spi@0 { ... flash@0 { compatible = "jedec,spi-nor" reg = <0x00>; stacked-memories = <&flash@0 &flash@1>; spi-max-frequency = <50000000>; ... partitions { compatible = "fixed-partitions"; concat-partition = <&flash0_part0 &flash1_part0>;
flash0_part0: partition@0 { label = "part0_0"; reg = <0x0 0x800000>; }; };}; flash@1 { compatible = "jedec,spi-nor" reg = <0x01>; stacked-memories = <&flash@0 &flash@1>; spi-max-frequency = <50000000>; ... partitions { compatible = "fixed-partitions"; concat-partition = <&flash0_part0 &flash1_part0>;
flash1_part0: partition@0 { label = "part0_1"; reg = <0x0 0x800000>; }; };}; };
compatible = "fixed-partitions"; concat-partition = <&flash0_partition &flash1_partition>; flash1_partition: partition@0 { label = "part0_1"; reg = <0x0 0x800000>; } } }}
parallel-memories binding changes:
- Remove the size information from the bindings and change the type to boolen.
- Each flash connected in parallel mode should be identical and will have one flash node for both the flash devices.
- The “reg” prop will contain the physical CS number for both the connected flashes.
The new layer will double the mtd-> size and register it with the mtd layer.
Not so sure about that, you'll need a new mtd device to capture the whole
device.
But this is implementation related, not relevant for binding.
spi@1 { ... flash@3 { compatible = "jedec,spi-nor" reg = <0x00 0x01>; paralle-memories ;
Please fix the typos and the spacing (same above).
spi-max-frequency = <50000000>; ... partitions { compatible = "fixed-partitions"; flash0_partition: partition@0 { label = "part0_0"; reg = <0x0 0x800000>; } } }}
Signed-off-by: Amit Kumar Mahapatra amit.kumar-mahapatra@amd.com
.../bindings/spi/spi-controller.yaml | 23 +++++++++++++++++-- .../bindings/spi/spi-peripheral-props.yaml | 9 +++----- 2 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/Documentation/devicetree/bindings/spi/spi-controller.yaml b/Documentation/devicetree/bindings/spi/spi-controller.yaml index 093150c0cb87..2d300f98dd72 100644 --- a/Documentation/devicetree/bindings/spi/spi-controller.yaml +++ b/Documentation/devicetree/bindings/spi/spi-controller.yaml @@ -185,7 +185,26 @@ examples: flash@2 { compatible = "jedec,spi-nor"; spi-max-frequency = <50000000>;
reg = <2>, <3>;stacked-memories = /bits/ 64 <0x10000000 0x10000000>;
reg = <2>;stacked-memories = <&flash0 &flash1>; };I'm sorry but this is not what you've talked about in this series. Either you have flash0 and flash1 and use the stacked-memories property in both of them (which is what you described) or you create a third virtual device which points to two other flashes. This example allows for an easier use of the partitions
If I understand your point correctly, you're suggesting that we should avoid using stacked-memories and concat-partition properties together and instead choose one approach. Between the two, I believe concat-partition would be the better option.
That's not exactly it, look at the reg properties above, they do not match the flash devices. Your example above invalid but it is not clear whether this is another typo or voluntary.
Ah, I see. It's a typo ☹. However, based on the discussion below, it seems we might not need the 'stacked-memories' property anymore.
While looking into your mtdconcat patch [1], I noticed that it creates a virtual MTD device that points to partitions on two different flash nodes, which aligns perfectly with our requirements.
However, there are two key concerns that, if addressed, could make this patch suitable for the stacked mode:
1/ The creation of a virtual device that does not have a physical existence.
We do already have:
- the master mtd device (disabled by default for historical reasons, but can be enabled with a Kconfig option).
- an mtd device per partition
I don't see a problem in creating virtual mtd devices in the kernel.
2/ The creation of individual MTD devices that are concatenated to form the virtual MTD device, which may not be needed by the user.
You can also get rid of them by default (or perhaps do the opposite and let a Kconfig option for that).
Ok, great! I'll look into it and try to integrate it into your previous patch [1]. If everything works out, then IMHO this(patch[1] + the above changes) should suffice for adding stacked support.
Regards, Amit
Regarding the first point, I currently cannot think of a better generic way to support the stacked feature than creating a virtual device. Please let me know you thoughts on this.
For the second point, one possible solution is to hide the individual MTD devices (that form the concatenated virtual MTD device) from the user once the virtual device is created. Please let us know if you have any other suggestions to address this issue.
That is what is done with the master device by default.
[1] https://lore.kernel.org/linux-mtd/20191127105522.31445-5-miquel.raynal @bootlin.com/
Thanks, Miquèl