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Date: Wed, 11 Sep 2019 08:26:48 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Maciej Falkowski <m.falkowski@...sung.com>
Cc: "linux-samsung-soc@...r.kernel.org"
<linux-samsung-soc@...r.kernel.org>, devicetree@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
robh+dt@...nel.org, mark.rutland@....com,
Marek Szyprowski <m.szyprowski@...sung.com>,
Andrzej Hajda <a.hajda@...sung.com>
Subject: Re: [PATCH v2] dt-bindings: arm: samsung: Convert Samsung Exynos
IOMMU H/W, System MMU to dt-schema
On Tue, 10 Sep 2019 at 17:52, Maciej Falkowski <m.falkowski@...sung.com> 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@...sung.com>
> Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
> ---
> 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@...00000 {
> - 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@...80000 {
> - 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@...sung.com>
> +
> +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
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