I need to add some board-specific code to a Linux kernel which I am building.
(I know I should be using device-tree already, but the driver I'm inspired by doesn't and I'm already learning a dozen new things before breakfast. Adding device-tree will also add another set of changes to debug. Once I have my platform-driver/drivers working using a board file, I will convert them to device tree.)
I have a file called arch/arm/myboard/myboard.c.
Where do I find existing board files in make menuconfig? (Such as http://lxr.free-electrons.com/source/arch/arm/mach-imx/mach-mx31ads.c?v=4.4 ?)
How do I make my board appear here also.
Take a look at the Makefile in the same directory. For mach-mx31ads.c, it has,
# i.MX31 based machines
obj-$(CONFIG_MACH_MX31ADS) += mach-mx31ads.o
The Kconfig has a corresponding entry,
config MACH_MX31ADS
bool "Support MX31ADS platforms"
default y
select IMX_HAVE_PLATFORM_IMX_I2C
select IMX_HAVE_PLATFORM_IMX_SSI
select IMX_HAVE_PLATFORM_IMX_UART
select SOC_IMX31
help
Include support for MX31ADS platform. This includes specific
configurations for the board and its peripherals.
Adding these will give your board a Kconfig menu item and build the file. The only other missing piece is a machine type. You need to add this to arm/tools/mach-type which is processed by the kernel makefile, using the gen-mach-types script, to create a generated/mach-type.h. You use this in your board file to create a static machine description (put in a special section).
MACHINE_START(MX31ADS, "Freescale MX31ADS")
/* Maintainer: Freescale Semiconductor, Inc. */
.atag_offset = 0x100,
.map_io = mx31ads_map_io,
.init_early = imx31_init_early,
.init_irq = mx31ads_init_irq,
.init_time = mx31ads_timer_init,
.init_machine = mx31ads_init,
.restart = mxc_restart,
MACHINE_END
The machine_desc structure is found in arch.h. You don't need to add all the elements as they won't be called if not present. The kernel init looks a the machine ATAG and iterates through the sections to match the machine that the boot loader passes in. Locating the machine_desc is done in assembler very early in the linux boot.
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Say I would like to make changes to the following Device Tree node in this Device Tree for U-boot:
/* SDHCI is used to control the SDIO for wireless */
&sdhci {
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&emmc_gpio34>;
status = "okay";
bus-width = <4>;
non-removable;
mmc-pwrseq = <&wifi_pwrseq>;
brcmf: wifi#1 {
reg = <1>;
compatible = "brcm,bcm4329-fmac";
};
};
In my case, I would like to change the following line:
pinctrl-0 = <&emmc_gpio34>;
to
pinctrl-0 = <&sdhost_gpio48>;
Can I create a Device Tree overlay and apply this overlay via U-boot commands once U-boot is running?
My goal is that I want U-boot's device tree to be adjusted in the above manner when I run my standalone binary via U-boot's go command.
The overlay that I have created is here:
/dts-v1/;
/plugin/;
/ {
compatible = "raspberrypi,3-model-b-plus", "brcm,bcm2837";
model = "Raspberry Pi 3 Model B+";
fragment#0 {
target = <&sdhci>;
__overlay__ {
#address-cells = <1>;
#size-cells = <0>;
pinctrl-names = "default";
pinctrl-0 = <&sdhost_gpio48>;
status = "okay";
bus-width = <4>;
non-removable;
mmc-pwrseq = <&wifi_pwrseq>;
brcmf: wifi#1 {
reg = <1>;
compatible = "brcm,bcm4329-fmac";
};
};
};
};
I've been broadly following U-boot's documentation here regarding loading and applying Device Tree overlays; however, I've noticed this documentation doesn't seem applicable to what I'm trying to achieve. Below are the steps I have taken so far:
I first create the fdtovaddr environment variable like so:
U-Boot> setenv fdtovaddr 0x1000000
Then I load my compiled overlay into fdtovaddr:
U-Boot> fatload mmc 0 ${fdtovaddr} sdhci_overlay.dtbo
Then I specify the base binary device tree as U-boot's Device Tree like so:
U-Boot> fdt addr ${fdt_addr}
Then I try to apply my overlay like so:
U-Boot> fdt apply ${fdtovaddr}
However, I get the following output:
failed on fdt_overlay_apply(): FDT_ERR_BADMAGIC
base fdt does did not have a /__symbols__ node
make sure you've compiled with -#
This makes sense because as per the docs, the base U-Boot Device Tree needs to be compiled with the -# command line switch and I'm assuming U-Boot's Device Tree was not:
It requires both the base device-tree and all the overlays to be compiled with the -# command line switch of the device-tree compiler so that symbol information is included.
