1. Introduction[edit source]
Debugfs is a simple-to-use RAM-based file system, specially designed for debugging purposes.
It is provided as a simple way for kernel developers to make information available to the user space.
It is part of a pseudo filesystem. Unlike procfs, which is only meant for process information, or sysfs, which has strict one-value-per-file rules, debugfs has no rules at all.
Developers are free to put any information into debugfs.
2. Installing debugfs on your target board[edit source]
Debugfs is enabled and ready to be used in all STM32MPU Embedded Software distributions, via the Linux® kernel configuration CONFIG_DEBUG_FS, set to yes by default.
Symbol: DEBUG_FS Location: Kernel Hacking ---> Compile-time checks and compiler options --> [*] Debug Filesystem
Please refer to the Menuconfig or how to configure kernel article for instructions on modifying the configuration and recompiling the Linux kernel image in the distribution package context.
3. Getting started[edit source]
3.1. How to mount debugfs[edit source]
Debugfs is typically mounted at /sys/kernel/debug with a command such as:
mount -t debugfs none /sys/kernel/debug
3.2. How to use debugfs in Linux kernel drivers[edit source]
Debugfs is a simple way for kernel drivers to make information available to user space.
It can be manipulated using several calls from the C header file include/linux/debugfs.h , such as:
debugfs_create_file → for creating a file in the debug filesystem. debugfs_create_dir → for creating a directory in the debug filesystem. debugfs_create_symlink → for creating a symbolic link in the debug filesystem. debugfs_create_u32 → for creating a file containing a single 32-bit unsigned integer value debugfs_remove → for removing a debugfs entry from the debug filesytem. ...
For further details, refer to the Linux kernel documentation for debugfs[1].
For example, you can refer to an OpenSourceForU article: [2].
3.3. How to visualize debugfs information[edit source]
On the target board, go the debugfs mount directory:
cd /sys/kernel/debug
There you will find all the debugfs entries created by Linux kernel frameworks
ls -l
drwxr-xr-x 2 root root 0 Jan 1 1970 49000000.usb-otg drwxr-xr-x 4 root root 0 Jan 1 1970 asoc drwxr-xr-x 40 root root 0 Jan 1 1970 bdi drwxr-xr-x 10 root root 0 Jan 1 1970 block drwxr-xr-x 2 root root 0 Jan 1 1970 bluetooth drwxr-xr-x 3 root root 0 May 28 15:52 cec drwxr-xr-x 225 root root 0 Jan 1 1970 clk drwxr-xr-x 2 root root 0 Jan 1 1970 dma_buf drwxr-xr-x 3 root root 0 Jan 1 1970 dri drwxr-xr-x 2 root root 0 Jan 1 1970 dynamic_debug drwxr-xr-x 2 root root 0 Jan 1 1970 extfrag -rw-r--r-- 1 root root 0 Jan 1 1970 fault_around_bytes drwxr-xr-x 3 root root 0 May 28 15:52 gc -r--r--r-- 1 root root 0 Jan 1 1970 gpio drwxr-xr-x 2 root root 0 Jan 1 1970 hid drwxr-xr-x 2 root root 0 Jan 1 1970 ieee80211 drwxr-xr-x 7 root root 0 Jan 1 1970 iio -r--r--r-- 1 root root 0 Jan 1 1970 irq_domain_mapping drwxr-xr-x 2 root root 0 Jan 1 1970 memblock drwxr-xr-x 3 root root 0 Jan 1 1970 mmc0 drwxr-xr-x 3 root root 0 Jan 1 1970 mmc1 drwxr-xr-x 11 root root 0 Jan 1 1970 mtd drwxr-xr-x 4 root root 0 Jan 1 1970 pinctrl drwxr-xr-x 4 root root 0 Jan 1 1970 pm_genpd drwxr-xr-x 2 root root 0 Jan 1 1970 pm_qos -r--r--r-- 1 root root 0 Jan 1 1970 pwm drwxr-xr-x 2 root root 0 Jan 1 1970 ras drwxr-xr-x 13 root root 0 Jan 1 1970 regmap drwxr-xr-x 21 root root 0 Jan 1 1970 regulator drwxr-xr-x 3 root root 0 Jan 1 1970 remoteproc -r--r--r-- 1 root root 0 Jan 1 1970 sleep_time drwxr-xr-x 3 root root 0 Jan 1 1970 stmmaceth -r--r--r-- 1 root root 0 Jan 1 1970 suspend_stats dr-xr-xr-x 3 root root 0 Jan 1 1970 tracing drwxr-xr-x 2 root root 0 Jan 1 1970 ubi drwxr-xr-x 2 root root 0 Jan 1 1970 ubifs drwxr-xr-x 4 root root 0 Jan 1 1970 usb -r--r--r-- 1 root root 0 Jan 1 1970 wakeup_sources
You can then browse to find the requested information.
