[bootlin/training-materials updates] master: kernel: porting: Adapt the Crystalfontz DT description (2ec4aff7)
Miquel Raynal
miquel.raynal at bootlin.com
Fri Jun 25 14:39:49 CEST 2021
Repository : https://github.com/bootlin/training-materials
On branch : master
Link : https://github.com/bootlin/training-materials/commit/2ec4aff7e618aaab24837859a18addc8cab63b3f
>---------------------------------------------------------------
commit 2ec4aff7e618aaab24837859a18addc8cab63b3f
Author: Miquel Raynal <miquel.raynal at bootlin.com>
Date: Fri Jun 25 14:31:59 2021 +0200
kernel: porting: Adapt the Crystalfontz DT description
These changes rework the way the Crystalfontz board is being described before
maybe another board (64-bit) gets introduced:
- Instead of showing the raw content of its device tree written with a
rather legacy syntax, I took the freedom to describe the nodes as I
think they *should* be described with today's habits.
- The ordering is also updated and the way the nodes are presented
contains the parent node when relevant in order to show how a device
tree gets constructed more than how a device tree can be read.
- I also dropped the MMC description which did not bring anything useful
to my eyes.
Signed-off-by: Miquel Raynal <miquel.raynal at bootlin.com>
>---------------------------------------------------------------
2ec4aff7e618aaab24837859a18addc8cab63b3f
.../kernel-porting-content.tex | 235 ++++++++++-----------
1 file changed, 109 insertions(+), 126 deletions(-)
diff --git a/slides/kernel-porting-content/kernel-porting-content.tex b/slides/kernel-porting-content/kernel-porting-content.tex
index fbf41019..6680bff4 100644
--- a/slides/kernel-porting-content/kernel-porting-content.tex
+++ b/slides/kernel-porting-content/kernel-porting-content.tex
@@ -137,182 +137,164 @@
\begin{frame}[fragile]
\frametitle{Crystalfontz CFA-10036 Device Tree, header}
\begin{itemize}
+ \item SPDX license tag\\
\item Mandatory Device Tree language definition\\
- \begin{block}{} \mint[fontsize=\small]{perl}+/dts-v1/+ \end{block}
+ \begin{block}{} \mint[fontsize=\small]{perl}+/dts-v1/;+ \end{block}
\item Include the \code{.dtsi} file describing the SoC\\
\begin{block}{}
\mint[fontsize=\small]{perl}+#include "imx28.dtsi"+
\end{block}
- \item Start the root of the tree\\
- \begin{block}{} \mint[fontsize=\small]{perl}+/ {+ \end{block}
- \item A human-readable string to describe the machine (shown at boot time)\\
- \begin{block}{}
- \mint[fontsize=\small]{perl}+model = "Crystalfontz CFA-10036 Board";+
- \end{block}
- \item A list of {\em compatible} strings, from the most specific one
- to the most general one. Mandatory to execute the right SoC specific
- initializations and board specific code.\\
- \begin{block}{}
- \mint[fontsize=\small]{perl}+compatible = "crystalfontz,cfa10036", "fsl,imx28";+
- \end{block}
+ \item Start the root of the tree (named \code{/}) then describe the board
+ \begin{itemize}
+ \item A human-readable string to describe the machine (shown at boot time)\\
+ \begin{block}{}
+ \mint[fontsize=\small]{perl}+model = "Crystalfontz CFA-10036 Board";+
+ \end{block}
+ \item A list of {\em compatible} strings, from the most specific one
+ to the most general one. Mandatory to execute the right SoC specific
+ initializations and board specific code.\\
+ \begin{block}{}
+ \mint[fontsize=\small]{perl}+compatible = "crystalfontz,cfa10036", "fsl,imx28";+
+ \end{block}
+ \end{itemize}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036 Device Tree, chosen/memory}
+ \frametitle{Crystalfontz CFA-10036, backbone}
\begin{itemize}
- \item Definition of the default {\em kernel command line}. Some
- additional operating-system specific entries can be added in
- \code{chosen}:
+ \item Definition of the buses and peripherals
\begin{block}{}
- \begin{minted}[fontsize=\footnotesize]{perl}
-chosen {
- bootargs = "console=ttyS0,115200 earlyprintk";
-};
-\end{minted}
-\end{block}
-\item Definition of the size and location of the RAM:
- \begin{block}{}
- \begin{minted}[fontsize=\footnotesize]{perl}
-memory {
+ \begin{minted}[fontsize=\small]{perl}
+/ {
+ /* Define here 'standalone' peripherals and internal buses */
+ memory {
device_type = "memory";
reg = <0x40000000 0x8000000>; /* 128 MB */
+ };
+ apb at 80000000 {
+ apbh at 80000000 {
+ /* Define apbh peripherals here */
+ apbx at 80040000 {
+ /* Define apbx peripherals here */
+ };
+ };
+ };
};
+/* Reference here existing nodes with their labels */
\end{minted}
\end{block}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036, bus/UART}
+ \frametitle{Crystalfontz CFA-10036 Device Tree, enable already
+ described devices}
\begin{itemize}
- \item Start of the internal SoC peripherals.
