
 mod gdma;
-#[cfg(gdma)]
+#[cfg(any(gdma, esp32s2))]
 mod m2m;
 #[cfg(pdma)]
 mod pdma;

esp-hal/src/dma/pdma/copy.rs

@@ -0,0 +1,450 @@
+use portable_atomic::{AtomicBool, Ordering};
+
+use crate::{
+    asynch::AtomicWaker,
+    dma::*,
+    interrupt::{InterruptHandler, Priority},
+    peripherals::{Interrupt, COPY_DMA},
+};
+
+pub(super) type CopyRegisterBlock = crate::pac::copy_dma::RegisterBlock;
+
+/// The RX half of a Copy DMA channel.
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct CopyDmaRxChannel<'d>(pub(crate) CopyDmaChannel<'d>);
+
+impl CopyDmaRxChannel<'_> {
+    fn regs(&self) -> &CopyRegisterBlock {
+        self.0.register_block()
+    }
+}
+
+impl crate::private::Sealed for CopyDmaRxChannel<'_> {}
+impl DmaRxChannel for CopyDmaRxChannel<'_> {}
+
+/// The TX half of a Copy DMA channel.
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct CopyDmaTxChannel<'d>(pub(crate) CopyDmaChannel<'d>);
+
+impl CopyDmaTxChannel<'_> {
+    fn regs(&self) -> &CopyRegisterBlock {
+        self.0.register_block()
+    }
+}
+
+impl crate::private::Sealed for CopyDmaTxChannel<'_> {}
+impl DmaTxChannel for CopyDmaTxChannel<'_> {}
+
+impl RegisterAccess for CopyDmaTxChannel<'_> {
+    fn reset(&self) {
+        self.regs().conf().modify(|_, w| w.out_rst().set_bit());
+        self.regs().conf().modify(|_, w| w.out_rst().clear_bit());
+    }
+
+    fn set_burst_mode(&self, _burst_mode: BurstConfig) {}
+
+    fn set_descr_burst_mode(&self, _burst_mode: bool) {}
+
+    fn set_peripheral(&self, _peripheral: u8) {
+        // no-op
+    }
+
+    fn set_link_addr(&self, address: u32) {
+        self.regs()
+            .out_link()
+            .modify(|_, w| unsafe { w.outlink_addr().bits(address) });
+    }
+
+    fn start(&self) {
+        self.regs()
+            .out_link()
+            .modify(|_, w| w.outlink_start().set_bit());
+    }
+
+    fn stop(&self) {
+        self.regs()
+            .out_link()
+            .modify(|_, w| w.outlink_stop().set_bit());
+    }
+
+    fn restart(&self) {
+        self.regs()
+            .out_link()
+            .modify(|_, w| w.outlink_restart().set_bit());
+    }
+
+    fn set_check_owner(&self, check_owner: Option<bool>) {
+        if check_owner == Some(true) {
+            panic!("Copy DMA does not support checking descriptor ownership");
+        }
+    }
+
+    fn is_compatible_with(&self, peripheral: DmaPeripheral) -> bool {
+        self.0.is_compatible_with(peripheral)
+    }
+
+    #[cfg(psram_dma)]
+    fn set_ext_mem_block_size(&self, _size: DmaExtMemBKSize) {
+        // not supported
+    }
+
+    #[cfg(psram_dma)]
+    fn can_access_psram(&self) -> bool {
+        false
+    }
+}
+
+impl TxRegisterAccess for CopyDmaTxChannel<'_> {
+    fn is_fifo_empty(&self) -> bool {
+        self.regs().in_st().read().fifo_empty().bit()
+    }
+
+    fn set_auto_write_back(&self, enable: bool) {
+        self.regs()
+            .conf()
+            .modify(|_, w| w.out_auto_wrback().bit(enable));
+    }
+
+    fn last_dscr_address(&self) -> usize {
+        self.regs()
+            .out_eof_des_addr()
+            .read()
+            .out_eof_des_addr()
+            .bits() as usize
+    }
+
+    fn peripheral_interrupt(&self) -> Option<Interrupt> {
+        None
+    }
+
+    fn async_handler(&self) -> Option<InterruptHandler> {
+        None
+    }
+}
+
+impl InterruptAccess<DmaTxInterrupt> for CopyDmaTxChannel<'_> {
+    fn enable_listen(&self, interrupts: EnumSet<DmaTxInterrupt>, enable: bool) {
