Add stacked and parallel memories support in spi-nor
Miquel Raynal
miquel.raynal at bootlin.com
Thu Oct 10 08:00:36 PDT 2024
Hi Amit,
amit.kumar-mahapatra at amd.com wrote on Thu, 10 Oct 2024 10:35:06 +0000:
> Hello Miquel,
>
> > -----Original Message-----
> > From: Miquel Raynal <miquel.raynal at bootlin.com>
> > Sent: Thursday, October 10, 2024 2:58 PM
> > To: Mahapatra, Amit Kumar <amit.kumar-mahapatra at amd.com>
> > Cc: Tudor Ambarus <tudor.ambarus at linaro.org>; michael at walle.cc;
> > broonie at kernel.org; pratyush at kernel.org; richard at nod.at; vigneshr at ti.com; Rob
> > Herring <robh at kernel.org>; cornor+dt at kernel.org; krzk+dt at kernel.org; linux-
> > spi at vger.kernel.org; linux-kernel at vger.kernel.org; linux-mtd at lists.infradead.org;
> > nicolas.ferre at microchip.com; alexandre.belloni at bootlin.com;
> > claudiu.beznea at tuxon.dev; Simek, Michal <michal.simek at amd.com>; linux-arm-
> > kernel at lists.infradead.org; alsa-devel at alsa-project.org;
> > patches at opensource.cirrus.com; linux-sound at vger.kernel.org; git (AMD-Xilinx)
> > <git at amd.com>; amitrkcian2002 at gmail.com; Conor Dooley
> > <conor.dooley at microchip.com>; beanhuo at micron.com
> > Subject: Re: Add stacked and parallel memories support in spi-nor
> >
> > Hi Amit,
> >
> > amit.kumar-mahapatra at amd.com wrote on Thu, 10 Oct 2024 09:17:58 +0000:
> >
> > > Hello Miquel,
> > >
> > > > > - The stacked-memories DT bindings will contain the phandles of
> > > > > the flash nodes
> > > > connected in stacked mode.
> > > > >
> > > > > - The first flash node will contain the mtd partition that would
> > > > > have the cross over memory staring at a memory location in the
> > > > > first flash and ending at some memory location of the 2nd flash
> > > >
> > > > I don't like that much. Describing partitions past the actual device
> > > > sounds wrong. If you look into [1] there is a suggestion from Rob to
> > > > handle this case using a property that tells us there is a
> > > > continuation, so from a software perspective we can easily make the link, but on
> > the hardware description side the information are correct.
> > >
> > > I reviewed Rob's suggestions in [1], and I need to examine the MTD
> > > layer to determine how this can be implemented from a software perspective.
> > > For reference, here is Rob's suggestion:
> > >
> > > Describe each device and partition separately and add link(s) from one
> > > partition to the next
> > >
> > > flash0 {
> > > partitions {
> > > compatible = "fixed-partitions";
> > > concat-partition = <&flash1_partitions>;
> > > ...
> > > };
> > > };
> > >
> > > flash1 {
> > > flash1_partition: partitions {
> > > compatible = "fixed-partitions";
> > > ...
> > > };
> > > };
> > >
> > > >
> > > > If this description is accepted, then fine, you can deprecate the "stacked-
> > memories"
> > > > property.
> > >
> > > I believe that in addition to Rob's description, we should also
> > > include the 'stacked-memories' property. This property helps us
> > > identify which flashes are stacked, while Rob's suggestion explains
> > > how the partitions within the stacked flashes are connected.
> > >
> > > For example, if we have three flashes connected to an SPI host, with
> > > flash at 0 and flash at 1 operating in stacked mode and flash at 2 functioning
> > > as a standalone flash, the Device Tree binding might look something like this:
> > > Please share your thoughts on this.
> > >
> > > spi at 0 {
> > > ...
> > > flash at 0 {
> > > compatible = "jedec,spi-nor"
> > > reg = <0x00>;
> > > stacked-memories = <&flash at 0 &flash at 1>;
> > > spi-max-frequency = <50000000>;
> > > ...
> > > flash0_partition: partitions {
> > > compatible = "fixed-partitions";
> > > concat-partition = <&flash1_partitions>;
> > > partition at 0 {
> > > label = "Stacked-Flash-1";
> > > reg = <0x0 0x800000>;
> > > }
> > > }
> > > }
> > > flash at 1 {
> > > compatible = "jedec,spi-nor"
> > > reg = <0x01>;
> > > spi-max-frequency = <50000000>;
> > > ...
> > > flash1_partition: partitions {
> > > compatible = "fixed-partitions";
> > > concat-partition = <&flash0_partitions>;
> > > partition at 0 {
> > > label = " Stacked-Flash-2";
> > > reg = <0x0 0x800000>;
> > > }
> > > }
> > > }
> > >
> > > flash at 2 {
> > > compatible = "jedec,spi-nor"
> > > reg = <0x01>;
> > > spi-max-frequency = <50000000>;
> > > ...
> > > partitions {
> > > compatible = "fixed-partitions";
> > > concat-partition = <&flash0_partitions>;
> > > partition at 0 {
> > > label = "Single-Flash";
> > > reg = <0x0 0x800000>;
> > > }
> > > }
> > > }
> >
> > I'm sorry but this is pretty messed up. The alignments are wrong, I believe the labels
> > are wrong, the reg properties as well. Can you please work on this example and
> > send an updated version?
>
> Apologies for that. Here's the updated version along with the explanation.
Thanks for the update.
> spi at 0 {
> ...
> flash at 0 {
> compatible = "jedec,spi-nor"
> reg = <0x00>;
> stacked-memories = <&flash at 0 &flash at 1>;
The same property should, IMHO, also be expected...
> spi-max-frequency = <50000000>;
> ...
> partitions {
> compatible = "fixed-partitions";
> concat-partition = <&flash1_partition>; /* Link to the flash at 1 partition at 0 */
> flash0_partition: partition at 0 {
> label = "part0_0";
> reg = <0x0 0x800000>;
> }
> }
> }
> flash at 1 {
> compatible = "jedec,spi-nor"
> reg = <0x01>;
... here.
> spi-max-frequency = <50000000>;
> ...
> partitions {
> compatible = "fixed-partitions";
> concat-partition = <&flash0_partition>; /* Link to the flash at 0 partition at 0 */
> flash1_partition: partition at 0 {
> label = "part0_1";
> reg = <0x0 0x800000>;
> }
> }
> }
>
> flash at 2 {
> compatible = "jedec,spi-nor"
> reg = <0x02>;
> spi-max-frequency = <50000000>;
> ...
> partitions {
> compatible = "fixed-partitions";
> partition at 0 {
> label = "part1_0";
> reg = <0x0 0x800000>;
> }
> }
> }
> }
Otherwise, okay for me.
Thanks,
Miquèl
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