On Mon, Oct 26, 2015 at 02:25:10PM -0700, Stephen Boyd wrote:
> Some qcom based bootloaders identify the dtb blob based on a set
> of device properties like SoC, platform, PMIC, and revisions of
> those components. In downstream kernels, these values are added
> to the different component dtsi files (i.e. pmic dtsi file, SoC
> dtsi file, board dtsi file, etc.) via qcom specific DT
> properties. The dtb files are parsed by a program called dtbTool
> that picks out these properties and creates a table of contents
> binary blob with the property information and some offsets into
> the concatenation of all the dtbs (termed a QCDT image).
Got a pointer to what these properties look like?
> The suggestion is to do this via the board compatible string
> instead, because these qcom specific properties are never used by
> the kernel. Add a document describing the format of the
> compatible string that encodes all this information that's
> currently encoded in the qcom,{msm-id,board-id,pmic-id}
> properties in downstream devicetrees. Future bootloaders may be
> updated to look at the compatible field instead of looking for
> the table of contents image. For non-updateable bootloaders, a
> new dtbTool program will parse the compatible string and generate
> a QCDT image from it.
>
> Signed-off-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>
> ---
> Documentation/devicetree/bindings/arm/qcom.txt | 86 ++++++++++++++++++++++++++
> 1 file changed, 86 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/arm/qcom.txt
>
> diff --git a/Documentation/devicetree/bindings/arm/qcom.txt b/Documentation/devicetree/bindings/arm/qcom.txt
> new file mode 100644
> index 000000000000..ed084367182d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/arm/qcom.txt
> @@ -0,0 +1,86 @@
> +QCOM device tree bindings
> +-------------------------
> +
> +Some qcom based bootloaders identify the dtb blob based on a set of
> +device properties like SoC, platform, PMIC, and revisions of those components.
> +To support this scheme, we encode this information into the board compatible
> +string.
Why does all this need to be a single property?
> +Each board must specify a top-level board compatible string with the following
> +format:
> +
> + compatible = "qcom,<SoC>(-<soc_version>)(-<foundry_id>)-<plat_type>(/<subtype>)(-<plat_version>)(-<mb>MB)(-<panel>-panel)(-boot-<boot>)(-<pmic>(-v<pmic_version>)){0-4}"
> +
> +where elements in parentheses "()" are optional and elements in brackets "<>"
[] brackets are more generally used for optional params.
> +are names of elements. Meaning only the 'SoC' and 'plat_type' elements are
> +required.
> +
> +The 'SoC' element must be one of the following strings:
> +
> + apq8016
> + apq8074
> + apq8084
> + apq8096
> + msm8916
> + msm8974
> + msm8996
> +
> +The 'plat_type' element must be one of the following strings:
> +
> + cdp
> + liquid
> + dragonboard
> + mtp sbc
Platform is pretty overloaded meaning. Perhaps board_type would be more
clear.
> +
> +The 'soc_version', 'plat_version' and 'pmic_version' elements take the form of
> +v<Major>.<Minor> where the minor number may be omitted when it's zero, i.e.
> +v1.0 is the same as v1. If all versions of the 'plat_version' element's match,
> +then a wildcard '*' should be used, e.g. 'v*'.
> +
> +The 'foundry_id', 'subtype', and 'mb' elements are one or more digits from 0
> +to 9.
Can you define what these are exactly. I gather mb is RAM size.
> +
> +The 'panel' element must be one of the following strings:
> +
> + 720p
> + fWVGA
> + hd
> + qHD
How is this used?
> +The 'boot' element must be one of the following strings:
> +
> + emmc_sdc1
> + ufs
> +
> +The 'pmic' element must be one of the following strings:
> +
> + pm8841
> + pm8019
> + pm8110
> + pma8084
> + pmi8962
> + pmd9635
> + pm8994
> + pmi8994
> + pm8916
> + pm8004
> + pm8909
> +
> +The 'pmic' element is specified in order of ascending USID. The PMIC in USID0
> +goes first, and then USID2, USID4, and finally USID6. Up to four PMICs may be
> +specified and no holes in the USID number space are allowed.
What is USID?
> +
> +Examples:
> +
> + "qcom,msm8916-v1-cdp-pm8916-v2.1"
> +
> +A CDP board with an msm8916 SoC, version 1 paired with a pm8916 PMIC of version
> +2.1.
> +
> + "qcom,apq8074-v2.0-2-dragonboard/1-v0.1-512MB-panel-qHD-boot-emmc_sdc1-pm8941-v0.2-pm8909-v2.2-pma8084-v3-pm8110-v1"
Which example is more common?
> +
> +A dragonboard board v0.1 of subtype 1 with an apq8074 SoC version 2, made in
> +foundry 2 with 512MB of memory and a qHD panel booting from emmc_sdc1, paired
> +with a pm8941 PMIC version 0.2 at USID0, pm8909 PMIC version 2.2 at USID2,
> +pma8084 version 3 at USID4 and a pm8110 version 1 at USID6.
> --
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>
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