+        self.regs().int_ena().modify(|_, w| {
+            for interrupt in interrupts {
+                match interrupt {
+                    DmaTxInterrupt::TotalEof => w.out_total_eof().bit(enable),
+                    DmaTxInterrupt::DescriptorError => w.out_dscr_err().bit(enable),
+                    DmaTxInterrupt::Eof => w.out_eof().bit(enable),
+                    DmaTxInterrupt::Done => w.out_done().bit(enable),
+                };
+            }
+            w
+        });
+    }
+
+    fn is_listening(&self) -> EnumSet<DmaTxInterrupt> {
+        let mut result = EnumSet::new();
+
+        let int_ena = self.regs().int_ena().read();
+        if int_ena.out_total_eof().bit_is_set() {
+            result |= DmaTxInterrupt::TotalEof;
+        }
+        if int_ena.out_dscr_err().bit_is_set() {
+            result |= DmaTxInterrupt::DescriptorError;
+        }
+        if int_ena.out_eof().bit_is_set() {
+            result |= DmaTxInterrupt::Eof;
+        }
+        if int_ena.out_done().bit_is_set() {
+            result |= DmaTxInterrupt::Done;
+        }
+
+        result
+    }
+
+    fn clear(&self, interrupts: impl Into<EnumSet<DmaTxInterrupt>>) {
+        self.regs().int_clr().write(|w| {
+            for interrupt in interrupts.into() {
+                match interrupt {
+                    DmaTxInterrupt::TotalEof => w.out_total_eof().clear_bit_by_one(),
+                    DmaTxInterrupt::DescriptorError => w.out_dscr_err().clear_bit_by_one(),
+                    DmaTxInterrupt::Eof => w.out_eof().clear_bit_by_one(),
+                    DmaTxInterrupt::Done => w.out_done().clear_bit_by_one(),
+                };
+            }
+            w
+        });
+    }
+
+    fn pending_interrupts(&self) -> EnumSet<DmaTxInterrupt> {
+        let mut result = EnumSet::new();
+
+        let int_raw = self.regs().int_raw().read();
+        if int_raw.out_total_eof().bit_is_set() {
+            result |= DmaTxInterrupt::TotalEof;
+        }
+        if int_raw.out_dscr_err().bit_is_set() {
+            result |= DmaTxInterrupt::DescriptorError;
+        }
+        if int_raw.out_eof().bit_is_set() {
+            result |= DmaTxInterrupt::Eof;
+        }
+        if int_raw.out_done().bit_is_set() {
+            result |= DmaTxInterrupt::Done;
+        }
+
+        result
+    }
+
+    fn waker(&self) -> &'static AtomicWaker {
+        self.0.tx_waker()
+    }
+
+    fn is_async(&self) -> bool {
+        self.0.tx_async_flag().load(Ordering::Acquire)
+    }
+
+    fn set_async(&self, is_async: bool) {
+        self.0.tx_async_flag().store(is_async, Ordering::Release);
+    }
+}
+
+impl RegisterAccess for CopyDmaRxChannel<'_> {
+    fn reset(&self) {
+        self.regs().conf().modify(|_, w| w.in_rst().set_bit());
+        self.regs().conf().modify(|_, w| w.in_rst().clear_bit());
+    }
+
+    fn set_burst_mode(&self, _burst_mode: BurstConfig) {}
+
+    fn set_descr_burst_mode(&self, _burst_mode: bool) {}
+
+    fn set_peripheral(&self, _peripheral: u8) {
+        // no-op
+    }
+
+    fn set_link_addr(&self, address: u32) {
+        self.regs()
+            .in_link()
+            .modify(|_, w| unsafe { w.inlink_addr().bits(address) });
+    }
+
+    fn start(&self) {
+        self.regs()
+            .in_link()
+            .modify(|_, w| w.inlink_start().set_bit());
+    }
+
+    fn stop(&self) {
+        self.regs()
+            .in_link()
+            .modify(|_, w| w.inlink_stop().set_bit());
+    }
+
+    fn restart(&self) {
