[V9,1/2] dt-bindings: mailbox: add binding doc for the ARM SMC/HVC mailbox
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Message ID 1569377224-5755-2-git-send-email-peng.fan@nxp.com
State New
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Series
  • mailbox: arm: introduce smc triggered mailbox
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Commit Message

Peng Fan Sept. 25, 2019, 2:09 a.m. UTC
From: Peng Fan <peng.fan@nxp.com>

The ARM SMC/HVC mailbox binding describes a firmware interface to trigger
actions in software layers running in the EL2 or EL3 exception levels.
The term "ARM" here relates to the SMC instruction as part of the ARM
instruction set, not as a standard endorsed by ARM Ltd.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
---
 .../devicetree/bindings/mailbox/arm-smc.yaml       | 96 ++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.yaml

Comments

Andre Przywara Sept. 25, 2019, 5:09 p.m. UTC | #1
On Wed, 25 Sep 2019 02:09:08 +0000
Peng Fan <peng.fan@nxp.com> wrote:

Hi,

> From: Peng Fan <peng.fan@nxp.com>
> 
> The ARM SMC/HVC mailbox binding describes a firmware interface to trigger
> actions in software layers running in the EL2 or EL3 exception levels.
> The term "ARM" here relates to the SMC instruction as part of the ARM
> instruction set, not as a standard endorsed by ARM Ltd.
> 
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  .../devicetree/bindings/mailbox/arm-smc.yaml       | 96 ++++++++++++++++++++++
>  1 file changed, 96 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/arm-smc.yaml b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml
> new file mode 100644
> index 000000000000..b061954d1678
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml
> @@ -0,0 +1,96 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mailbox/arm-smc.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ARM SMC Mailbox Interface
> +
> +maintainers:
> +  - Peng Fan <peng.fan@nxp.com>
> +
> +description: |
> +  This mailbox uses the ARM smc (secure monitor call) or hvc (hypervisor
> +  call) instruction to trigger a mailbox-connected activity in firmware,
> +  executing on the very same core as the caller. The value of r0/w0/x0
> +  the firmware returns after the smc call is delivered as a received
> +  message to the mailbox framework, so synchronous communication can be
> +  established. The exact meaning of the action the mailbox triggers as
> +  well as the return value is defined by their users and is not subject
> +  to this binding.
> +
> +  One example use case of this mailbox is the SCMI interface, which uses
> +  shared memory to transfer commands and parameters, and a mailbox to
> +  trigger a function call. This allows SoCs without a separate management
> +  processor (or when such a processor is not available or used) to use
> +  this standardized interface anyway.
> +
> +  This binding describes no hardware, but establishes a firmware interface.
> +  Upon receiving an SMC using the described SMC function identifier, the
> +  firmware is expected to trigger some mailbox connected functionality.
> +  The communication follows the ARM SMC calling convention.
> +  Firmware expects an SMC function identifier in r0 or w0. The supported
> +  identifier are passed from consumers, or listed in the the arm,func-id

                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
		This is now obsolete.

The rest looks good to me, thanks for the changes!

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre.

