[RFC PATCH 0/2] Add support for stacked and parallel memories

[Enrico Weigelt, metux IT consult]

On 26.10.24 09:53, Amit Kumar Mahapatra wrote:

Hi,


<snip>

> 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 help for protecting from a broken boot flash ?


--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info at metux.net -- +49-151-27565287