+ \item The CFA-10036 has one debug UART. It is described in the iMX28
+ DTSI file, so the corresponding controller should be referenced in
+ the board DTS and enabled:
\begin{block}{}
- \begin{minted}[fontsize=\small]{perl}
-apb at 80000000 {
- apbh at 80000000 {
- apbx at 80040000 {
-\end{minted}
-\end{block}
-\item The CFA-10036 has one debug UART, so the corresponding
- controller is enabled:
- \begin{block}{}
- \begin{minted}[fontsize=\small]{perl}
-duart: serial at 80074000 {
+ \begin{minted}[fontsize=\small]{perl}
+&duart {
pinctrl-names = "default";
pinctrl-0 = <&duart_pins_b>;
status = "okay";
};
- \end{minted}
- \end{block}
-\end{itemize}
-\end{frame}
-
-\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036 Device Tree, Muxing}
-\begin{itemize}
- \item Definition of a few pins that will be muxed as GPIO, for LEDs and reset.
- \begin{block}{}
- \begin{minted}[fontsize=\tiny]{perl}
-pinctrl at 80018000 {
- ssd1306_cfa10036: ssd1306-10036 at 0 {
- reg = <0>;
- fsl,pinmux-ids = <
- 0x2073 /* MX28_PAD_SSP0_D7__GPIO_2_7 */
- >;
- fsl,drive-strength = <0>;
- fsl,voltage = <1>;
- fsl,pull-up = <0>;
- };
-
- led_pins_cfa10036: leds-10036 at 0 {
- reg = <0>;
- fsl,pinmux-ids = <
- 0x3043 /* MX28_PAD_AUART1_RX__GPIO_3_4 */
- >;
- fsl,drive-strength = <0>;
- fsl,voltage = <1>;
- fsl,pull-up = <0>;
- };
+ \end{minted}
+ \end{block}
+ \item It also features an USB port which is described in the SoC
+ DTSI but needs to be enabled:
+ \begin{block}{}
+ \begin{minted}[fontsize=\small]{perl}
+&usb0 {
+ pinctrl-names = "default";
+ pinctrl-0 = <&usb0_otg_cfa10036>;
+ status = "okay";
};
- \end{minted}
- \end{block}
+ \end{minted}
+ \end{block}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036 Device Tree, LED}
-\begin{itemize}
-\item One LED is connected to this platform. Note the reference to the
- \code{led_pins_cfa10036} muxing configuration.