> +  property as described below. The firmware can return one value in
> +  the first SMC result register, it is expected to be an error value,
> +  which shall be propagated to the mailbox client.
> +
> +  Any core which supports the SMC or HVC instruction can be used, as long
> +  as a firmware component running in EL3 or EL2 is handling these calls.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - description:
> +          For implementations using ARM SMC instruction.
> +        const: arm,smc-mbox
> +
> +      - description:
> +          For implementations using ARM HVC instruction.
> +        const: arm,hvc-mbox
> +
> +  "#mbox-cells":
> +    const: 0
> +
> +  arm,func-id:
> +    description: |
> +      An single 32-bit value specifying the function ID used by the mailbox.
> +      The function ID follows the ARM SMC calling convention standard.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
> +required:
> +  - compatible
> +  - "#mbox-cells"
> +  - arm,func-id
> +
> +examples:
> +  - |
> +    sram@93f000 {
> +      compatible = "mmio-sram";
> +      reg = <0x0 0x93f000 0x0 0x1000>;
> +      #address-cells = <1>;
> +      #size-cells = <1>;
> +      ranges = <0x0 0x93f000 0x1000>;
> +
> +      cpu_scp_lpri: scp-shmem@0 {
> +        compatible = "arm,scmi-shmem";
> +        reg = <0x0 0x200>;
> +      };
> +    };
> +
> +    smc_tx_mbox: tx_mbox {
> +      #mbox-cells = <0>;
> +      compatible = "arm,smc-mbox";
> +      arm,func-id = <0xc20000fe>;
> +    };
> +
> +    firmware {
> +      scmi {
> +        compatible = "arm,scmi";
> +        mboxes = <&smc_tx_mbox>;
> +        mbox-names = "tx";
> +        shmem = <&cpu_scp_lpri>;
> +      };
> +    };
> +
> +...
Peng Fan Sept. 26, 2019, 9:15 a.m. UTC | #2
Hi Andre,

> Subject: Re: [PATCH V9 1/2] dt-bindings: mailbox: add binding doc for the
> ARM SMC/HVC mailbox
> 
[...]
> > + supported  identifier are passed from consumers, or listed in the
> > + the arm,func-id
> 
>                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 		This is now obsolete.
> 
> The rest looks good to me, thanks for the changes!
> 
> Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Thanks, I'll wait to see whether Rob and Jassi has some comments or not.

Then post out v10 to address your comments.

Thanks,
Peng.

> 
> Cheers,
> Andre.
> 
> > +  property as described below. The firmware can return one value in
> > + the first SMC result register, it is expected to be an error value,
> > + which shall be propagated to the mailbox client.
> > +
> > +  Any core which supports the SMC or HVC instruction can be used, as
> > + long  as a firmware component running in EL3 or EL2 is handling these
> calls.
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - description:
> > +          For implementations using ARM SMC instruction.
> > +        const: arm,smc-mbox
> > +
> > +      - description:
> > +          For implementations using ARM HVC instruction.
> > +        const: arm,hvc-mbox
> > +
> > +  "#mbox-cells":
> > +    const: 0
> > +
> > +  arm,func-id:
> > +    description: |
> > +      An single 32-bit value specifying the function ID used by the
> mailbox.
> > +      The function ID follows the ARM SMC calling convention standard.
> > +    $ref: /schemas/types.yaml#/definitions/uint32
> > +
> > +required:
> > +  - compatible
> > +  - "#mbox-cells"
> > +  - arm,func-id
> > +
> > +examples:
> > +  - |
> > +    sram@93f000 {
> > +      compatible = "mmio-sram";
> > +      reg = <0x0 0x93f000 0x0 0x1000>;
> > +      #address-cells = <1>;
> > +      #size-cells = <1>;
> > +      ranges = <0x0 0x93f000 0x1000>;
> > +
> > +      cpu_scp_lpri: scp-shmem@0 {
> > +        compatible = "arm,scmi-shmem";
> > +        reg = <0x0 0x200>;
> > +      };
> > +    };
> > +
> > +    smc_tx_mbox: tx_mbox {
> > +      #mbox-cells = <0>;
> > +      compatible = "arm,smc-mbox";
> > +      arm,func-id = <0xc20000fe>;
> > +    };
> > +
> > +    firmware {
> > +      scmi {
> > +        compatible = "arm,scmi";
> > +        mboxes = <&smc_tx_mbox>;
> > +        mbox-names = "tx";
> > +        shmem = <&cpu_scp_lpri>;
> > +      };
> > +    };
> > +
> > +...
Rob Herring Sept. 27, 2019, 2:46 p.m. UTC | #3
On Wed, 25 Sep 2019 02:09:08 +0000, Peng Fan wrote:
> From: Peng Fan <peng.fan@nxp.com>
>
> The ARM SMC/HVC mailbox binding describes a firmware interface to trigger
> actions in software layers running in the EL2 or EL3 exception levels.
> The term "ARM" here relates to the SMC instruction as part of the ARM
> instruction set, not as a standard endorsed by ARM Ltd.
>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> ---
>  .../devicetree/bindings/mailbox/arm-smc.yaml       | 96 ++++++++++++++++++++++
>  1 file changed, 96 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/arm-smc.yaml
>

