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Fix EasyDMA max size. #315

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May 11, 2021
Merged

Fix EasyDMA max size. #315

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44 changes: 25 additions & 19 deletions nrf-hal-common/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,29 +92,35 @@ pub mod prelude {
}

/// Length of Nordic EasyDMA differs for MCUs
#[cfg(any(
feature = "52810",
feature = "52811",
feature = "52832",
feature = "51"
))]
pub mod target_constants {
// NRF52832 8 bits1..0xFF
pub const EASY_DMA_SIZE: usize = 255;
// Easy DMA can only read from data ram
pub const SRAM_LOWER: usize = 0x2000_0000;
pub const SRAM_UPPER: usize = 0x3000_0000;
pub const FORCE_COPY_BUFFER_SIZE: usize = 255;
const _CHECK_FORCE_COPY_BUFFER_SIZE: usize = EASY_DMA_SIZE - FORCE_COPY_BUFFER_SIZE;
// ERROR: FORCE_COPY_BUFFER_SIZE must be <= EASY_DMA_SIZE
}
#[cfg(any(feature = "52840", feature = "52833", feature = "9160"))]
pub mod target_constants {
// NRF52840 and NRF9160 16 bits 1..0xFFFF
pub const EASY_DMA_SIZE: usize = 65535;
#[cfg(feature = "51")]
pub const EASY_DMA_SIZE: usize = (1 << 8) - 1;
#[cfg(feature = "52805")]
pub const EASY_DMA_SIZE: usize = (1 << 14) - 1;
#[cfg(feature = "52810")]
pub const EASY_DMA_SIZE: usize = (1 << 10) - 1;
#[cfg(feature = "52811")]
pub const EASY_DMA_SIZE: usize = (1 << 14) - 1;
#[cfg(feature = "52820")]
pub const EASY_DMA_SIZE: usize = (1 << 15) - 1;
#[cfg(feature = "52832")]
pub const EASY_DMA_SIZE: usize = (1 << 8) - 1;
#[cfg(feature = "52833")]
pub const EASY_DMA_SIZE: usize = (1 << 16) - 1;
#[cfg(feature = "52840")]
pub const EASY_DMA_SIZE: usize = (1 << 16) - 1;
#[cfg(feature = "5340")]
pub const EASY_DMA_SIZE: usize = (1 << 16) - 1;
#[cfg(feature = "9160")]
pub const EASY_DMA_SIZE: usize = (1 << 12) - 1;

// Limits for Easy DMA - it can only read from data ram
pub const SRAM_LOWER: usize = 0x2000_0000;
pub const SRAM_UPPER: usize = 0x3000_0000;

#[cfg(any(feature = "51", feature = "52810", feature = "52832"))]
pub const FORCE_COPY_BUFFER_SIZE: usize = 255;
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Do we even need this constant if we already have EASY_DMA_SIZE?

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I would say it's not necessarily bad to have a smaller force copy buffer size than the maximum allowed by DMA, because it gives less side effects with too big buffers overflowing memory unintentionally.

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Yeah, stack-allocating a 64kb copy buffer wouldn't be pretty

#[cfg(not(any(feature = "51", feature = "52810", feature = "52832")))]
pub const FORCE_COPY_BUFFER_SIZE: usize = 1024;
const _CHECK_FORCE_COPY_BUFFER_SIZE: usize = EASY_DMA_SIZE - FORCE_COPY_BUFFER_SIZE;
// ERROR: FORCE_COPY_BUFFER_SIZE must be <= EASY_DMA_SIZE
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