[PATCH v3 2/6] nvme: assign of_node to nvme device

[Dragan Simic]

Hello all,

On 2024-08-06 15:03, Christian Marangi wrote:
> On Tue, Aug 06, 2024 at 02:43:12PM +0200, Christoph Hellwig wrote:
>> On Tue, Aug 06, 2024 at 01:41:12PM +0200, Christian Marangi wrote:
>> > Introduce support for a dedicated node for a nvme card. This will be a
>> > subnode of the nvme controller node that will have the "nvme-card"
>> > compatible.
>> >
>> > This follow a similar implementation done for mmc where the specific mmc
>> > card have a dedicated of_node.
>> >
>> > This can be used for scenario where block2mtd module is used to declare
>> > partition in DT and block2mtd is called on the root block of the nvme
>> > card, permitting the usage of fixed-partition parser or alternative
>> > ones.
>> 
>> Err, hell no.  Why would you wire up a purely PCIe device to OF?
>> PCIe is self-discovering.
>> 
> 
> Well on embedded pure PCIe card most of the time are not a thing...
> Unless it's an enterprise product, everything is integrated in the pcb
> and not detachable for cost saving measure or also if the thing use 
> PCIe
> protocol but it tighlty coupled with the SoC.
> 
> This implementation is already very common for all kind of pcie devices
> like wireless card, gpio expander that are integrated in the PCB and
> require property in DT like calibration data, quirks or GPIO pin
> definitions, i2c...
> 
> In modern SoC we are seeing an influx of using cheap flash storage
> option instead of NAND or NOR as modern hw require more space and price
> increase is not that high... Almost any high tier device is switching 
> to
> using emmc and even attached NVME and simulating MTD with them for easy
> usage.
> 
> Please consider this well used scenario in emebedded where PCIe is just
> a comunication way and the concept of detachable doesn't exist at all
> and things can be described in DT as static. Also these storage are 
> used
> for rootfs mount so userspace is not so viable.

As a note, perhaps this is another good example of a "fixed layout"
PCIe device found on an SBC:

https://lore.kernel.org/linux-rockchip/20240805073425.3492078-1-jacobe.zang@wesion.com/T/#u