QUERY · ISSUE

[STM32] DTCM buffer incorrect sized for processor type

openby rolandvsopened 2018-10-14updated 2018-10-15

port-stm32

In flashbdev.clocation and below the used DTCM is 64kByte, however the STM32F76xxx and STM32F77xxx feature a DTCM of 128kByte, whereas the STM32F75xx and STM32F74xx have a 64kByte DTCM.

CANDIDATE · PULL REQUEST

ports/stm32: Make ETH DMA buffer attributes configurable.

closedby kwagyemanopened 2025-01-24updated 2025-02-04

port-stm32

This commit allows the attributes for the eth_dma buffer to be overridden by a port.

OpenMV's firmware for the Arduino Portenta stores .data in the DTCM which is inaccessible by the ethernet controller. By overriding the buffer's attributes with alignment and section specifications, we can place the ethernet buffer in the right SRAM location.

Assessment

Q Qwen · medium

Both items concern STM32 memory layout and DTCM usage, but they address different specific problems. Issue #4238 is about the flashbdev.c buffer being incorrectly sized (64k vs 128k) for different STM32F7 variants. PR #16633 is about making Ethernet DMA buffer attributes configurable to allow placement in DTCM when needed. While both involve DTCM and STM32, the PR does not fix the flashbdev buffer sizing issue described in the query. The PR addresses a different memory allocation problem (Ethernet DMA buffer placement) rather than the flashbdev buffer size mismatch.

Suggested action

Keep issue #4238 open as it addresses a distinct problem not resolved by PR #16633. The PR provides useful context about DTCM configuration but does not fix the flashbdev buffer sizing bug.

[STM32] DTCM buffer incorrect sized for processor type

ports/stm32: Make ETH DMA buffer attributes configurable.

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