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Subject[PATCH v3 2/4] dt-bindings: clk: Add Baikal-T1 CCU Dividers binding
Date
After being gained by the CCU PLLs the signals must be transformed to
be suitable for the clock-consumers. This is done by a set of dividers
embedded into the CCU. A first block of dividers is used to create
reference clocks for AXI-bus of high-speed peripheral IP-cores of the
chip. The second block dividers alter the PLLs output signals to be then
consumed by SoC peripheral devices. Both block DT nodes are ordinary
clock-providers with standard set of properties supported. But in addition
to that each clock provider can be used to reset the corresponding clock
domain. This makes the AXI-bus and System Devices CCU DT nodes to be also
reset-providers.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-mips@vger.kernel.org

---

Changelog v2:
- Rearrange the SoBs.
- Combine AXI-bus and System Devices CCU bindings into a single file.
- Discard comments in the bindings file header.
- Add dual GPL/BSD license.
- Add spaces around the ASCII-graphics in the binding description.
- Remove reference to Documentation/devicetree/bindings/clock/clock-bindings.txt
file.
- Discard redundant object check against "/schemas/clock/clock.yaml#" schema.
- Discard redundant descriptions of "#clock-cells" and "#reset-cells"
properties.
- Discard "reg" property since the CCU dividers DT nodes are supposed be
children of the syscon-compatible system controller node.
- Remove "clock-output-names" property support.
- Replace "additionalProperties: false" with "unevaluatedProperties: false".
- Lowercase the nodes name in the examples.
- Use "clock-controller" node name suffix in the examples.
- Remove unnecessary comments in the clocks and resets dt-binding header
files.
- Discard label definitions in the examples.

Changelog v3:
- Get the reg property back even though the driver is using the parental
syscon regmap.
- The DT schema will live separately from the system controller, but the
corresponding sub-node of the later DT schema will $ref this one.
---
.../bindings/clock/baikal,bt1-ccu-div.yaml | 188 ++++++++++++++++++
include/dt-bindings/clock/bt1-ccu.h | 32 +++
include/dt-bindings/reset/bt1-ccu.h | 25 +++
3 files changed, 245 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/baikal,bt1-ccu-div.yaml
create mode 100644 include/dt-bindings/reset/bt1-ccu.h