The second part of the docs that made me realise the docs were not addressing my needs were the commands listed for booting the system as shown below:
Boot system like you would do with a traditional dtb.
For bootm:
=> bootm ${kerneladdr} - ${fdtaddr}
For bootz:
=> bootz ${kerneladdr} - ${fdtaddr}
The above commands are for passing the resultant overlayed Device Tree to a Linux Kernel Image via either the bootm or bootz shell command. This makes sense considering Linux uses a Device Tree to determine hardware availability etc and we are passing it a modified one via the above boot commands.
However, I would like to run a standalone via U-boot's go <address> command instead, which I believe doesn't accept an argument for a Device Tree (doesn't really make sense to either).
As such, is the conclusion that I've personally reached correct that it is not possible to manipulate U-boot's device tree while U-boot is running? Is the only option to manipulate U-boot's device tree manually and compile U-boot to generate a U-boot binary with my desired U-Boot Device Tree changes?
If not, please let me know how I can overlay U-boot's device tree during U-boot's runtime.
In a single chip system, TRACE32 could use SYStem.DETECT DAP to access the single root ROM table in DAP to idendify and discover the system. Then how in a multichip system?
For example, in a system of 2 chips, each of which has its own DAP and ROM table, and the two DAPs are connected in daisy chain. What will SYStem.DETECT DAP do? And how is the system identified?
Select the DAP within the JTAG daisy chain by setting up the correct pre- and post-bits with the four commands
SYStem.CONFIG.DAIRPRE, SYStem.CONFIG.DAIRPOST, SYStem.CONFIG.DADRPRE and SYStem.CONFIG.DADRPOST.
To find the right values for the pre- and post-bits you can use the command SYStem.DETECT.SHOWChain. It opens a window which allows you to set the pre/post-bits directly from there via a context menu:
Afterwards SYStem.DETECT.DAP examines the DAP which is accessible with the previously defined pre/post-bits.
We have a ARM + DSP set up. Each has a specific invocation, the former uses the tmarm.exe and the latter uses the t32m6000.exe with the config.t32 file. What I want to know is, I have a cmm script that starts the ARM instance and then does a bunch of things and then it starts the DSP instance but after starting I don't know how to send commands to it. I am using the T32 lib via MATLAB so at one point I do a system('C6000start.bat') in MATLAB which issues the call to start the DSP and the DSP instance starts up but in the next line if I send any command to it it won't work. In the config6000.t32 file I have commented out the RCL, PORT and PACKLEN directives since t32m6000.exe flags a syntax error and I concluded that those directives only apply to the ARM.
I don't know if I have to use the INTERCOM command to switch focus to the DSP instance.
========== batch file C6000start.bat ===============
start "" %t32path%\t32m6000 -c config6000.t32
=====================================================
=============== config6000.t32=====================
; Environment variables
OS=
ID=T32
SYS=C:\T32
; USB information
PBI=
USB
; Printer settings
PRINTER=WINDOWS
; Remote Control Access
; Printer settings
PRINTER=WINDOWS
; Remote Control Access
;RCL=NETASSIST
;PORT=20001
;PACKLEN=1024
========================================================
I've added a MAX7320 i2c expander chip to i2c bus 0 on my ARM Linux board.
The chip works correctly from userspace with commands such as /usr/sbin/i2cset -y 0 0x5d 0x02 and /usr/sbin/i2cget -y 0 0x5d.
There is a drivers/gpio/gpio-max732x.c file in the kernel source, which is compiled into the kernel that I'm running. (I've built it from source.)
How do I tell the kernel that it should instantiate the gpio-max732x driver on "i2c bus 0, chip id 0x5d"?