Please note that the different Linux software frameworks available in STM32 MPU Linux kernel overview provide specific trace and debug information in a "How to trace and debug the framework" dedicated chapter, incuding debugfs.
Some examples:
- To list the wakeup sources:
cat /sys/kernel/debug/wakeup_sources name active_count event_count wakeup_count expire_count active_since total_time max_time last_change prevent_suspend_time 5c002000.i2c:stpmu1@33:onkey 0 0 0 0 0 0 0 4075 0 0-0033 0 0 0 0 0 0 0 3949 0 alarmtimer 0 0 0 0 0 0 0 3901 0 5c004000.rtc 1 1 0 0 0 0 0 5246 0 deleted 0 0 0 0 0 0 0 0 0
- To obtain a summary of the clock settings:
cat /sys/kernel/debug/clk/clk_summary
clock enable_cnt prepare_cnt rate accuracy phase
----------------------------------------------------------------------------------------
ck_usbo_48m 1 1 48000000 0 0
usbo_k 1 1 48000000 0 0
ck_dsi_phy 1 1 0 0 0
dsi_k 1 1 0 0 0
i2s_ckin 0 0 0 0 0
clk-csi 1 1 4000000 0 0
ck_csi 1 1 4000000 0 0
rng2_k 0 0 4000000 0 0
rng1_k 0 0 4000000 0 0
clk-lsi 1 1 32000 0 0
ck_lsi 1 1 32000 0 0
dac12_k 0 0 32000 0 0
clk-lse 1 1 32768 0 0
ck_lse 1 1 32768 0 0
ck_rtc 2 2 32768 0 0
rtc_lsco 1 1 32768 0 0
lptim5_k 0 0 32768 0 0
lptim4_k 0 0 32768 0 0
cec_k 0 0 32768 0 0
clk-hsi 1 1 64000000 0 0
clk-hsi-div 1 1 64000000 0 0
ck_hsi 2 2 64000000 0 0
ck_mco1 0 0 64000000 0 0
uart8_k 0 0 64000000 0 0
uart7_k 0 0 64000000 0 0
uart6_k 0 0 64000000 0 0
uart5_k 0 0 64000000 0 0
uart4_k 1 1 64000000 0 0
usart3_k 0 0 64000000 0 0
usart2_k 1 1 64000000 0 0
usart1_k 0 0 64000000 0 0
i2c6_k 0 0 64000000 0 0
i2c4_k 0 0 64000000 0 0
i2c5_k 0 0 64000000 0 0
i2c3_k 0 0 64000000 0 0
i2c2_k 0 0 64000000 0 0
i2c1_k 0 0 64000000 0 0
spi6_k 0 0 64000000 0 0
spi5_k 0 0 64000000 0 0
spi4_k 0 0 64000000 0 0
clk-hse 1 1 24000000 0 0
ck_hse 7 7 24000000 0 0
ck_hse_rtc 0 0 1000000 0 0
stgen_k 1 1 24000000 0 0
usbphy_k 1 1 24000000 0 0
ck_per 1 1 24000000 0 0
adc12_k 1 1 24000000 0 0
ref4 1 1 24000000 0 0
pll4 1 1 594000000 0 0
pll4_r 0 0 74250000 0 0
pll4_q 1 1 31263158 0 0
ltdc_px 1 1 31263158 0 0
dsi_px 0 0 31263158 0 0
fdcan_k 0 0 31263158 0 0
pll4_p 0 0 74250000 0 0
ref3 1 1 24000000 0 0
pll3 2 3 786431640 0 0
pll3_r 1 1 98303955 0 0
sdmmc3_k 0 0 98303955 0 0
sdmmc2_k 1 1 98303955 0 0
sdmmc1_k 0 0 98303955 0 0
pll3_q 0 1 49151978 0 0
adfsdm_k 0 0 49151978 0 0
sai4_k 0 0 49151978 0 0
sai3_k 0 0 49151978 0 0
sai2_k 0 2 49151978 0 0
sai1_k 0 0 49151978 0 0
spi3_k 0 0 49151978 0 0
spi2_k 0 0 49151978 0 0
spi1_k 0 0 49151978 0 0
spdif_k 0 0 49151978 0 0
pll3_p 1 1 196607910 0 0
ck_mcu 6 16 196607910 0 0
dfsdm_k 0 0 196607910 0 0
gpiok 0 0 196607910 0 0