diff --git a/Documentation/devicetree/bindings/clock/baikal,bt1-ccu-div.yaml b/Documentation/devicetree/bindings/clock/baikal,bt1-ccu-div.yaml
new file mode 100644
index 000000000000..2821425ee445
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/baikal,bt1-ccu-div.yaml
@@ -0,0 +1,188 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/clock/baikal,bt1-ccu-div.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Baikal-T1 Clock Control Unit Dividers
+
+maintainers:
+ - Serge Semin <fancer.lancer@gmail.com>
+
+description: |
+ Clocks Control Unit is the core of Baikal-T1 SoC System Controller
+ responsible for the chip subsystems clocking and resetting. The CCU is
+ connected with an external fixed rate oscillator, which signal is transformed
+ into clocks of various frequencies and then propagated to either individual
+ IP-blocks or to groups of blocks (clock domains). The transformation is done
+ by means of an embedded into CCU PLLs and gateable/non-gateable dividers. The
+ later ones are described in this binding. Each clock domain can be also
+ individually reset by using the domain clocks divider configuration
+ registers. Baikal-T1 CCU is logically divided into the next components:
+ 1) External oscillator (normally XTAL's 25 MHz crystal oscillator, but
+ in general can provide any frequency supported by the CCU PLLs).
+ 2) PLLs clocks generators (PLLs).
+ 3) AXI-bus clock dividers (AXI) - described in this binding file.
+ 4) System devices reference clock dividers (SYS) - described in this binding
+ file.
+ which are connected with each other as shown on the next figure:
+
+ +---------------+
+ | Baikal-T1 CCU |
+ | +----+------|- MIPS P5600 cores
+ | +-|PLLs|------|- DDR controller
+ | | +----+ |
+ +----+ | | | | |
+ |XTAL|--|-+ | | +---+-|
+ +----+ | | | +-|AXI|-|- AXI-bus
+ | | | +---+-|
+ | | | |
+ | | +----+---+-|- APB-bus
+ | +-------|SYS|-|- Low-speed Devices
+ | +---+-|- High-speed Devices
+ +---------------+
+
+ Each sub-block is represented as a separate DT node and has an individual
+ driver to be bound with.
+
+ In order to create signals of wide range frequencies the external oscillator
+ output is primarily connected to a set of CCU PLLs. Some of PLLs CLKOUT are
+ then passed over CCU dividers to create signals required for the target clock
+ domain (like AXI-bus or System Device consumers). The dividers have the
+ following structure:
+
+ +--------------+
+ CLKIN --|->+----+ 1|\ |
+ SETCLK--|--|/DIV|->| | |
+ CLKDIV--|--| | | |-|->CLKLOUT
+ LOCK----|--+----+ | | |
+ | |/ |
+ | | |
+ EN------|-----------+ |
+ RST-----|--------------|->RSTOUT
+ +--------------+
+
+ where CLKIN is the reference clock coming either from CCU PLLs or from an
+ external clock oscillator, SETCLK - a command to update the output clock in
+ accordance with a set divider, CLKDIV - clocks divider, LOCK - a signal of
+ the output clock stabilization, EN - enable/disable the divider block,
+ RST/RSTOUT - reset clocks domain signal. Depending on the consumer IP-core
+ peculiarities the dividers may lack of some functionality depicted on the
+ figure above (like EN, CLKDIV/LOCK/SETCLK). In this case the corresponding
+ clock provider just doesn't expose either switching functions, or the rate
+ configuration, or both of them.
+
+ The clock dividers, which output clock is then consumed by the SoC individual
+ devices, are united into a single clocks provider called System Devices CCU.
+ Similarly the dividers with output clocks utilized as AXI-bus reference clocks
+ are called AXI-bus CCU. Both of them use the common clock bindings with no
+ custom properties. The list of exported clocks and reset signals can be found
+ in the files: 'include/dt-bindings/clock/bt1-ccu.h' and
+ 'include/dt-bindings/reset/bt1-ccu.h'. Since System Devices and AXI-bus CCU
+ are a part of the Baikal-T1 SoC System Controller their DT nodes are supposed
+ to be a children of later one.
+
+if:
+ properties:
+ compatible:
+ contains:
+ const: baikal,bt1-ccu-axi
+
+then:
+ properties:
+ clocks:
+ items:
+ - description: CCU SATA PLL output clock
+ - description: CCU PCIe PLL output clock
+ - description: CCU Ethernet PLL output clock
+
+ clock-names:
+ items:
+ - const: sata_clk
+ - const: pcie_clk
+ - const: eth_clk
+
+else:
+ properties:
+ clocks:
+ items:
+ - description: External reference clock
+ - description: CCU SATA PLL output clock
+ - description: CCU PCIe PLL output clock
+ - description: CCU Ethernet PLL output clock
+
+ clock-names:
+ items:
+ - const: ref_clk
+ - const: sata_clk
+ - const: pcie_clk
+ - const: eth_clk
+
+properties:
+ compatible:
+ enum:
+ - baikal,bt1-ccu-axi
+ - baikal,bt1-ccu-sys
+
+ reg:
+ maxItems: 1
+
+ "#clock-cells":
+ const: 1
+
+ "#reset-cells":
+ const: 1
+
+unevaluatedProperties: false
+
+required:
+ - compatible
+ - "#clock-cells"
+ - clocks
+ - clock-names
+
+examples:
+ # AXI-bus Clock Control Unit node:
+ - |
+ #include <dt-bindings/clock/bt1-ccu.h>
+
+ clock-controller@1f04d030 {
+ compatible = "baikal,bt1-ccu-axi";
+ reg = <0x1f04d030 0x030>;
+ #clock-cells = <1>;
+ #reset-cells = <1>;
+
+ clocks = <&ccu_pll CCU_SATA_PLL>,
+ <&ccu_pll CCU_PCIE_PLL>,
+ <&ccu_pll CCU_ETH_PLL>;
+ clock-names = "sata_clk", "pcie_clk", "eth_clk";
+ };
+ # System Devices Clock Control Unit node:
+ - |
+ #include <dt-bindings/clock/bt1-ccu.h>
+
+ clock-controller@1f04d060 {
+ compatible = "baikal,bt1-ccu-sys";
+ reg = <0x1f04d060 0x0a0>;
+ #clock-cells = <1>;
+ #reset-cells = <1>;
+
+ clocks = <&clk25m>,
+ <&ccu_pll CCU_SATA_PLL>,
+ <&ccu_pll CCU_PCIE_PLL>,
+ <&ccu_pll CCU_ETH_PLL>;
+ clock-names = "ref_clk", "sata_clk", "pcie_clk",
+ "eth_clk";
+ };
+ # Required Clock Control Unit PLL node:
+ - |
+ ccu_pll: clock-controller@1f04d000 {
+ compatible = "baikal,bt1-ccu-pll";
+ reg = <0x1f04d000 0x028>;
+ #clock-cells = <1>;
+
+ clocks = <&clk25m>;
+ clock-names = "ref_clk";
+ };
+...
diff --git a/include/dt-bindings/clock/bt1-ccu.h b/include/dt-bindings/clock/bt1-ccu.h
index 931a4bea67c0..5f166d27a00a 100644
--- a/include/dt-bindings/clock/bt1-ccu.h
+++ b/include/dt-bindings/clock/bt1-ccu.h
@@ -13,4 +13,36 @@
#define CCU_PCIE_PLL 3
#define CCU_ETH_PLL 4

