On Fri, 21 Mar 2025 at 12:47, Javier Casas Marin
<javierca...@geotab.com.invalid> wrote:
> Hi,
> We are using the FTL driver over a MTD device (flash memory at45db641e).
> When we write something to flash, eventually the ftl_flush function is
> called and it does an erase (MTD_ERASE) and then the write (MTD_BWRITE).
> But in the at45db driver (at45db.c) the write uses command 0x82 ("Main
> Memory Page Program through Buffer 1 with Built-In Erase") that also
> performs a built-in erase before the write. In summary, each time we write
> to flash, the page is erased twice before it is written, first in the FTL
> driver and then in the MTD driver.
>
> The at45db device has another command that doesn't include the built-in
> erase prior to the write: "Main Memory Byte/Page Program through Buffer 1
> without Built-In Erase" (0x02) that is not present in the current version
> of the driver. Several questions here:
>
> 1. Is it expected that a write to a flash MTD device can fail without
> erasing? In this case, the responsibility for erasing the page belongs to
> upper layers and the MTD driver doesn't have to perform the erase before
> the write (-> move to use command 0x02 instead of the one currently used,
> 0x82).
>
The problem is your chip and not the driver :)
The at45db driver was written for the AT45DB161D.
Opcode 82H = Main Memory Page Program Through Buffer 1
For your chip (at45db641e)
Opcode 82H = Main Memory Page Program through Buffer 1 with Built-In Erase
Opcode 02H = Main Memory Byte/Page Program through Buffer 1 without
Built-In Erase
