[HELP] STM32 Standardized Flash Terminology

[stbenn]

Description

I will limit this discussion to STM32 architecture, as I am not familiar with other architectures.

I have been working on a progmem flash driver for the STM32H5, and noticed inconsistent terminology for "block" and "page" across other STM32 driver implementations (mainly stm32h743xx_flash.c and arch/arm/src/stm32u5/stm32_flash.c).

A quick google search for the generally accepted meanings:

• Block = smallest unit of flash that can be erased.
• Page = smallest unit that can be programmed (written)

The H7 driver appears to mostly adhere to the generally accepted meanings, but the U5 uses "page" to refer to what is actually a block, and does not implement pages (referring to smallest unit that can be programmed).

Additionally, drivers/mtd/mtd_progmem.c::progmem_bwrite() appears to use "block" to refer to pages.

Am I misunderstanding the implementations or am I correct that there doesn't seem to be consistent usage of "block" and "page"?

I want to make sure I understand this before creating a PR for the H5 driver so I don't add to the problem (if there is one)!

Verification

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[Laczen]

@stbenn the terminology used in flash devices can indeed be confusing. The term block is especially confusing, I would advice against using it (the same for page). The most clear definition I have found up to now are:

• Erase-block: the smallest size to erase, this is sometimes also referred to as sector.
• Write-block: the smallest size to write, this is used by bwrite,
• Page: the largest size that can be written in one operation, typically for external flash that have a page buffer.

The most important thing is not to think the block used in bwrite as being the same block used in erase.

It is difficult to standardize because the author of a driver might use the terminology used in the device datasheet or manual.

[stbenn]

It is difficult to standardize because the author of a driver might use the terminology used in the device datasheet or manual.

I am sure this is at least a large source of the inconsistency in the STM chips I have noticed.

• RM0456 for STM32U5: Erase blocks are called "pages"
• RM0481 for STM32H5: Erase blocks are called "sectors"
• RM0399 for STM32H7: Erase blocks are called "sectors"