+        self.regs()
+            .in_link()
+            .modify(|_, w| w.inlink_restart().set_bit());
+    }
+
+    fn set_check_owner(&self, check_owner: Option<bool>) {
+        if check_owner == Some(true) {
+            panic!("Copy DMA does not support checking descriptor ownership");
+        }
+    }
+
+    fn is_compatible_with(&self, peripheral: DmaPeripheral) -> bool {
+        self.0.is_compatible_with(peripheral)
+    }
+
+    #[cfg(psram_dma)]
+    fn set_ext_mem_block_size(&self, _size: DmaExtMemBKSize) {
+        // not supported
+    }
+
+    #[cfg(psram_dma)]
+    fn can_access_psram(&self) -> bool {
+        false
+    }
+}
+
+impl RxRegisterAccess for CopyDmaRxChannel<'_> {
+    fn peripheral_interrupt(&self) -> Option<Interrupt> {
+        None
+    }
+
+    fn async_handler(&self) -> Option<InterruptHandler> {
+        None
+    }
+}
+
+impl InterruptAccess<DmaRxInterrupt> for CopyDmaRxChannel<'_> {
+    fn enable_listen(&self, interrupts: EnumSet<DmaRxInterrupt>, enable: bool) {
+        self.regs().int_ena().modify(|_, w| {
+            for interrupt in interrupts {
+                match interrupt {
+                    DmaRxInterrupt::SuccessfulEof => w.in_suc_eof().bit(enable),
+                    DmaRxInterrupt::ErrorEof => unimplemented!(),
+                    DmaRxInterrupt::DescriptorError => w.in_dscr_err().bit(enable),
+                    DmaRxInterrupt::DescriptorEmpty => w.in_dscr_empty().bit(enable),
+                    DmaRxInterrupt::Done => w.in_done().bit(enable),
+                };
+            }
+            w
+        });
+    }
+
+    fn is_listening(&self) -> EnumSet<DmaRxInterrupt> {
+        let mut result = EnumSet::new();
+
+        let int_ena = self.regs().int_ena().read();
+        if int_ena.in_dscr_err().bit_is_set() {
+            result |= DmaRxInterrupt::DescriptorError;
+        }
+        if int_ena.in_dscr_err().bit_is_set() {
+            result |= DmaRxInterrupt::DescriptorEmpty;
+        }
+        if int_ena.in_suc_eof().bit_is_set() {
+            result |= DmaRxInterrupt::SuccessfulEof;
+        }
+        if int_ena.in_done().bit_is_set() {
+            result |= DmaRxInterrupt::Done;
+        }
+
+        result
+    }
+
+    fn clear(&self, interrupts: impl Into<EnumSet<DmaRxInterrupt>>) {
+        self.regs().int_clr().write(|w| {
+            for interrupt in interrupts.into() {
+                match interrupt {
+                    DmaRxInterrupt::SuccessfulEof => w.in_suc_eof().clear_bit_by_one(),
+                    DmaRxInterrupt::ErrorEof => continue,
+                    DmaRxInterrupt::DescriptorError => w.in_dscr_err().clear_bit_by_one(),
+                    DmaRxInterrupt::DescriptorEmpty => w.in_dscr_empty().clear_bit_by_one(),
+                    DmaRxInterrupt::Done => w.in_done().clear_bit_by_one(),
+                };
+            }
+            w
+        });
+    }
+
+    fn pending_interrupts(&self) -> EnumSet<DmaRxInterrupt> {
+        let mut result = EnumSet::new();
+
+        let int_raw = self.regs().int_raw().read();
+        if int_raw.in_dscr_err().bit_is_set() {
+            result |= DmaRxInterrupt::DescriptorError;
+        }
+        if int_raw.in_dscr_empty().bit_is_set() {
+            result |= DmaRxInterrupt::DescriptorEmpty;
+        }
+        if int_raw.in_suc_eof().bit_is_set() {
+            result |= DmaRxInterrupt::SuccessfulEof;
+        }
+        if int_raw.in_done().bit_is_set() {
+            result |= DmaRxInterrupt::Done;
