Re: [PATCH v2] dt-bindings: arm: samsung: Convert Samsung Exynos IOMMU H/W, System MMU to dt-schema

[Krzysztof Kozlowski]

On Tue, 10 Sep 2019 at 17:52, Maciej Falkowski <m.falkowski@xxxxxxxxxxx> wrote:
>
> Convert Samsung Exynos IOMMU H/W, System Memory Management Unit
> to newer dt-schema format.
>
> Update clock description.
>
> Signed-off-by: Maciej Falkowski <m.falkowski@xxxxxxxxxxx>
> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> ---
> Hi Krzysztof,
>
> Thank you for feedback.
>
> New changes:
> - style fixes including missing empty lines,
> deletion of unneeded descriptions
>
> - fix mistake where one example was split
> into two separete ones.
>
> There are some updates with clock description. I have spoken with
> Marek Szyprowski and the right setup for clocks seems to be two pairs:
> "sysmmu" with optional "master" or a pair of "aclk" + "pclk".
>
> The option: "aclk" + "pclk" + "master" was never used in any
> of device bindings and there are none compilation problems with that.
>
> In so, clock-names are rewritten to handle this version
> and maximal clock number is set to two.
>
> Best regards,
> Maciej Falkowski
> ---
>  .../bindings/iommu/samsung,sysmmu.txt         |  67 -----------
>  .../bindings/iommu/samsung,sysmmu.yaml        | 112 ++++++++++++++++++
>  2 files changed, 112 insertions(+), 67 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/iommu/samsung,sysmmu.txt
>  create mode 100644 Documentation/devicetree/bindings/iommu/samsung,sysmmu.yaml
>
> diff --git a/Documentation/devicetree/bindings/iommu/samsung,sysmmu.txt b/Documentation/devicetree/bindings/iommu/samsung,sysmmu.txt
> deleted file mode 100644
> index 525ec82615a6..000000000000
> --- a/Documentation/devicetree/bindings/iommu/samsung,sysmmu.txt
> +++ /dev/null
> @@ -1,67 +0,0 @@
> -Samsung Exynos IOMMU H/W, System MMU (System Memory Management Unit)
> -
> -Samsung's Exynos architecture contains System MMUs that enables scattered
> -physical memory chunks visible as a contiguous region to DMA-capable peripheral
> -devices like MFC, FIMC, FIMD, GScaler, FIMC-IS and so forth.
> -
> -System MMU is an IOMMU and supports identical translation table format to
> -ARMv7 translation tables with minimum set of page properties including access
> -permissions, shareability and security protection. In addition, System MMU has
> -another capabilities like L2 TLB or block-fetch buffers to minimize translation
> -latency.
> -
> -System MMUs are in many to one relation with peripheral devices, i.e. single
> -peripheral device might have multiple System MMUs (usually one for each bus
> -master), but one System MMU can handle transactions from only one peripheral
> -device. The relation between a System MMU and the peripheral device needs to be
> -defined in device node of the peripheral device.
> -
> -MFC in all Exynos SoCs and FIMD, M2M Scalers and G2D in Exynos5420 has 2 System
> -MMUs.
> -* MFC has one System MMU on its left and right bus.
> -* FIMD in Exynos5420 has one System MMU for window 0 and 4, the other system MMU
> -  for window 1, 2 and 3.
> -* M2M Scalers and G2D in Exynos5420 has one System MMU on the read channel and
> -  the other System MMU on the write channel.
> -
> -For information on assigning System MMU controller to its peripheral devices,
> -see generic IOMMU bindings.
> -
> -Required properties:
> -- compatible: Should be "samsung,exynos-sysmmu"
> -- reg: A tuple of base address and size of System MMU registers.
> -- #iommu-cells: Should be <0>.
> -- interrupts: An interrupt specifier for interrupt signal of System MMU,
> -             according to the format defined by a particular interrupt
> -             controller.
> -- clock-names: Should be "sysmmu" or a pair of "aclk" and "pclk" to gate
> -              SYSMMU core clocks.
> -              Optional "master" if the clock to the System MMU is gated by
> -              another gate clock other core  (usually main gate clock
> -              of peripheral device this SYSMMU belongs to).
> -- clocks: Phandles for respective clocks described by clock-names.
