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

[Krzysztof Kozlowski]

On Mon, 9 Sep 2019 at 14:42, Maciej Falkowski <m.falkowski@xxxxxxxxxxx> wrote:
>
> Convert Samsung Exynos IOMMU H/W, System Memory Management Unit
> to newer dt-schema format.
>
> Signed-off-by: Maciej Falkowski <m.falkowski@xxxxxxxxxxx>
> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>

Hi Maciej,

Thanks for the patch. Few comments below.

> ---
>  .../bindings/iommu/samsung,sysmmu.txt         |  67 ------------
>  .../bindings/iommu/samsung,sysmmu.yaml        | 102 ++++++++++++++++++
>  2 files changed, 102 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..6c40dfb86899
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/samsung,sysmmu.yaml
> @@ -0,0 +1,102 @@
> +# 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

Add empty line between properties. Makes it easier to read.

> +  reg:
> +    description: A tuple of base address and size of System MMU registers.

Description not needed.

> +    maxItems: 1
> +  interrupts:
> +    description: |
> +      An interrupt specifier for interrupt signal of System MMU,
> +      according to the format defined by a particular interrupt
> +      controller.

Description not needed.

> +  clocks:
> +    description: Phandles for respective clocks described by clock-names.

Description not needed but I think number of elements is.

> +  clock-names:
> +    description: |
> +      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).
> +    minItems: 1
> +    maxItems: 2

Based on the description this can be up to three clocks.

Please declare the exact items within each combination (so either
sysmmu or aclk+pclk, plus optional master?). If this does not depend
on compatible, then oneOf could work. Then number of items could be
removed.

> +  "#iommu-cells":
> +    const: 0
> +    description: Should be <0>.

Description not needed.

> +  power-domains:

$ref: /schemas/types.yaml#/definitions/phandle

> +    description: |
> +      Required if the System MMU is needed to gate its power.
> +      Please refer to the following document:
> +      Documentation/devicetree/bindings/power/pd-samsung.txt
> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - clocks
> +  - clock-names
> +  - "#iommu-cells"
> +
> +examples:
> +  - |
> +    gsc_0: gsc@13e00000 {
> +      compatible = "samsung,exynos5-gsc";
> +      reg = <0x13e00000 0x1000>;
> +      interrupts = <0 85 0>;
> +      power-domains = <&pd_gsc>;
> +      clocks = <&clock 0>; //CLK_GSCL0

Missing space after //

> +      clock-names = "gscl";
> +      iommus = <&sysmmu_gsc0>;
> +    };
> +  - |

This is one example, not two.

Best regards,
Krzysztof

> +    sysmmu_gsc0: sysmmu@13e80000 {
> +      compatible = "samsung,exynos-sysmmu";
> +      reg = <0x13E80000 0x1000>;
> +      interrupt-parent = <&combiner>;
> +      interrupts = <2 0>;
> +      clock-names = "sysmmu", "master";
> +      clocks = <&clock 0>, // CLK_SMMU_GSCL0
> +               <&clock 0>; // CLK_GSCL0
> +      power-domains = <&pd_gsc>;
> +      #iommu-cells = <0>;
> +    };
> +
> --
> 2.17.1
>