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Message-ID: <f6f317d9-830d-4c38-998f-b229b3d9f95a@linaro.org>
Date: Thu, 14 Mar 2024 14:20:38 +0000
From: Caleb Connolly <caleb.connolly@...aro.org>
To: Amrit Anand <quic_amrianan@...cinc.com>, robh@...nel.org,
krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, agross@...nel.org,
andersson@...nel.org, konrad.dybcio@...aro.org
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-msm@...r.kernel.org, kernel@...cinc.com, peter.griffin@...aro.org,
linux-riscv@...ts.infradead.org, chrome-platform@...ts.linux.dev,
linux-mediatek@...ts.infradead.org, Simon Glass <sjg@...omium.org>
Subject: Re: [PATCH v2 2/2] dt-bindings: qcom: Update DT bindings for multiple
DT
Hi Amrit,
On 14/03/2024 12:11, Amrit Anand wrote:
> Qualcomm produces a lot of "unique" boards with slight differences in
> SoC's and board's configuration. For eg, there can be SM8150v1 on MTPv1,
> SM8150v1 on MTPv2, SM8150v2 on MTPv2, SM8150v2 on MTPv2 with a different
> PMIC, SM8150v2 with no modem support and so on. For instance, suppose we
> have 3 SoC, each with 4 boards supported, along with 2 PMIC support for
> each case which would lead to total of 24 DTB files. Along with these
> configurations, OEMs may also add certain additional board variants. Thus
> a mechanism is required to pick the correct DTB for the corresponding board.
>
> Introduce mechanism to select required DTB using newly introduced device
> tree properties "board-id" and "board-id-type". "board-id" will contain
> the list of values of "qcom,soc-id", "qcom,board-id", "qcom,pmic-id" or
> "qcom,oem-id". "board-id-types" contains the type of parameter which is
> entered. It can be either "qcom,soc-id", "qcom,board-id", "qcom,pmic-id"
> or "qcom,oem-id".
Thanks for working on this, it's nice to finally see this logic
documented in the kernel.
>
> Qualcomm based bootloader will use these properties to pick the best
> matched DTB to boot the device with.
>
> Signed-off-by: Amrit Anand <quic_amrianan@...cinc.com>
> ---
> Documentation/devicetree/bindings/arm/qcom.yaml | 90 +++++++++++++++++++++++++
> 1 file changed, 90 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/arm/qcom.yaml b/Documentation/devicetree/bindings/arm/qcom.yaml
> index 7f80f48..dc66ae9 100644
> --- a/Documentation/devicetree/bindings/arm/qcom.yaml
> +++ b/Documentation/devicetree/bindings/arm/qcom.yaml
> @@ -1100,6 +1100,76 @@ properties:
> kernel
> The property is deprecated.
>
> + board-id:
> + $ref: /schemas/types.yaml#/definitions/uint32-matrix
> + minItems: 2
> + description: |
> + Qualcomm specific bootloader uses multiple different identifiers
> + (qcom,soc-id, qcom,board-id, qcom,pmic-id, qcom,oem-id) to select
> + single Devicetree among list of Devicetrees. For different identifiers,
> + the selection can be done either based on exact match (where the
> + identifiers information coming from firmware should exactly match
> + the ones described in devicetree) or best match (firmware provided
> + identifier information closely matches with the one of the Devicetree).
> + Below table describes matching criteria for each identifier::
> + |----------------------------------------------------------------------|
> + | DT property | Individual fields | Exact | Best | Default |
> + |----------------------------------------------------------------------|
> + | qcom,soc-id | |
> + | | Chipset Id | Y | N | - |
> + | | SoC Revision | N | Y | - |
> + | qcom,board-id | |
> + | | Board Id | Y | N | - |
> + | | Board Major | N | Y | - |
> + | | Board Minor | N | Y | - |
> + | | Subtype | Y | N | 0 |
> + | | DDRtype | Y | N | 0 |
> + | | BootDevice Type | Y | N | 0 |
> + | qcom,pmic-id | |
> + | | Slave Id | Y | N | 0 |
> + | | PMIC Id | Y | N | 0 |
> + | | PMIC Major | N | Y | 0 |
> + | | PMIC Minor | N | Y | 0 |
> + | qcom,oem-id | |
> + | | OEM Id | Y | N | 0 |
> + |----------------------------------------------------------------------|
> + For best match, identifiers are matched based on following priority order::
> + SoC Revision > Board Major > Board Minor > PMIC Major > PMIC Minor
> +
> + board-id-types:
> + $ref: /schemas/types.yaml#/definitions/non-unique-string-array
> + description:
> + Each field and helper macros are defined at include/dt-bindings/arm/qcom,ids.