- \begin{block}{}
- \begin{minted}[fontsize=\small]{perl}
-leds {
- compatible = "gpio-leds";
- pinctrl-names = "default";
- pinctrl-0 = <&led_pins_cfa10036>;
+ \frametitle{Crystalfontz CFA-10036 Device Tree, fully describe
+ additional devices}
+ \begin{itemize}
+ \item The I2C bus with a Solomon SSD1306 OLED display connected on
+ it must be described entirely at the location where it belongs:
+ \begin{block}{}
+ \begin{minted}[fontsize=\tiny]{perl}
+apbc at 80040000 {
+ i2c0: i2c at 18000 { /* This means physical offset 0x80058000 */
+ reg = <0x18000 0x1000>;
+ pinctrl-names = "default";
+ pinctrl-0 = <&i2c0_pins_b>;
+ status = "okay";
+ clock-frequency = <400000>;
- power {
- gpios = <&gpio3 4 1>;
- default-state = "on";
+ ssd1306: oled at 3c {
+ compatible = "solomon,ssd1306fb-i2c";
+ pinctrl-names = "default";
+ pinctrl-0 = <&ssd1306_cfa10036>;
+ reg = <0x3c>;
+ reset-gpios = <&gpio2 7 0>;
+ solomon,height = <32>;
+ solomon,width = <128>;
+ solomon,page-offset = <0>;
+ };
};
-};
- \end{minted}
+ \end{minted}
\end{block}
+ \item Mind the display's pin configuration that has not yet been
+ described
\end{itemize}
\end{frame}
\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036 Device Tree, SD Card/USB}
+ \frametitle{Crystalfontz CFA-10036 Device Tree, LEDs}
\begin{itemize}
- \item The platform also has a USB port
+ \item One LED is connected to this platform, let's describe it as well
\begin{block}{}
\begin{minted}[fontsize=\small]{perl}
-usb0: usb at 80080000 {
- pinctrl-names = "default";
- pinctrl-0 = <&usb0_otg_cfa10036>;
- status = "okay";
-};
+/ {
+ leds {
+ compatible = "gpio-leds";
+ pinctrl-names = "default";
+ pinctrl-0 = <&led_pins_cfa10036>;
+
+ power {
+ gpios = <&gpio3 4 1>;
+ default-state = "on";
+ };
+ };
\end{minted}
\end{block}
- \item and an SD Card slot:
- \begin{block}{}
- \begin{minted}[fontsize=\small]{perl}
-ssp0: ssp at 80010000 {
- compatible = "fsl,imx28-mmc";
- pinctrl-names = "default";
- pinctrl-0 = <&mmc0_4bit_pins_a
- &mmc0_cd_cfg &mmc0_sck_cfg>;
- bus-width = <4>;
- status = "okay";
-};
- \end{minted}
- \end{block}
+ \item Also mind the pin configuration that we can define at any place
\end{itemize}
\end{frame}
\begin{frame}[fragile]
- \frametitle{Crystalfontz CFA-10036 Device Tree, I2C bus}
+ \frametitle{Crystalfontz CFA-10036 Device Tree, muxing}
\begin{itemize}
- \item An I2C bus, with a Solomon SSD1306 OLED display connected on
- it:
+ \item Definition of a few pins that will be muxed as GPIO, for LEDs and reset.
\begin{block}{}
\begin{minted}[fontsize=\tiny]{perl}
-i2c0: i2c at 80058000 {
- pinctrl-names = "default";
- pinctrl-0 = <&i2c0_pins_b>;
- clock-frequency = <400000>;
- status = "okay";
+&pinctrl {
+ ssd1306_cfa10036: ssd1306-10036 at 0 {
+ reg = <0>;
+ fsl,pinmux-ids = <0x2073>; /* MX28_PAD_SSP0_D7__GPIO_2_7 */
+ fsl,drive-strength = <0>;
+ fsl,voltage = <1>;
+ fsl,pull-up = <0>;
+ };
- ssd1306: oled at 3c {
- compatible = "solomon,ssd1306fb-i2c";
- pinctrl-names = "default";
- pinctrl-0 = <&ssd1306_cfa10036>;
- reg = <0x3c>;
- reset-gpios = <&gpio2 7 0>;
- solomon,height = <32>;
- solomon,width = <128>;
- solomon,page-offset = <0>;
+ led_pins_cfa10036: leds-10036 at 0 {
+ reg = <0>;
+ fsl,pinmux-ids = <0x3043>; /* MX28_PAD_AUART1_RX__GPIO_3_4 */
+ fsl,drive-strength = <0>;
+ fsl,voltage = <1>;
+ fsl,pull-up = <0>;
};
};
\end{minted}
@@ -343,7 +325,8 @@ i2c0: i2c at 80058000 {
\kfile{arch/arm/boot/dts/Makefile}:
\begin{block}{}
\begin{minted}{make}
-dtb-$(CONFIG_ARCH_MXS) += imx28-cfa10036.dtb \
+dtb-$(CONFIG_ARCH_MXS) +=
+ imx28-cfa10036.dtb \
imx28-cfa10037.dtb \
imx28-cfa10049.dtb \
imx28-cfa10055.dtb \
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