> -- power-domains: Required if the System MMU is needed to gate its power.
> -         Please refer to the following document:
> -         Documentation/devicetree/bindings/power/pd-samsung.txt
> -
> -Examples:
> -       gsc_0: gsc@13e00000 {
> -               compatible = "samsung,exynos5-gsc";
> -               reg = <0x13e00000 0x1000>;
> -               interrupts = <0 85 0>;
> -               power-domains = <&pd_gsc>;
> -               clocks = <&clock CLK_GSCL0>;
> -               clock-names = "gscl";
> -               iommus = <&sysmmu_gsc0>;
> -       };
> -
> -       sysmmu_gsc0: sysmmu@13e80000 {
> -               compatible = "samsung,exynos-sysmmu";
> -               reg = <0x13E80000 0x1000>;
> -               interrupt-parent = <&combiner>;
> -               interrupts = <2 0>;
> -               clock-names = "sysmmu", "master";
> -               clocks = <&clock CLK_SMMU_GSCL0>, <&clock CLK_GSCL0>;
> -               power-domains = <&pd_gsc>;
> -               #iommu-cells = <0>;
> -       };
> diff --git a/Documentation/devicetree/bindings/iommu/samsung,sysmmu.yaml b/Documentation/devicetree/bindings/iommu/samsung,sysmmu.yaml
> new file mode 100644
> index 000000000000..85d1a251f2ff
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/samsung,sysmmu.yaml
> @@ -0,0 +1,112 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/samsung,sysmmu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Samsung Exynos IOMMU H/W, System MMU (System Memory Management Unit)
> +
> +maintainers:
> +  - Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> +
> +description: |+
> +  Samsung's Exynos architecture contains System MMUs that enables scattered
> +  physical memory chunks visible as a contiguous region to DMA-capable peripheral
> +  devices like MFC, FIMC, FIMD, GScaler, FIMC-IS and so forth.
> +
> +  System MMU is an IOMMU and supports identical translation table format to
> +  ARMv7 translation tables with minimum set of page properties including access
> +  permissions, shareability and security protection. In addition, System MMU has
> +  another capabilities like L2 TLB or block-fetch buffers to minimize translation
> +  latency.
> +
> +  System MMUs are in many to one relation with peripheral devices, i.e. single
> +  peripheral device might have multiple System MMUs (usually one for each bus
> +  master), but one System MMU can handle transactions from only one peripheral
> +  device. The relation between a System MMU and the peripheral device needs to be
> +  defined in device node of the peripheral device.
> +
> +  MFC in all Exynos SoCs and FIMD, M2M Scalers and G2D in Exynos5420 has 2 System
> +  MMUs.
> +  * MFC has one System MMU on its left and right bus.
> +  * FIMD in Exynos5420 has one System MMU for window 0 and 4, the other system MMU
> +    for window 1, 2 and 3.
> +  * M2M Scalers and G2D in Exynos5420 has one System MMU on the read channel and
> +    the other System MMU on the write channel.
> +
> +  For information on assigning System MMU controller to its peripheral devices,
> +  see generic IOMMU bindings.
> +
> +properties:
> +  compatible:
> +    const: samsung,exynos-sysmmu
> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    description: |
> +      An interrupt specifier for interrupt signal of System MMU,
> +      according to the format defined by a particular interrupt
> +      controller.

You left this description and it is not needed - does not bring any information.
Add also maxItems as I believe there should be only one interrupt.

> +
> +  clocks:
> +    minItems: 1
> +    maxItems: 2
> +
> +  clock-names:
> +    oneOf:
> +      - contains:
> +          enum:
> +            - sysmmu
> +            - master

This is not specific enough, because it accepts:
clock-names = "master";
clock-names = "aclk";

Instead I think this could work:
oneOf:
  - items:
    - const: sysmmu
  - items:
    - const: sysmmu
    - const: master
  - items:
    - const: aclk
    - const: pclk

Best regards,
Krzysztof