Re: [Qemu-block] [PATCH v3 04/10] block/pflash_cfi02: Implement intereleaved flash devices

[Thomas Huth]

On 18/04/2019 00.01, Stephen Checkoway wrote:
> It's common for multiple narrow flash chips to be hooked up in parallel
> to support wider buses. For example, four 8-bit wide flash chips (x8)
> may be combined in parallel to produce a 32-bit wide device. Similarly,
> two 16-bit wide chips (x16) may be combined.
> 
> This commit introduces `device-width` and `max-device-width` properties,
> similar to pflash_cfi01, with the following meanings:
> - `width`: The width of the logical, qemu device (same as before);
> - `device-width`: The width of an individual flash chip, defaulting to
>   `width`; and
> - `max-device-width`: The maximum width of an individual flash chip,
>   defaulting to `device-width`.
> 
> Nothing needs to change to support reading such interleaved devices but
> commands (e.g., erase and programming) must be sent to all devices at
> the same time or else the various chips will be in different states.
> 
> For example, a 4-byte wide logical device can be composed of four x8/x16
> devices in x8 mode. That is, each device supports both x8 or x16 and
> they're being used in the byte, rather than word, mode. This
> configuration would have `width=4`, `device-width=1`, and
> `max-device-width=2`.
> 
> In addition to commands being sent to all devices, guest firmware
> expects the status and CFI queries to be replicated for each device.
> (The one exception to the response replication is that each device gets
> to report its own status bit DQ7 while programming because its value
> depends on the value being programmed which will usually differ for each
> device.)
> 
> Testing is limited to 16-bit wide devices due to the current inability
> to override the properties set by `pflash_cfi02_register`, but multiple
> configurations are tested.
> 
> Stop using global_qtest. Instead, package the qtest variable inside the
> FlashConfig structure.

Thanks for doing that change wrt global_qtest!

Acked-by: Thomas Huth <address@hidden>