Re: [RFC 1/4] arm64: amd-seattle: Adding device tree for AMD Seattle platform

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On 10/10/2014 8:45 AM, Mark Rutland wrote:
Hi Suravee,

On Sun, Sep 28, 2014 at 09:53:27PM +0100, suravee.suthikulpanit@xxxxxxx wrote:
From: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>

Initial revision of device tree for AMD Seattle platform

To check: how is it possible to make use of a DTB generated from this
dts? Can a user update the DTB used by the Seattle firmware?

In the current FW, there is a mechanism that users can modify and provide UEFI with the updated device tree to override the one that comes with Seattle firmware.

[...];
+
+       timer@1,1060000 {
+               compatible = "arm,standalone_a5_twd";
+               reg = <0 0x1060000 0 0x40>;
+               interrupts =
+                       <0 378 4>,
+                       <0 379 4>;
+       };

This binding does not exist in mainline.

I am removing this.


+
+       ccp: ccp@1,00100000 {
+               compatible = "amd,ccp-seattle-v1a";
+               reg = <0 0x00100000 0 0x10000>;
+               interrupts = <0 3 4>;
+               dma-coherent;
+       };

Nor does this.

The binding for this one is here (http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/crypto/amd-ccp.txt).


> [....]

+               linux,pci-probe-only;

Why is this necessary?

This was defined in the PCI Generic Host Controller binding here (http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/pci/host-generic-pci.txt).


+       };
+
+       aliases {
+               serial0 = &v2m_serial0;
+       };
+
+       /* Note: This entry is modified by UEFI */

In what way is this modified?

1. UEFI would basically take out certain CPUs and modify the cpu-map accordingly.
2. Change method to psci-0.2 when support is in place.
3. Update release address.

Actually, the "cpus" entry should/will be fully auto generated by UEFI in the future BIOS. I think I'll be taking this out completely for now.

[...]

+
+       /* Note: This entry is modified by UEFI */
+       memory@8000000000 {
+               device_type = "memory";
+               reg = <0x00000080 0x00000000 0x1 0x00000000>; /* 4GB */
+       };

Why does UEFI modify this? When booted via UEFI we use the UEFI memory
map.

True. But for non-EFI boot (as fallback), we still need this. UEFI will update the amount of detected memory.

Actually, same here as the "cpus", this entry should/will go away completely from the static DT, and UEFI will auto-generate this in the future firmware.

Thanks,

Suravee
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