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tosc-rs / mnemos

An Operating System for Building Small Computers
https://mnemos.dev
Apache License 2.0
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feat(D1): add builders for DMAC descriptors #284

Closed hawkw closed 10 months ago

hawkw commented 10 months ago

Currently, the DMAC descriptor configuration fields are bit-packed every time a descriptor is constructed. However, the drivers which use DMA always construct descriptors with the same configuration bitfields -- only the addresses and lengths change. We can make this more efficient by constructing the config field once and copying it into each new descriptor.

This branch replaces the existing DescriptorConfig struct with a DescriptorBuilder, which is basically the same thing except it actually constructs the bitfield as a single u32. I used mycelium-bitfield to do this --- mostly for fun, but it's maybe a bit more readable than the previous code? I dunno.

hawkw commented 10 months ago

hmm, apparently something on this branch is actually making display updates way laggier than on main. gotta figure out what i did wrong!

hawkw commented 10 months ago

hmm, apparently something on this branch is actually making display updates way laggier than on main. gotta figure out what i did wrong!

Update on this: it was because i accidentally changed the DestDrqType for the SPI DMA transfers to Uart0Tx, which meant that the SPI sender wasn't getting woken when it was supposed to: https://github.com/tosc-rs/mnemos/pull/284/commits/5f948674f67825d4af37b1f6fd222b474f8c035c#diff-a1c995e700c35a1d06d5b9dff0ad6c866aa593007816181749bf218c6c69444aR129

I've fixed that and now everything is nice and snappy.