+#define CCU_AXI_MAIN_CLK 0
+#define CCU_AXI_DDR_CLK 1
+#define CCU_AXI_SATA_CLK 2
+#define CCU_AXI_GMAC0_CLK 3
+#define CCU_AXI_GMAC1_CLK 4
+#define CCU_AXI_XGMAC_CLK 5
+#define CCU_AXI_PCIE_M_CLK 6
+#define CCU_AXI_PCIE_S_CLK 7
+#define CCU_AXI_USB_CLK 8
+#define CCU_AXI_HWA_CLK 9
+#define CCU_AXI_SRAM_CLK 10
+
+#define CCU_SYS_SATA_REF_CLK 0
+#define CCU_SYS_APB_CLK 1
+#define CCU_SYS_GMAC0_TX_CLK 2
+#define CCU_SYS_GMAC0_PTP_CLK 3
+#define CCU_SYS_GMAC1_TX_CLK 4
+#define CCU_SYS_GMAC1_PTP_CLK 5
+#define CCU_SYS_XGMAC_REF_CLK 6
+#define CCU_SYS_XGMAC_PTP_CLK 7
+#define CCU_SYS_USB_CLK 8
+#define CCU_SYS_PVT_CLK 9
+#define CCU_SYS_HWA_CLK 10
+#define CCU_SYS_UART_CLK 11
+#define CCU_SYS_I2C1_CLK 12
+#define CCU_SYS_I2C2_CLK 13
+#define CCU_SYS_GPIO_CLK 14
+#define CCU_SYS_TIMER0_CLK 15
+#define CCU_SYS_TIMER1_CLK 16
+#define CCU_SYS_TIMER2_CLK 17
+#define CCU_SYS_WDT_CLK 18
+
#endif /* __DT_BINDINGS_CLOCK_BT1_CCU_H */
diff --git a/include/dt-bindings/reset/bt1-ccu.h b/include/dt-bindings/reset/bt1-ccu.h
new file mode 100644
index 000000000000..3578e83026bc
--- /dev/null
+++ b/include/dt-bindings/reset/bt1-ccu.h
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2020 BAIKAL ELECTRONICS, JSC
+ *
+ * Baikal-T1 CCU reset indices
+ */
+#ifndef __DT_BINDINGS_RESET_BT1_CCU_H
+#define __DT_BINDINGS_RESET_BT1_CCU_H
+
+#define CCU_AXI_MAIN_RST 0
+#define CCU_AXI_DDR_RST 1
+#define CCU_AXI_SATA_RST 2
+#define CCU_AXI_GMAC0_RST 3
+#define CCU_AXI_GMAC1_RST 4
+#define CCU_AXI_XGMAC_RST 5
+#define CCU_AXI_PCIE_M_RST 6
+#define CCU_AXI_PCIE_S_RST 7
+#define CCU_AXI_USB_RST 8
+#define CCU_AXI_HWA_RST 9
+#define CCU_AXI_SRAM_RST 10
+
+#define CCU_SYS_SATA_REF_RST 0
+#define CCU_SYS_APB_RST 1
+
+#endif /* __DT_BINDINGS_RESET_BT1_CCU_H */
--
2.26.2
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