soc: esp32xx: refactor clock and RTC subsystems

The RTC subsystem in espressif's SOCs, among other tasks
is responsible for clock selection for CPU and for low
power domain clocks such as RTC_SLOW and RTC_FAST.

This commit allows for proper clock source and rate
selection for CPU, using the espressif,riscv and
espressif,xtensa-lx6/7 bindings.

It also enables clock selection for RTC_FAST and RTC_SLOW,
that impacts some peripherals, such as rtc_timer.

Signed-off-by: Lucas Tamborrino <lucas.tamborrino@espressif.com>

dts/bindings/clock/espressif,esp32-rtc.yaml

@@ -11,14 +11,32 @@ properties:
   reg:
     required: true
 
-  xtal-freq:
+  fast-clk-src:
     type: int
     required: true
-    description: Value of the external XTAL connected to ESP32.
+    description: |
+      RTC fast clock source.
+      - 0: ESP32_RTC_FAST_CLK_SRC_XTAL_D2 - Main XTAL divided by 2 (C3/S3)
+      ESP32_RTC_FAST_CLK_SRC_XTAL_D4 Main XTAL divided by 4 (ESP32/S2)
+      - 1: ESP32_RTC_FAST_CLK_SRC_RC_FAST - 8 MHz
+    enum:
+      - 0
+      - 1
 
-  xtal-div:
+  slow-clk-src:
     type: int
-    description: Divisor value for XTAL Clock, CPU_CLK = XTAL_FREQ / xtal-div
+    required: true
+    description: |
+      RTC slow clock source. Default to
+      - 0: ESP32_RTC_SLOW_CLK_SRC_RC_SLOW - 136 KHz (C3/S3) - 90 kHz (S2) - 150 kHz (ESP32)
+      - 1: ESP32_RTC_SLOW_CLK_SRC_XTAL32K - 32,768U KHz
+      - 2: ESP32_RTC_SLOW_CLK_SRC_RC_FAST_D256 - 17,5 MHz
+      - 9: ESP32_RTC_SLOW_CLK_32K_EXT_OSC - External 32k oscillator connected to 32K_XP pin
+    enum:
+      - 0
+      - 1
+      - 2
+      - 9
 
   "#clock-cells":
     const: 1

dts/bindings/counter/espressif,esp32-rtc-timer.yaml

@@ -15,11 +15,4 @@ description: |
 
 include: base.yaml
 
-properties:
-  slow-clk-freq:
-    description: |
-      The slow clock input frequency for the RTC Timer.
-    type: int
-    required: true
-
 compatible: "espressif,esp32-rtc-timer"

dts/bindings/cpu/espressif,riscv.yaml

@@ -9,5 +9,24 @@ include: riscv,cpus.yaml
 
 properties:
   clock-source:
+    required: true
     type: int
-    description: cpu clock source
+    description: |
+      Defines the CPU clock source, each corresponding to different frequencies:
+      - 0: ESP32_CPU_CLK_SRC_XTAL - Uses the external crystal clock typically at 40 MHz.
+      - 1: ESP32_CPU_CLK_SRC_PLL - Utilizes an internal PLL which operates at either
+      320 MHz or 480 MHz.
+      - 2: ESP32_CPU_CLK_SRC_RC_FAST - Employs an internal fast RC oscillator with
+      frequency of 17.5 MHz.
+    enum:
+      - 0
+      - 1
+      - 2
+
+  xtal-freq:
+    required: true
+    type: int
+    description: Value of the external XTAL connected to ESP32. This is typically 40 MHz.
+    enum:
+      - 40000000
+      - 32000000

dts/bindings/cpu/espressif,xtensa-lx6.yaml

@@ -0,0 +1,34 @@
+# Copyright (c) 2024 Espressif Systems (Shanghai) Co., Ltd.
+# SPDX-License-Identifier: Apache-2.0
+
+description: Espressif Xtensa CPU
+
+compatible: "espressif,xtensa-lx6"
+
+include: cdns,tensilica-xtensa-lx6.yaml
+
+properties:
+  clock-source:
+    required: true
+    type: int
+    description: |
+      Defines the CPU clock source, each corresponding to different frequencies:
+      - 0: ESP32_CPU_CLK_SRC_XTAL - Uses the external crystal clock typically at 40 MHz.
+      - 1: ESP32_CPU_CLK_SRC_PLL - Utilizes an internal PLL which operates at either
+      320 MHz or 480 MHz.
+      - 2: ESP32_CPU_CLK_SRC_RC_FAST - Employs an internal fast RC oscillator with
+      frequency of 17.5 MHz. 8 MHz for ESP32S2.
+      - 3: APLL_CLK - 16 Mhz ~ 128 MHz
+    enum:
+      - 0
+      - 1
+      - 2
+      - 3
+
+  xtal-freq:
+    type: int
+    required: true
+    description: Value of the external XTAL connected to ESP32.
+    enum:
+      - 40000000
+      - 32000000

dts/bindings/cpu/espressif,xtensa-lx7.yaml

@@ -0,0 +1,34 @@
+# Copyright (c) 2024 Espressif Systems (Shanghai) Co., Ltd.
+# SPDX-License-Identifier: Apache-2.0
+
+description: Espressif Xtensa CPU
+
+compatible: "espressif,xtensa-lx7"
+
+include: cdns,tensilica-xtensa-lx7.yaml
+
+properties:
+  clock-source:
+    type: int
+    required: true
+    description: |
+      Defines the CPU clock source, each corresponding to different frequencies:
+      - 0: ESP32_CPU_CLK_SRC_XTAL - Uses the external crystal clock typically at 40 MHz.
+      - 1: ESP32_CPU_CLK_SRC_PLL - Utilizes an internal PLL which operates at either
+      320 MHz or 480 MHz.
+      - 2: ESP32_CPU_CLK_SRC_RC_FAST - Employs an internal fast RC oscillator with
+      frequency of 17.5 MHz. 8 MHz for ESP32S2.
+      - 3: APLL_CLK - 16 Mhz ~ 128 MHz (ESP32S2 Only)
+    enum:
+      - 0
+      - 1
+      - 2
+      - 3
+
+  xtal-freq:
+    type: int
+    required: true
+    description: Value of the external XTAL connected to ESP32.
+    enum:
+      - 40000000
+      - 32000000