- NXP LPC1850 Clock Generation Unit (CGU)
The CGU generates multiple independent clocks for the core and the
peripheral blocks of the LPC18xx. Each independent clock is called
a base clock and itself is one of the inputs to the two Clock
Control Units (CCUs) which control the branch clocks to the
individual peripherals.
The CGU selects the inputs to the clock generators from multiple
clock sources, controls the clock generation, and routes the outputs
of the clock generators through the clock source bus to the output
stages. Each output stage provides an independent clock source and
corresponds to one of the base clocks for the LPC18xx.
- Above text taken from NXP LPC1850 User Manual.
This binding uses the common clock binding:
Documentation/devicetree/bindings/clock/clock-bindings.txt
Required properties:
- compatible:
Should be “nxp,lpc1850-cgu” - reg:
Shall define the base and range of the address space
containing clock control registers - #clock-cells:
Shall have value <1>. The permitted clock-specifier values
are the base clock numbers defined below. - clocks:
Shall contain a list of phandles for the external input
sources to the CGU. The list shall be in the following
order: xtal, 32khz, enet_rx_clk, enet_tx_clk, gp_clkin. - clock-indices:
Shall be an ordered list of numbers defining the base clock
number provided by the CGU. - clock-output-names:
Shall be an ordered list of strings defining the names of
the clocks provided by the CGU.
Which base clocks that are available on the CGU depends on the
specific LPC part. Base clocks are numbered from 0 to 27.
Number: Name: Description:
0 BASE_SAFE_CLK Base safe clock (always on) for WWDT
1 BASE_USB0_CLK Base clock for USB0
2 BASE_PERIPH_CLK Base clock for Cortex-M0SUB subsystem,
SPI, and SGPIO
3 BASE_USB1_CLK Base clock for USB1
4 BASE_CPU_CLK System base clock for ARM Cortex-M core
and APB peripheral blocks #0 and #2
5 BASE_SPIFI_CLK Base clock for SPIFI
6 BASE_SPI_CLK Base clock for SPI
7 BASE_PHY_RX_CLK Base clock for Ethernet PHY Receive clock
8 BASE_PHY_TX_CLK Base clock for Ethernet PHY Transmit clock
9 BASE_APB1_CLK Base clock for APB peripheral block # 1
10 BASE_APB3_CLK Base clock for APB peripheral block # 3
11 BASE_LCD_CLK Base clock for LCD
12 BASE_ADCHS_CLK Base clock for ADCHS
13 BASE_SDIO_CLK Base clock for SD/MMC
14 BASE_SSP0_CLK Base clock for SSP0
15 BASE_SSP1_CLK Base clock for SSP1
16 BASE_UART0_CLK Base clock for UART0
17 BASE_UART1_CLK Base clock for UART1
18 BASE_UART2_CLK Base clock for UART2
19 BASE_UART3_CLK Base clock for UART3
20 BASE_OUT_CLK Base clock for CLKOUT pin
24-21 - Reserved
25 BASE_AUDIO_CLK Base clock for audio system (I2S)
26 BASE_CGU_OUT0_CLK Base clock for CGU_OUT0 clock output
27 BASE_CGU_OUT1_CLK Base clock for CGU_OUT1 clock output
BASE_PERIPH_CLK and BASE_SPI_CLK is only available on LPC43xx.
BASE_ADCHS_CLK is only available on LPC4370.
Example board file:
/ {
clocks {
xtal: xtal {
compatible = “fixed-clock”;
#clock-cells = <0>;
clock-frequency = <12000000>;
};
xtal32: xtal32 {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <32768>;
};
enet_rx_clk: enet_rx_clk {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <0>;
clock-output-names = "enet_rx_clk";
};
enet_tx_clk: enet_tx_clk {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <0>;
clock-output-names = "enet_tx_clk";
};
gp_clkin: gp_clkin {
compatible = "fixed-clock";
#clock-cells = <0>;
clock-frequency = <0>;
clock-output-names = "gp_clkin";
};
};
soc {
cgu: clock-controller@40050000 {
compatible = "nxp,lpc1850-cgu";
reg = <0x40050000 0x1000>;
#clock-cells = <1>;
clocks = <&xtal>, <&creg_clk 1>, <&enet_rx_clk>, <&enet_tx_clk>, <&gp_clkin>;
};
/* A CGU and CCU clock consumer */
lcdc: lcdc@40008000 {
...
clocks = <&cgu BASE_LCD_CLK>, <&ccu1 CLK_CPU_LCD>;
clock-names = "clcdclk", "apb_pclk";
...
};
};
};
