diff --git a/embassy-rp/src/dma.rs b/embassy-rp/src/dma.rs index 05adcecd..ba07a88d 100644 --- a/embassy-rp/src/dma.rs +++ b/embassy-rp/src/dma.rs @@ -1,3 +1,4 @@ +//! Direct Memory Access (DMA) use core::future::Future; use core::pin::Pin; use core::sync::atomic::{compiler_fence, Ordering}; diff --git a/embassy-rp/src/spi.rs b/embassy-rp/src/spi.rs index 584370d5..c48e33fc 100644 --- a/embassy-rp/src/spi.rs +++ b/embassy-rp/src/spi.rs @@ -1,3 +1,4 @@ +//! Serial Peripheral Interface use core::marker::PhantomData; use embassy_embedded_hal::SetConfig; @@ -385,19 +386,36 @@ impl<'d, T: Instance> Spi<'d, T, Async> { async fn transfer_inner(&mut self, rx_ptr: *mut [u8], tx_ptr: *const [u8]) -> Result<(), Error> { let (_, from_len) = crate::dma::slice_ptr_parts(tx_ptr); let (_, to_len) = crate::dma::slice_ptr_parts_mut(rx_ptr); - assert_eq!(from_len, to_len); + unsafe { self.inner.regs().dmacr().write(|reg| { reg.set_rxdmae(true); reg.set_txdmae(true); }) }; - let tx_ch = self.tx_dma.as_mut().unwrap(); - let tx_transfer = unsafe { - // If we don't assign future to a variable, the data register pointer - // is held across an await and makes the future non-Send. - crate::dma::write(tx_ch, tx_ptr, self.inner.regs().dr().ptr() as *mut _, T::TX_DREQ) + + let mut tx_ch = self.tx_dma.as_mut().unwrap(); + // If we don't assign future to a variable, the data register pointer + // is held across an await and makes the future non-Send. + let tx_transfer = async { + let p = self.inner.regs(); + unsafe { + crate::dma::write(&mut tx_ch, tx_ptr, p.dr().ptr() as *mut _, T::TX_DREQ).await; + + if from_len > to_len { + let write_bytes_len = from_len - to_len; + // disable incrementation of buffer + tx_ch.regs().ctrl_trig().modify(|ctrl_trig| { + ctrl_trig.set_incr_write(false); + ctrl_trig.set_incr_read(false); + }); + + // write dummy data + crate::dma::write_repeated(tx_ch, p.dr().ptr() as *mut u8, write_bytes_len, T::TX_DREQ).await + } + } }; + let rx_ch = self.rx_dma.as_mut().unwrap(); let rx_transfer = unsafe { // If we don't assign future to a variable, the data register pointer @@ -405,6 +423,22 @@ impl<'d, T: Instance> Spi<'d, T, Async> { crate::dma::read(rx_ch, self.inner.regs().dr().ptr() as *const _, rx_ptr, T::RX_DREQ) }; join(tx_transfer, rx_transfer).await; + + // if tx > rx we should clear any overflow of the FIFO SPI buffer + if from_len > to_len { + let p = self.inner.regs(); + unsafe { + while p.sr().read().bsy() {} + + // clear RX FIFO contents to prevent stale reads + while p.sr().read().rne() { + let _: u16 = p.dr().read().data(); + } + // clear RX overrun interrupt + p.icr().write(|w| w.set_roric(true)); + } + } + Ok(()) } }