Provide more information about RAM from the bootloader about devicetree-specification HOT 6 OPEN

I think this duplicates a bit Documentation/devicetree/bindings/memory-controllers/ddr/ in Linux kernel. We already describe memory under memory controllers. I guess the top level memory is only for parsing size/location for FW/OS.

from devicetree-specification.

@krzk Generally I'd agree with you. The problem is:

• This property has unfortunately already been used by the existing Qualcomm bootloaders,
• Several bits in the GPU and display drivers should take DDR type into account when programming registers

I hate to ask this, but is there a chance to receive a pardon for this property, provided it is limited to Qualcomm platorms?

from devicetree-specification.

Go look at 'lshw'. It already supports some similar properties in the memory nodes dating back to PowerMac days.

from devicetree-specification.

@robherring I'm not sure if you comment is 'pro' or 'contra', could you please be more specific?

from devicetree-specification.

I'm saying if what's supported by lshw works for you, then I'd be open to supporting it.

However, note that with UEFI boot, there are no memory nodes...

from devicetree-specification.

@robherring no, they are not supported by lshw.

We are currently in the following position: the existing bootloader writes this DT property. While we potentially can try persuading Qualcomm to use correct DT entry (no guarantees on the result though), existing devices are already ddr_device_type. The bootloader is cryptographically signed by the device vendor, so updating old them on existing hardware is close to being impossible.

Parsing this DDR memory type becomes important for the display and GPU drivers to properly setup the hardware. Thus we are asking for an "exception": we'd like to document the mentioned /memory@[something]/ddr_device_type for Qualcomm devices and use this DT property.

from devicetree-specification.