Reviewed-by: Rob Herring <robh@kernel.org>

Patch
diff mbox series

diff --git a/Documentation/devicetree/bindings/mailbox/arm-smc.yaml b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml
new file mode 100644
index 000000000000..b061954d1678
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/arm-smc.yaml
@@ -0,0 +1,96 @@ 
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/mailbox/arm-smc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ARM SMC Mailbox Interface
+
+maintainers:
+  - Peng Fan <peng.fan@nxp.com>
+
+description: |
+  This mailbox uses the ARM smc (secure monitor call) or hvc (hypervisor
+  call) instruction to trigger a mailbox-connected activity in firmware,
+  executing on the very same core as the caller. The value of r0/w0/x0
+  the firmware returns after the smc call is delivered as a received
+  message to the mailbox framework, so synchronous communication can be
+  established. The exact meaning of the action the mailbox triggers as
+  well as the return value is defined by their users and is not subject
+  to this binding.
+
+  One example use case of this mailbox is the SCMI interface, which uses
+  shared memory to transfer commands and parameters, and a mailbox to
+  trigger a function call. This allows SoCs without a separate management
+  processor (or when such a processor is not available or used) to use
+  this standardized interface anyway.
+
+  This binding describes no hardware, but establishes a firmware interface.
+  Upon receiving an SMC using the described SMC function identifier, the
+  firmware is expected to trigger some mailbox connected functionality.
+  The communication follows the ARM SMC calling convention.
+  Firmware expects an SMC function identifier in r0 or w0. The supported
+  identifier are passed from consumers, or listed in the the arm,func-id
+  property as described below. The firmware can return one value in
+  the first SMC result register, it is expected to be an error value,
+  which shall be propagated to the mailbox client.
+
+  Any core which supports the SMC or HVC instruction can be used, as long
+  as a firmware component running in EL3 or EL2 is handling these calls.
+
+properties:
+  compatible:
+    oneOf:
+      - description:
+          For implementations using ARM SMC instruction.
+        const: arm,smc-mbox
+
+      - description:
+          For implementations using ARM HVC instruction.
+        const: arm,hvc-mbox
+
+  "#mbox-cells":
+    const: 0
+
+  arm,func-id:
+    description: |
+      An single 32-bit value specifying the function ID used by the mailbox.
+      The function ID follows the ARM SMC calling convention standard.
+    $ref: /schemas/types.yaml#/definitions/uint32
+
+required:
+  - compatible
+  - "#mbox-cells"
+  - arm,func-id
+
+examples:
+  - |
+    sram@93f000 {
+      compatible = "mmio-sram";
+      reg = <0x0 0x93f000 0x0 0x1000>;
+      #address-cells = <1>;
+      #size-cells = <1>;
+      ranges = <0x0 0x93f000 0x1000>;
+
+      cpu_scp_lpri: scp-shmem@0 {
+        compatible = "arm,scmi-shmem";
+        reg = <0x0 0x200>;
+      };
+    };
+
+    smc_tx_mbox: tx_mbox {
+      #mbox-cells = <0>;
+      compatible = "arm,smc-mbox";
+      arm,func-id = <0xc20000fe>;
+    };
+
+    firmware {
+      scmi {
+        compatible = "arm,scmi";
+        mboxes = <&smc_tx_mbox>;
+        mbox-names = "tx";
+        shmem = <&cpu_scp_lpri>;
+      };
+    };
+
+...