gpioj 0 0 196607910 0 0
gpioi 0 1 196607910 0 0
gpioh 0 1 196607910 0 0
gpiog 0 1 196607910 0 0
gpiof 0 1 196607910 0 0
gpioe 0 1 196607910 0 0
gpiod 0 1 196607910 0 0
gpioc 0 1 196607910 0 0
gpiob 0 1 196607910 0 0
gpioa 0 1 196607910 0 0
ipcc 2 2 196607910 0 0
hsem 0 0 196607910 0 0
crc2 0 0 196607910 0 0
rng2 0 0 196607910 0 0
hash2 0 0 196607910 0 0
cryp2 0 0 196607910 0 0
dcmi 0 0 196607910 0 0
sdmmc3 0 0 196607910 0 0
usbo 0 0 196607910 0 0
adc12 1 1 196607910 0 0
dmamux 1 1 196607910 0 0
dma2 0 0 196607910 0 0
dma1 1 1 196607910 0 0
pclk3 1 1 98303955 0 0
lptim3_k 0 0 98303955 0 0
lptim2_k 0 0 98303955 0 0
hdp 0 0 98303955 0 0
pmbctrl 0 0 98303955 0 0
tmpsens 0 0 98303955 0 0
vref 0 0 98303955 0 0
syscfg 1 1 98303955 0 0
sai4 0 0 98303955 0 0
lptim5 0 0 98303955 0 0
lptim4 0 0 98303955 0 0
lptim3 0 0 98303955 0 0
lptim2 0 0 98303955 0 0
pclk2 0 0 98303955 0 0
fdcan 0 0 98303955 0 0
dfsdm 0 0 98303955 0 0
sai3 0 0 98303955 0 0
sai2 0 0 98303955 0 0
sai1 0 0 98303955 0 0
usart6 0 0 98303955 0 0
spi5 0 0 98303955 0 0
spi4 0 0 98303955 0 0
spi1 0 0 98303955 0 0
tim17 0 0 98303955 0 0
tim16 0 0 98303955 0 0
tim15 0 0 98303955 0 0
tim8 0 0 98303955 0 0
tim1 0 0 98303955 0 0
ck2_tim 0 0 196607910 0 0
tim17_k 0 0 196607910 0 0
tim16_k 0 0 196607910 0 0
tim15_k 0 0 196607910 0 0
tim8_k 0 0 196607910 0 0
tim1_k 0 0 196607910 0 0
pclk1 0 2 98303955 0 0
lptim1_k 0 0 98303955 0 0
mdio 0 0 98303955 0 0
dac12 0 0 98303955 0 0
cec 0 0 98303955 0 0
spdif 0 0 98303955 0 0
i2c5 0 0 98303955 0 0
i2c3 0 0 98303955 0 0
i2c2 0 0 98303955 0 0
i2c1 0 0 98303955 0 0
uart8 0 0 98303955 0 0
uart7 0 0 98303955 0 0
uart5 0 0 98303955 0 0
uart4 0 0 98303955 0 0
usart3 0 0 98303955 0 0
usart2 0 0 98303955 0 0
spi3 0 0 98303955 0 0
spi2 0 1 98303955 0 0
lptim1 0 0 98303955 0 0
tim14 0 0 98303955 0 0
tim13 0 0 98303955 0 0
tim12 0 0 98303955 0 0
tim7 0 0 98303955 0 0
tim6 0 0 98303955 0 0
tim5 0 0 98303955 0 0
tim4 0 0 98303955 0 0
tim3 0 0 98303955 0 0
tim2 0 0 98303955 0 0
ck1_tim 0 1 196607910 0 0
tim14_k 0 0 196607910 0 0
tim13_k 0 0 196607910 0 0
tim12_k 0 0 196607910 0 0
tim7_k 0 0 196607910 0 0
tim6_k 0 1 196607910 0 0
tim5_k 0 0 196607910 0 0
tim4_k 0 0 196607910 0 0
tim3_k 0 0 196607910 0 0
tim2_k 0 0 196607910 0 0
ref1 2 2 24000000 0 0
pll2 2 2 533000000 0 0
pll2_r 1 1 533000000 0 0
pll2_q 0 0 533000000 0 0
gpu_k 0 0 533000000 0 0
pll2_p 1 1 266500000 0 0
ck_axi 8 9 266500000 0 0
ck_trace 0 0 133250000 0 0
ck_sys_dbg 0 0 266500000 0 0
qspi_k 0 0 266500000 0 0
fmc_k 0 0 266500000 0 0
ethstp 0 0 266500000 0 0
usbh 1 1 266500000 0 0
crc1 0 0 266500000 0 0
sdmmc2 0 0 266500000 0 0
sdmmc1 0 0 266500000 0 0