+        }
+
+        result
+    }
+
+    fn waker(&self) -> &'static AtomicWaker {
+        self.0.rx_waker()
+    }
+
+    fn is_async(&self) -> bool {
+        self.0.rx_async_flag().load(Ordering::Relaxed)
+    }
+
+    fn set_async(&self, _is_async: bool) {
+        self.0.rx_async_flag().store(_is_async, Ordering::Relaxed);
+    }
+}
+
+#[doc = "DMA channel suitable for COPY"]
+#[non_exhaustive]
+#[derive(Debug)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+pub struct CopyDmaChannel<'d> {
+    _lifetime: core::marker::PhantomData<&'d mut ()>,
+}
+
+impl crate::private::Sealed for CopyDmaChannel<'_> {}
+
+impl CopyDmaChannel<'_> {
+    #[doc = r" Unsafely constructs a new DMA channel."]
+    #[doc = r""]
+    #[doc = r" # Safety"]
+    #[doc = r""]
+    #[doc = r" The caller must ensure that only a single instance is used."]
+    pub unsafe fn steal() -> Self {
+        Self {
+            _lifetime: core::marker::PhantomData,
+        }
+    }
+}
+impl<'d> DmaChannel for CopyDmaChannel<'d> {
+    type Rx = CopyDmaRxChannel<'d>;
+    type Tx = CopyDmaTxChannel<'d>;
+    unsafe fn split_internal(self, _: crate::private::Internal) -> (Self::Rx, Self::Tx) {
+        (
+            CopyDmaRxChannel(unsafe { Self::steal() }),
+            CopyDmaTxChannel(unsafe { Self::steal() }),
+        )
+    }
+}
+impl DmaChannelExt for CopyDmaChannel<'_> {
+    fn rx_interrupts() -> impl InterruptAccess<DmaRxInterrupt> {
+        CopyDmaRxChannel(unsafe { Self::steal() })
+    }
+    fn tx_interrupts() -> impl InterruptAccess<DmaTxInterrupt> {
+        CopyDmaTxChannel(unsafe { Self::steal() })
+    }
+}
+impl PdmaChannel for CopyDmaChannel<'_> {
+    type RegisterBlock = CopyRegisterBlock;
+    fn register_block(&self) -> &Self::RegisterBlock {
+        COPY_DMA::regs()
+    }
+    fn tx_waker(&self) -> &'static AtomicWaker {
+        static WAKER: AtomicWaker = AtomicWaker::new();
+        &WAKER
+    }
+    fn rx_waker(&self) -> &'static AtomicWaker {
+        static WAKER: AtomicWaker = AtomicWaker::new();
+        &WAKER
+    }
+    fn is_compatible_with(&self, peripheral: DmaPeripheral) -> bool {
+        let compatible_peripherals = [DmaPeripheral::Aes, DmaPeripheral::Sha];
+        compatible_peripherals.contains(&peripheral)
+    }
+    fn peripheral_interrupt(&self) -> Interrupt {
+        Interrupt::DMA_COPY
+    }
+    fn async_handler(&self) -> InterruptHandler {
+        pub(crate) extern "C" fn __esp_hal_internal_interrupt_handler() {
+            super::asynch::handle_in_interrupt::<CopyDmaChannel<'static>>();
+            super::asynch::handle_out_interrupt::<CopyDmaChannel<'static>>();
+        }
+        #[allow(non_upper_case_globals)]
+        pub(crate) static interrupt_handler: InterruptHandler =
+            InterruptHandler::new(__esp_hal_internal_interrupt_handler, Priority::max());
+        interrupt_handler
+    }
+    fn rx_async_flag(&self) -> &'static AtomicBool {
+        static FLAG: AtomicBool = AtomicBool::new(false);
+        &FLAG
+    }
+    fn tx_async_flag(&self) -> &'static AtomicBool {
+        static FLAG: AtomicBool = AtomicBool::new(false);
+        &FLAG
+    }
+}
+impl<'d> DmaChannelConvert<CopyDmaRxChannel<'d>> for CopyDmaChannel<'d> {
+    fn degrade(self) -> CopyDmaRxChannel<'d> {
+        CopyDmaRxChannel(self)
+    }
+}
+impl<'d> DmaChannelConvert<CopyDmaTxChannel<'d>> for CopyDmaChannel<'d> {
+    fn degrade(self) -> CopyDmaTxChannel<'d> {
+        CopyDmaTxChannel(self)
+    }
+}

