Hello,
Stacked: Flashes share the same SPI bus, but different CS line, controller driver asserts the CS of the flash to which it needs to communicate. Stacked mode is a software abstraction rather than a controller feature or
capability.
At any given time, the controller communicates with one of the two connected flash devices, as determined by the requested address and data length. If an operation starts on one flash and ends on the other, the core needs to split it into two separate operations and adjust the data length accordingly.
Parallel(Multi-CS): Both the flashes have their separate SPI bus, CS of both the flashes will be asserted/de-asserted at the same time. In this mode data will be split across both the flashes by enabling the STRIPE setting in the controller. Parallel mode is a controller feature where if the STRIPE bit is set then the controller internally handles the data split during data write to the flashes and while reading data from the flash the controller internally merges data from both the flashes before writing to the
controller FIFO.
If STRIPE is not enabled, then same data will be sent to both the devices. In parallel mode both the flashes should be identical.
Interesting.
What's the practical use case ? Some kind of RAID directly on raw flashes ? Could it
In a parallel configuration, the user can double the flash capacity and data throughput.
Users disable STRIPE when they need to access the flash device registers for reading or writing.
help for protecting from a broken boot flash ?
No, because each read/write operation communicates with both flash devices simultaneously, meaning the image will be distributed across both flashes and read from both during boot.
Regards, Amit
--mtx
--
Hinweis: unverschlüsselte E-Mails können leicht abgehört und manipuliert werden ! Für eine vertrauliche Kommunikation senden Sie bitte ihren GPG/PGP-Schlüssel zu.
Enrico Weigelt, metux IT consult Free software and Linux embedded engineering info@metux.net -- +49-151- 27565287