> + minItems: 2
> + items:
> + oneOf:
> + - const: qcom,soc-id
> + description:
> + Matches Qualcomm Technologies, Inc. boards with the specified SoC.
> + 2 integers are needed to describe a soc-id. The first integer is the
> + SoC ID and the second integer is the SoC revision.
> + qcom,soc-id = <soc-id soc-revision>
> + - const: qcom,board-id
> + description: |
> + Matches Qualcomm Technologies, Inc. boards with the specified board.
> + 2 integers are needed to describe a board-id. The first integer is the
> + board ID. The second integer is the board-subtype.
> + qcom,board-id = <board-id board-subtype>
> + - const: qcom,pmic-id
> + description: |
> + Qualcomm boards can be attached to multiple PMICs where slave-id (SID)
> + indicates the address of the bus on which the PMIC is attached. It can be
> + any number. The model for a PMIC indicates the PMIC name attached to bus
> + described by SID along with major and minor version. 2 integers are needed
> + to describe qcom,pmic-id. The first integer is the slave-id and the second integer
> + is the pmic model.
> + qcom,pmic-id = <pmic-sid pmic-model>
> + - const: qcom,oem-id
> + description: |
> + Matches Qualcomm Technologies, Inc. boards with the specified OEM ID.
> + 1 integer is needed to describe the oem-id.
> + qcom,oem-id = <oem-id>
> +
> allOf:
> # Explicit allow-list for older SoCs. The legacy properties are not allowed
> # on newer SoCs.
> @@ -1167,4 +1237,24 @@ allOf:
>
> additionalProperties: true
>
> +examples:
> + - |
> + #include <dt-bindings/arm/qcom,ids.h>
> + / {
> + model = "Qualcomm Technologies, Inc. sc7280 IDP SKU1 platform";
> + compatible = "qcom,sc7280-idp", "google,senor", "qcom,sc7280";
> +
> + #board-id-cells = <2>;
> + board-id = <QCOM_SOC_ID(SC7280) QCOM_SOC_REVISION(1)>,
> + <QCOM_SOC_ID(SC7280) QCOM_SOC_REVISION(2)>,
> + <QCOM_BOARD_ID(IDP, 1, 0) QCOM_BOARD_SUBTYPE(UFS, ANY, 1)>;
> + board-id-types = "qcom,soc-id",
> + "qcom,soc-id",
> + "qcom,board-id";
Forgive me if this is a particularly cynical view, but this seems
incredibly blatant, the "qcom,board-id" property is deprecated for
various good reasons, just using a key/value map where "qcom,board-id"
is a key doesn't change that. There are two main issues I have with the
proposal here:
1. This breaks backwards compatibility, millions of production devices
with bootloaders that will never receive another update might be
compatible with the downstream "qcom,board-id" property, but they won't
work with this.
2. A top level board-id property that isn't namespaced implies that it
isn't vendor specific, but the proposed implementation doesn't even
pretend to be vendor agnostic.
U-Boot also has some ideas around this issue, there you can pass in
multiple DTBs and provide some board specific "best match" function.
I think there's definitely some value in exposing this information, but
there's no good reason to define the same data as `qcom,board-id` while
breaking production bootloaders.
> +
> + #address-cells = <2>;
> + #size-cells = <2>;
> + };
> +
> +
> ...
--
// Caleb (they/them)
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