Hi, Miquel, On 12/6/21 11:59 AM, Miquel Raynal wrote: > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe > > The Xilinx QSPI controller has two advanced modes which allow the > controller to behave differently and consider two flashes as one single > storage. > > One of these two modes is quite complex to support from a binding point > of view and is the dual parallel memories. In this mode, each byte of > data is stored in both devices: the even bits in one, the odd bits in > the other. The split is automatically handled by the QSPI controller and > is transparent for the user. > > The other mode is simpler to support, it is called dual stacked > memories. The controller shares the same SPI bus but each of the devices > contain half of the data. Once in this mode, the controller does not > follow CS requests but instead internally wires the two CS levels with > the value of the most significant address bit. The stacked mode that you describe seems particular to a specific vendor. There are multi die NOR flashes which do not require any controller intervention, the logic is held at the flash level: https://media-www.micron.com/-/media/client/global/documents/products/technical-note/nor-flash/tn2505_n25q_mt25q_stacked_devices.pdf?rev=7a23cc95238e46f7b22e2a9f6bc736b7 Can you point us to which kind of memories you're willing to add support for? Some datasheets will be best. Cheers, ta > > Supporting these two modes will involve core changes which include the > possibility of providing two CS for a single SPI device > > Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx> > Acked-by: Rob Herring <robh@xxxxxxxxxx> > --- > Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > index 39421f7233e4..4abfb4cfc157 100644 > --- a/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > +++ b/Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml > @@ -47,7 +47,8 @@ properties: > identified by the JEDEC READ ID opcode (0x9F). > > reg: > - maxItems: 1 > + minItems: 1 > + maxItems: 2 > > spi-max-frequency: true > spi-rx-bus-width: true > -- > 2.27.0 >