Do I need to modify the device tree .dts file and put a new .dtb file in /boot/dtbs/?
What would the clause for instantiating a gpio-max732x module look like?
P.S. I've seen https://lkml.org/lkml/2015/1/13/305 but I can't figure out how to get the patch files.
Device Tree
There must be appropriate Device Tree definition for your chip, in order for driver to instantiate. There are 2 ways to do so:
Modify .dts Device Tree file for your board (look in arch/arm/boot/dts/), then recompile it and re-flash it to your device.
This way is preferred in case when you have access you kernel sources for your board and you are able to re-flash .dtb file to your device.
Create Device Tree Overlay file, compile it and load it on your device.
This way is preferred when you don't have access to kernel sources for your board, or you are unable to flash new device tree blob to your device.
Your device definition in Device Tree should look like (according to Documentation/devicetree/bindings/gpio/gpio-max732x.txt):
&i2c0 {
expander: max7320#5d {
compatible = "maxim,max7320";
reg = <0x5d>;
gpio-controller;
#gpio-cells = <2>;
};
};
Kernel configuration
As your expander chip (MAX7320) has no input GPIOs, you don't need IRQ support for MAX732x. So you can disable CONFIG_GPIO_MAX732X_IRQ in your kernel configuration.
Matching device with driver
Once you have your Device Tree loaded (with definition for MAX7320), MAX732x driver will be matched with device definition, and instantiated. Below is explained how matching happens.
In Device Tree file you have compatible property:
compatible = "maxim,max7320";
In MAX732x driver you can see this table:
static const struct of_device_id max732x_of_table[] = {
...
{ .compatible = "maxim,max7320" },
...
When driver is being loaded, and when Device Tree blob is being loaded, kernel tries to find the match for each driver and Device Tree definition. Just by comparing strings above. If strings are matched -- kernel instantiates driver, passing corresponding device parameters to it. Look at i2c_device_match() function for details.
Obtaining patches
The best way is to use kernel sources that already have Device Tree support of MAX732x (v4.0+). But if it's not the case, then...
You can cherry-pick patches from upstream kernel to your kernel:
$ git remote add upstream git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ git fetch --all
$ git cherry-pick 43c4bcf9425e
$ git cherry-pick 479f8a5744d8
$ git cherry-pick 09afa276d52e
$ git cherry-pick 996bd13f28e6
And if you still want to apply patches manually (worst option, actually), here you can find direct links to patches. Click (patch) link to get a raw patch.
Also check later patches for gpio-max732x.c here.
Hardware concerns
To be sure that your chip has 0x5d I2C address, check that configuration pins are tied to next lines (as per datasheet):
Pin Line
-----------
AD2 V+
AD0 V+
I'm working with MDK-Pro and the File System library.
In my application, I require an SPI interface to the SD card. I've managed to setup the project properly, except that in the RTE_Components.h file that Keil generates the line #define RTE_Drivers_MCI0 which subsequently triggers a preprocessor error ("SDIO not configured in RTE_Device.h").
Although I can manually comment out this line in RTE_Components.h, every so often Keil updates this file and I get the above problem. Does anyone know what exactly generates this file, and how I can stop it from adding the SDIO-related definitions into the project?
The RTE_Components.h is not supposed to be modified and will always be automatically generated. That the stack tries to connect via MCI interface is related to your configuration made in the "FS_Config_MC_0.h".
// <o>Connect to hardware via Driver_MCI# <0-255>
// <i>Select driver control block for hardware interface
#define MC0_MCI_DRIVER 0
// <o>Connect to hardware via Driver_SPI# <0-255>
// <i>Select driver control block for hardware interface when in SPI mode
#define MC0_SPI_DRIVER 0
// <o>Memory Card Interface Mode <0=>Native <1=>SPI
// <i>Native uses a SD Bus with up to 8 data lines, CLK, and CMD
// <i>SPI uses 2 data lines (MOSI and MISO), SCLK and CS
// <i>When using SPI both Driver_SPI# and Driver_MCI# must be specified
// <i>since the MCI driver provides the control interface lines.
#define MC0_SPI 1