esp-hal/src/dma/pdma/mod.rs

@@ -16,11 +16,15 @@ use portable_atomic::AtomicBool;
 
 use crate::{asynch::AtomicWaker, dma::*, handler, interrupt::Priority, peripherals::Interrupt};
 
+#[cfg(esp32s2)]
+mod copy;
 #[cfg(esp32s2)]
 mod crypto;
 mod i2s;
 mod spi;
 
+#[cfg(esp32s2)]
+pub use copy::*;
 #[cfg(esp32s2)]
 pub use crypto::*;
 pub use i2s::*;
@@ -164,6 +168,18 @@ pub(super) fn init_dma(_cs: CriticalSection<'_>) {
             .spi_dma_chan_sel()
             .modify(|_, w| unsafe { w.spi2_dma_chan_sel().bits(1).spi3_dma_chan_sel().bits(2) });
     }
+
+    #[cfg(esp32s2)]
+    {
+        // This is the only DMA channel on the S2 that needs to be enabled this way
+        // (using its own registers). Ideally this should be enabled only when
+        // the DMA channel is in use but we don't have a good mechanism for that
+        // yet. For now, we shall just turn in on forever once any DMA channel is used.
+
+        use crate::peripherals::COPY_DMA;
+
+        COPY_DMA::regs().conf().modify(|_, w| w.clk_en().set_bit());
+    }
 }
 
 impl<CH, Dm> Channel<Dm, CH>

esp-hal/src/soc/esp32s2/peripherals.rs

@@ -33,6 +33,7 @@ crate::peripherals! {
         APB_SARADC <= APB_SARADC,
         DAC1 <= virtual,
         DAC2 <= virtual,
+        COPY_DMA <= COPY_DMA,
         CRYPTO_DMA <= CRYPTO_DMA,
         DEDICATED_GPIO <= DEDICATED_GPIO,
         DS <= DS,
@@ -128,5 +129,6 @@ crate::peripherals! {
         DMA_SPI3: Spi3DmaChannel,
         DMA_I2S0: I2s0DmaChannel,
         DMA_CRYPTO: CryptoDmaChannel,
+        DMA_COPY: CopyDmaChannel,
     ]
 }

examples/src/bin/dma_mem2mem.rs

@@ -1,7 +1,7 @@
 //! Uses DMA to copy memory to memory.
 
 //% FEATURES: esp-hal/log esp-hal/unstable
-//% CHIPS: esp32s3 esp32c2 esp32c3 esp32c6 esp32h2
+//% CHIPS: esp32s2 esp32s3 esp32c2 esp32c3 esp32c6 esp32h2
 
 #![no_std]
 #![no_main]
@@ -29,18 +29,20 @@ fn main() -> ! {
     let (rx_buffer, rx_descriptors, tx_buffer, tx_descriptors) = dma_buffers!(DATA_SIZE);
 
     cfg_if::cfg_if! {
-        if #[cfg(any(feature = "esp32c2", feature = "esp32c3", feature = "esp32s3"))] {
+        if #[cfg(feature = "esp32s2")] {
-            let dma_peripheral = peripherals.SPI2;
+            let mem2mem = Mem2Mem::new(peripherals.DMA_COPY);
+        } else if #[cfg(any(feature = "esp32c2", feature = "esp32c3", feature = "esp32s3"))] {
+            let mem2mem = Mem2Mem::new(peripherals.DMA_CH0, peripherals.SPI2);
         } else {
-            let dma_peripheral = peripherals.MEM2MEM1;
+            let mem2mem = Mem2Mem::new(peripherals.DMA_CH0, peripherals.MEM2MEM1);
         }
     }
 
-    let mut mem2mem = Mem2Mem::new(peripherals.DMA_CH0, dma_peripheral)
+    let mut mem2mem = mem2mem
         .with_descriptors(rx_descriptors, tx_descriptors, BurstConfig::default())
         .unwrap();
 
-    for i in 0..core::mem::size_of_val(tx_buffer) {
+    for i in 0..size_of_val(tx_buffer) {
         tx_buffer[i] = (i % 256) as u8;
     }
 
@@ -52,7 +54,7 @@ fn main() -> ! {
             dma_wait.wait().unwrap();
             info!("Transfer completed, comparing buffer");
             let mut error = false;
-            for i in 0..core::mem::size_of_val(tx_buffer) {
+            for i in 0..size_of_val(tx_buffer) {
                 if rx_buffer[i] != tx_buffer[i] {
                     error!(
                         "Error: tx_buffer[{}] = {}, rx_buffer[{}] = {}",

hil-test/tests/dma_mem2mem.rs

@@ -1,31 +1,23 @@
 //! DMA Mem2Mem Tests
 
-//% CHIPS: esp32c2 esp32c3 esp32c6 esp32h2 esp32s3
+//% CHIPS: esp32c2 esp32c3 esp32c6 esp32h2 esp32s2 esp32s3
 //% FEATURES: unstable
 
