Subject: Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc for the ARM
SMC/HVC mailbox

On Fri, Aug 30, 2019 at 2:37 AM Peng Fan [off-list ref] wrote:

quoted

Hi Jassi,

quoted

Subject: Re: [PATCH v5 1/2] dt-bindings: mailbox: add binding doc
for the ARM SMC/HVC mailbox

On Fri, Aug 30, 2019 at 1:28 AM Peng Fan [off-list ref] wrote:

quoted

quoted

quoted

+examples:
+  - |
+    sram@910000 {
+      compatible = "mmio-sram";
+      reg = <0x0 0x93f000 0x0 0x1000>;
+      #address-cells = <1>;
+      #size-cells = <1>;
+      ranges = <0 0x0 0x93f000 0x1000>;
+
+      cpu_scp_lpri: scp-shmem@0 {
+        compatible = "arm,scmi-shmem";
+        reg = <0x0 0x200>;
+      };
+
+      cpu_scp_hpri: scp-shmem@200 {
+        compatible = "arm,scmi-shmem";
+        reg = <0x200 0x200>;
+      };
+    };
+
+    firmware {
+      smc_mbox: mailbox {
+        #mbox-cells = <1>;
+        compatible = "arm,smc-mbox";
+        method = "smc";
+        arm,num-chans = <0x2>;
+        transports = "mem";
+        /* Optional */
+        arm,func-ids = <0xc20000fe>, <0xc20000ff>;

SMC/HVC is synchronously(block) running in "secure mode", i.e,
there can only be one instance running platform wide. Right?

I think there could be channel for TEE, and channel for Linux.
For virtualization case, there could be dedicated channel for each VM.

I am talking from Linux pov. Functions 0xfe and 0xff above, can't
both be active at the same time, right?

If I get your point correctly,
On UP, both could not be active. On SMP, tx/rx could be both active,
anyway this depends on secure firmware and Linux firmware design.

Do you have any suggestions about arm,func-ids here?

I was thinking if this is just an instruction, why can't each channel be
represented as a controller, i.e, have exactly one func-id per controller node.
Define as many controllers as you need channels ?

I am ok, this could make driver code simpler. Something as below?

    smc_tx_mbox: tx_mbox {
      #mbox-cells = <0>;
      compatible = "arm,smc-mbox";
      method = "smc";
      transports = "mem";
      arm,func-id = <0xc20000fe>;
    };

    smc_rx_mbox: rx_mbox {
      #mbox-cells = <0>;
      compatible = "arm,smc-mbox";
      method = "smc";
      transports = "mem";
      arm,func-id = <0xc20000ff>;
    };

    firmware {
      scmi {
        compatible = "arm,scmi";
        mboxes = <&smc_tx_mbox>, <&smc_rx_mbox 1>;
        mbox-names = "tx", "rx";
        shmem = <&cpu_scp_lpri>, <&cpu_scp_hpri>;
      };
    };

Thanks,
Peng.

-j

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