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    Subject[PATCH V2 1/5] arm64: dts: ti: k3-am65*: Cleanup disabled nodes at SoC dtsi level
    Date
    The device tree standard states that when the status property is
    not present under a node, the okay value is assumed. There are many
    reasons for doing the same, the number of strings in the device
    tree, default power management functionality, etc. are a few of the
    reasons.

    In general, after a few rounds of discussions [1] there are few
    options one could take when dealing with SoC dtsi and board dts

    a. SoC dtsi provide nodes as a super-set default (aka enabled) state and
    to prevent messy board files, when more boards are added per SoC, we
    optimize and disable commonly un-used nodes in board-common.dtsi
    b. SoC dtsi disables all hardware dependent nodes by default and board
    dts files enable nodes based on a need basis.
    c. Subjectively pick and choose which nodes we will disable by default
    in SoC dtsi and over the years we can optimize things and change
    default state depending on the need.

    While there are pros and cons on each of these approaches, the right
    thing to do will be to stick with device tree default standards and
    work within those established rules. So, we choose to go with option
    (a).

    Lets cleanup defaults of am654 SoC dtsi before this gets more harder
    to cleanup later on and new SoCs are added.

    The dtb generated is identical with the patch and it is just cleanup to
    ensure we have a clean usage model

    NOTE: There is a known risk of omission that new board dts developers
    might miss reviewing both the board schematics in addition to all the
    DT nodes of the SoC when setting appropriate nodes status to disable
    or reserved in the board dts. This can expose issues in drivers that
    may not anticipate an incomplete node (example: missing appropriate
    board properties) being in an "okay" state. These cases are considered
    bugs and need to be fixed in the drivers as and when identified.

    [1] https://lore.kernel.org/linux-arm-kernel/20201027130701.GE5639@atomide.com/

    Fixes: 9bcb631e9953 ("arm64: dts: ti: k3-am654-main: Add McASP nodes")
    Fixes: fc539b90eda2 ("arm64: dts: ti: am654: Add DSS node")
    Signed-off-by: Nishanth Menon <nm@ti.com>
    Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
    Cc: Jyri Sarha <jsarha@ti.com>
    Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
    Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
    Cc: Tony Lindgren <tony@atomide.com>
    ---

    Changes since v1:
    - commit message update

    V1: https://lore.kernel.org/linux-arm-kernel/20201104224356.18040-2-nm@ti.com/

    arch/arm64/boot/dts/ti/k3-am65-main.dtsi | 8 --------
    arch/arm64/boot/dts/ti/k3-am654-base-board.dts | 16 ++++++++++++++++
    2 files changed, 16 insertions(+), 8 deletions(-)

    diff --git a/arch/arm64/boot/dts/ti/k3-am65-main.dtsi b/arch/arm64/boot/dts/ti/k3-am65-main.dtsi
    index 533525229a8d..21e50021dd83 100644
    --- a/arch/arm64/boot/dts/ti/k3-am65-main.dtsi
    +++ b/arch/arm64/boot/dts/ti/k3-am65-main.dtsi
    @@ -770,8 +770,6 @@ mcasp0: mcasp@2b00000 {
    clocks = <&k3_clks 104 0>;
    clock-names = "fck";
    power-domains = <&k3_pds 104 TI_SCI_PD_EXCLUSIVE>;
    -
    - status = "disabled";
    };

    mcasp1: mcasp@2b10000 {
    @@ -789,8 +787,6 @@ mcasp1: mcasp@2b10000 {
    clocks = <&k3_clks 105 0>;
    clock-names = "fck";
    power-domains = <&k3_pds 105 TI_SCI_PD_EXCLUSIVE>;
    -
    - status = "disabled";
    };

    mcasp2: mcasp@2b20000 {
    @@ -808,8 +804,6 @@ mcasp2: mcasp@2b20000 {
    clocks = <&k3_clks 106 0>;
    clock-names = "fck";
    power-domains = <&k3_pds 106 TI_SCI_PD_EXCLUSIVE>;
    -
    - status = "disabled";
    };

    cal: cal@6f03000 {
    @@ -865,8 +859,6 @@ dss: dss@04a00000 {

    interrupts = <GIC_SPI 166 IRQ_TYPE_EDGE_RISING>;

    - status = "disabled";
    -
    dss_ports: ports {
    #address-cells = <1>;
    #size-cells = <0>;
    diff --git a/arch/arm64/boot/dts/ti/k3-am654-base-board.dts b/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
    index d12dd89f3405..199c4d4e7539 100644
    --- a/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
    +++ b/arch/arm64/boot/dts/ti/k3-am654-base-board.dts
    @@ -486,3 +486,19 @@ &cpsw_port1 {
    phy-mode = "rgmii-rxid";
    phy-handle = <&phy0>;
    };
    +
    +&mcasp0 {
    + status = "disabled";
    +};
    +
    +&mcasp1 {
    + status = "disabled";
    +};
    +
    +&mcasp2 {
    + status = "disabled";
    +};
    +
    +&dss {
    + status = "disabled";
    +};
    --
    2.29.2
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