 #![no_std]
 #![no_main]
 
 use esp_hal::{
-    dma::{AnyGdmaChannel, DmaChannelConvert, DmaError, Mem2Mem},
+    dma::{DmaError, Mem2Mem},
     dma_buffers,
     dma_descriptors,
+    Blocking,
 };
 use hil_test as _;
 
 const DATA_SIZE: usize = 1024 * 10;
 
-cfg_if::cfg_if! {
-    if #[cfg(any(esp32c2, esp32c6, esp32h2))] {
-        type DmaPeripheralType<'d> = esp_hal::peripherals::MEM2MEM1<'d>;
-    } else {
-        type DmaPeripheralType<'d> = esp_hal::peripherals::SPI2<'d>;
-    }
-}
-
 struct Context {
-    channel: AnyGdmaChannel<'static>,
+    mem2mem: Mem2Mem<'static, Blocking>,
-    dma_peripheral: DmaPeripheralType<'static>,
 }
 
 #[cfg(test)]
@@ -37,27 +29,25 @@ mod tests {
     fn init() -> Context {
         let peripherals = esp_hal::init(esp_hal::Config::default());
 
-        let dma_channel = peripherals.DMA_CH0;
-
         cfg_if::cfg_if! {
-            if #[cfg(any(esp32c2, esp32c6, esp32h2))] {
+            if #[cfg(esp32s2)] {
-                let dma_peripheral = peripherals.MEM2MEM1;
+                let mem2mem = Mem2Mem::new(peripherals.DMA_COPY);
+            } else if #[cfg(any(esp32c2, esp32c6, esp32h2))] {
+                let mem2mem = Mem2Mem::new(peripherals.DMA_CH0, peripherals.MEM2MEM1);
             } else {
-                let dma_peripheral = peripherals.SPI2;
+                let mem2mem = Mem2Mem::new(peripherals.DMA_CH0, peripherals.SPI2);
             }
         }
 
-        Context {
+        Context { mem2mem }
-            channel: dma_channel.degrade(),
-            dma_peripheral,
-        }
     }
 
     #[test]
     fn test_internal_mem2mem(ctx: Context) {
         let (rx_buffer, rx_descriptors, tx_buffer, tx_descriptors) = dma_buffers!(DATA_SIZE);
 
-        let mut mem2mem = Mem2Mem::new(ctx.channel, ctx.dma_peripheral)
+        let mut mem2mem = ctx
+            .mem2mem
             .with_descriptors(rx_descriptors, tx_descriptors, Default::default())
             .unwrap();
 
@@ -74,11 +64,10 @@ mod tests {
     #[test]
     fn test_mem2mem_errors_zero_tx(ctx: Context) {
         let (rx_descriptors, tx_descriptors) = dma_descriptors!(1024, 0);
-        match Mem2Mem::new(ctx.channel, ctx.dma_peripheral).with_descriptors(
+        match ctx
-            rx_descriptors,
+            .mem2mem
-            tx_descriptors,
+            .with_descriptors(rx_descriptors, tx_descriptors, Default::default())
-            Default::default(),
+        {
-        ) {
             Err(DmaError::OutOfDescriptors) => (),
             _ => panic!("Expected OutOfDescriptors"),
         }
@@ -87,11 +76,10 @@ mod tests {
     #[test]
     fn test_mem2mem_errors_zero_rx(ctx: Context) {
         let (rx_descriptors, tx_descriptors) = dma_descriptors!(0, 1024);
-        match Mem2Mem::new(ctx.channel, ctx.dma_peripheral).with_descriptors(
+        match ctx
-            rx_descriptors,
+            .mem2mem
-            tx_descriptors,
+            .with_descriptors(rx_descriptors, tx_descriptors, Default::default())
-            Default::default(),
+        {
-        ) {
             Err(DmaError::OutOfDescriptors) => (),
             _ => panic!("Expected OutOfDescriptors"),
         }