qspi 0 0 266500000 0 0
fmc 0 0 266500000 0 0
ethmac 1 1 266500000 0 0
ethrx 1 1 266500000 0 0
ethtx 1 1 266500000 0 0
gpu 0 0 266500000 0 0
mdma 1 1 266500000 0 0
bkpsram 0 0 266500000 0 0
rng1 0 0 266500000 0 0
hash1 0 0 266500000 0 0
cryp1 0 0 266500000 0 0
gpioz 0 1 266500000 0 0
tzc2 0 0 266500000 0 0
tzc1 0 0 266500000 0 0
pclk5 1 1 66625000 0 0
stgen 0 0 66625000 0 0
bsec 0 0 66625000 0 0
iwdg1 0 0 66625000 0 0
tzpc 0 0 66625000 0 0
rtcapb 2 2 66625000 0 0
usart1 0 0 66625000 0 0
i2c6 0 0 66625000 0 0
i2c4 0 0 66625000 0 0
spi6 0 0 66625000 0 0
pclk4 1 1 133250000 0 0
stgenro 0 0 133250000 0 0
usbphy 0 0 133250000 0 0
iwdg2 1 1 133250000 0 0
dsi 0 0 133250000 0 0
ltdc 0 0 133250000 0 0
pll1 1 1 650000000 0 0
pll1_p 1 1 650000000 0 0
ck_mpu 1 1 650000000 0 0
ck_mco2 0 0 650000000 0 0
clk-hse-div2 0 0 12000000 0 0
ethptp_k 0 0 0 0 0
ethck_k 0 0 0 0 0
- To obtain a summary of the regulator settings:
cat /sys/kernel/debug/regulator/regulator_summary
regulator use open bypass voltage current min max
-------------------------------------------------------------------------------
regulator-dummy 0 11 0 0mV 0mA 0mV 0mV
49000000.usb-otg 0mV 0mV
49000000.usb-otg 0mV 0mV
5a000000.dsi.0 0mV 0mV
vddcore 0 0 0 1200mV 0mA 800mV 1350mV
vdd_ddr 0 1 0 1350mV 0mA 1350mV 1350mV
vtt_ddr 0 0 0 675mV 0mA 675mV 675mV
vdd 0 1 0 3300mV 0mA 3300mV 3300mV
vref 1 1 0 2500mV 0mA 2500mV 2500mV
48003000.adc 0mV 0mV
v3v3 0 5 0 3300mV 0mA 3300mV 3300mV
0-004a 0mV 0mV
58007000.sdmmc 3300mV 3300mV
58005000.sdmmc 3300mV 3300mV
v1v8_audio 0 3 0 1800mV 0mA 1800mV 1800mV
0-004a 0mV 0mV
0-004a 0mV 0mV
0-004a 0mV 0mV
v1v2_hdmi 0 1 0 1200mV 0mA 1200mV 1200mV
0-0039 0mV 0mV
v3v3_hdmi 0 1 0 3300mV 0mA 3300mV 3300mV
0-0039 0mV 0mV
vdd_usb 2 2 0 3300mV 0mA 3300mV 3300mV
phy-5a006000.usbphyc.1 0mV 0mV
phy-5a006000.usbphyc.0 0mV 0mV
vdda 0 0 0 2900mV 0mA 2900mV 2900mV
bst_out 0 2 0 5000mV 0mA 0mV 0mV
vbus_otg 0 0 0 5000mV 0mA 0mV 0mV
vbus_sw 0 0 0 5000mV 0mA 0mV 0mV
reg11 1 1 0 1100mV 0mA 1100mV 1100mV
5a006000.usbphyc 0mV 0mV
reg18 2 2 0 1800mV 0mA 1800mV 1800mV
5a006000.usbphyc 0mV 0mV
5a000000.dsi 0mV 0mV
usb33 1 1 0 3300mV 0mA 3300mV 3300mV
49000000.usb-otg 0mV 0mV
vref_ddr 0 0 0 675mV 0mA 0mV 0mV
- To list the pin control settings:
cat /sys/kernel/debug/pinctrl/soc\:pin*@50002000/pinconf-pins Pin config settings per pin Format: pin (name): configs pin 0 (PA0): analog pin 1 (PA1): alternate 11 (ETH1_GMII_RX_CLK ETH1_MII_RX_CLK ETH1_RGMII_RX_CLK ETH1_RMII_REF_CLK) - push pull - floating - low speed pin 2 (PA2): alternate 11 (ETH1_MDIO) - push pull - floating - very high speed pin 3 (PA3): alternate 14 (LCD_B5) - push pull - floating - high speed pin 4 (PA4): analog pin 5 (PA5): analog pin 6 (PA6): analog pin 7 (PA7): alternate 11 (ETH1_GMII_RX_DV ETH1_MII_RX_DV ETH1_RGMII_RX_CTL ETH1_RMII_CRS_DV) - push pull - floating - low speed pin 8 (PA8): analog pin 9 (PA9): analog pin 10 (PA10): output - high - push pull - floating - low speed pin 11 (PA11): analog pin 12 (PA12): analog pin 13 (PA13): output - low - open drain - floating - very high speed pin 14 (PA14): input - high - floating pin 15 (PA15): analog pin 16 (PB0): alternate 11 (ETH1_GMII_RXD2 ETH1_MII_RXD2 ETH1_RGMII_RXD2) - push pull - floating - low speed pin 17 (PB1): alternate 11 (ETH1_GMII_RXD3 ETH1_MII_RXD3 ETH1_RGMII_RXD3) - push pull - floating - low speed pin 18 (PB2): alternate 8 (UART4_RX) - push pull - floating - low speed pin 19 (PB3): alternate 9 (SDMMC2_D2) - push pull - pull up - very high speed pin 20 (PB4): alternate 9 (SDMMC2_D3) - push pull - pull up - very high speed pin 21 (PB5): analog pin 22 (PB6): alternate 5 (CEC) - open drain - floating - low speed pin 23 (PB7): analog pin 24 (PB8): alternate 14 (LCD_B6) - push pull - floating - high speed pin 25 (PB9): analog pin 26 (PB10): analog pin 27 (PB11): alternate 11 (ETH1_GMII_TX_EN ETH1_MII_TX_EN ETH1_RGMII_TX_CTL ETH1_RMII_TX_EN) - push pull - floating - very high speed pin 28 (PB12): analog pin 29 (PB13): analog pin 30 (PB14): alternate 9 (SDMMC2_D0) - push pull - pull up - very high speed pin 31 (PB15): alternate 9 (SDMMC2_D1) - push pull - pull up - very high speed pin 32 (PC0): alternate 14 (LCD_R5) - push pull - floating - high speed pin 33 (PC1): alternate 11 (ETH1_MDC) - push pull - floating - very high speed pin 34 (PC2): alternate 11 (ETH1_GMII_TXD2 ETH1_MII_TXD2 ETH1_RGMII_TXD2) - push pull - floating - very high speed pin 35 (PC3): analog pin 36 (PC4): alternate 11 (ETH1_GMII_RXD0 ETH1_MII_RXD0 ETH1_RGMII_RXD0 ETH1_RMII_RXD0) - push pull - floating - low speed pin 37 (PC5): alternate 11 (ETH1_GMII_RXD1 ETH1_MII_RXD1 ETH1_RGMII_RXD1 ETH1_RMII_RXD1) - push pull - floating - low speed pin 38 (PC6): analog pin 39 (PC7): analog pin 40 (PC8): analog pin 41 (PC9): analog pin 42 (PC10): analog pin 43 (PC11): analog pin 44 (PC12): analog pin 45 (PC13): analog pin 46 (PC14): analog pin 47 (PC15): analog pin 48 (PD0): analog pin 49 (PD1): analog pin 50 (PD2): analog pin 51 (PD3): alternate 7 (USART2_CTS USART2_NSS) - push pull - floating - low speed pin 52 (PD4): alternate 7 (USART2_RTS USART2_DE) - push pull - floating - very high speed pin 53 (PD5): alternate 7 (USART2_TX) - push pull - floating - very high speed pin 54 (PD6): alternate 7 (USART2_RX) - push pull - floating - low speed pin 55 (PD7): analog pin 56 (PD8): alternate 14 (LCD_B7) - push pull - floating - high speed pin 57 (PD9): alternate 14 (LCD_B0) - push pull - floating - high speed pin 58 (PD10): alternate 14 (LCD_B3) - push pull - floating - high speed pin 59 (PD11): output - low - push pull - floating - low speed pin 60 (PD12): alternate 5 (I2C1_SCL) - open drain - floating - low speed pin 61 (PD13): analog pin 62 (PD14): analog pin 63 (PD15): analog pin 64 (PE0): alternate 10 (SAI2_MCLK_A) - push pull - floating - high speed pin 65 (PE1): analog pin 66 (PE2): alternate 11 (ETH1_GMII_TXD3 ETH1_MII_TXD3 ETH1_RGMII_TXD3) - push pull - floating - very high speed pin 67 (PE3): alternate 9 (SDMMC2_CK) - push pull - pull up - very high speed pin 68 (PE4): output - high - push pull - floating - low speed pin 69 (PE5): alternate 14 (LCD_G0) - push pull - floating - high speed pin 70 (PE6): alternate 14 (LCD_G1) - push pull - floating - high speed pin 71 (PE7): analog pin 72 (PE8): analog pin 73 (PE9): analog pin 74 (PE10): analog pin 75 (PE11): analog pin 76 (PE12): analog pin 77 (PE13): analog pin 78 (PE14): analog pin 79 (PE15): alternate 14 (LCD_R7) - push pull - floating - high speed pin 80 (PF0): analog pin 81 (PF1): analog pin 82 (PF2): input - high - floating pin 83 (PF3): analog pin 84 (PF4): analog pin 85 (PF5): analog pin 86 (PF6): analog pin 87 (PF7): analog pin 88 (PF8): analog pin 89 (PF9): analog pin 90 (PF10): alternate 14 (LCD_DE) - push pull - floating - high speed pin 91 (PF11): alternate 10 (SAI2_SD_B) - push pull - floating - low speed pin 92 (PF12): analog pin 93 (PF13): analog pin 94 (PF14): analog pin 95 (PF15): alternate 5 (I2C1_SDA) - open drain - floating - low speed pin 96 (PG0): analog pin 97 (PG1): input - high - floating pin 98 (PG2): analog pin 99 (PG3): analog pin 100 (PG4): alternate 11 (ETH1_GMII_GTX_CLK ETH1_RGMII_GTX_CLK) - push pull - floating - very high speed pin 101 (PG5): alternate 11 (ETH1_GMII_CLK125 ETH1_RGMII_CLK125) - push pull - floating - very high speed pin 102 (PG6): alternate 10 (SDMMC2_CMD) - push pull - pull up - very high speed pin 103 (PG7): alternate 14 (LCD_CLK) - push pull - floating - high speed pin 104 (PG8): analog pin 105 (PG9): output - high - push pull - floating - low speed pin 106 (PG10): alternate 14 (LCD_B2) - push pull - floating - high speed pin 107 (PG11): alternate 6 (UART4_TX) - push pull - floating - low speed pin 108 (PG12): alternate 14 (LCD_B1) - push pull - floating - high speed pin 109 (PG13): alternate 11 (ETH1_GMII_TXD0 ETH1_MII_TXD0 ETH1_RGMII_TXD0 ETH1_RMII_TXD0) - push pull - floating - very high speed pin 110 (PG14): alternate 11 (ETH1_GMII_TXD1 ETH1_MII_TXD1 ETH1_RGMII_TXD1 ETH1_RMII_TXD1) - push pull - floating - very high speed pin 111 (PG15): analog pin 112 (PH0): analog pin 113 (PH1): analog pin 114 (PH2): alternate 14 (LCD_R0) - push pull - floating - high speed pin 115 (PH3): alternate 14 (LCD_R1) - push pull - floating - high speed pin 116 (PH4): output - high - push pull - floating - low speed pin 117 (PH5): analog pin 118 (PH6): analog pin 119 (PH7): analog pin 120 (PH8): alternate 14 (LCD_R2) - push pull - floating - high speed pin 121 (PH9): alternate 14 (LCD_R3) - push pull - floating - high speed pin 122 (PH10): alternate 14 (LCD_R4) - push pull - floating - high speed pin 123 (PH11): analog pin 124 (PH12): alternate 14 (LCD_R6) - push pull - floating - high speed pin 125 (PH13): alternate 14 (LCD_G2) - push pull - floating - high speed pin 126 (PH14): alternate 14 (LCD_G3) - push pull - floating - high speed pin 127 (PH15): alternate 14 (LCD_G4) - push pull - floating - high speed pin 128 (PI0): alternate 14 (LCD_G5) - push pull - floating - high speed pin 129 (PI1): alternate 14 (LCD_G6) - push pull - floating - high speed pin 130 (PI2): alternate 14 (LCD_G7) - push pull - floating - high speed pin 131 (PI3): analog pin 132 (PI4): alternate 14 (LCD_B4) - push pull - floating - high speed pin 133 (PI5): alternate 10 (SAI2_SCK_A) - push pull - floating - medium speed pin 134 (PI6): alternate 10 (SAI2_SD_A) - push pull - floating - medium speed pin 135 (PI7): alternate 10 (SAI2_FS_A) - push pull - floating - medium speed pin 136 (PI8): analog pin 137 (PI9): alternate 14 (LCD_VSYNC) - push pull - floating - high speed pin 138 (PI10): alternate 14 (LCD_HSYNC) - push pull - floating - high speed pin 139 (PI11): analog
- To obtain the GPIO settings (example):
cat /sys/kernel/debug/gpio gpiochip0: GPIOs 0-15, parent: platform/soc:pinctrl@50002000, GPIOA: gpio-10 ( |reset ) out lo gpiochip1: GPIOs 16-31, parent: platform/soc:pinctrl@50002000, GPIOB: gpiochip2: GPIOs 32-47, parent: platform/soc:pinctrl@50002000, GPIOC: gpiochip3: GPIOs 48-63, parent: platform/soc:pinctrl@50002000, GPIOD: gpio-59 ( |heartbeat ) out lo gpiochip4: GPIOs 64-79, parent: platform/soc:pinctrl@50002000, GPIOE: gpio-68 ( |reset ) out hi gpiochip5: GPIOs 80-95, parent: platform/soc:pinctrl@50002000, GPIOF: gpiochip6: GPIOs 96-111, parent: platform/soc:pinctrl@50002000, GPIOG: gpio-105 ( |reset ) out hi gpiochip7: GPIOs 112-127, parent: platform/soc:pinctrl@50002000, GPIOH: gpio-116 ( |reset ) out hi gpiochip8: GPIOs 128-143, parent: platform/soc:pinctrl@50002000, GPIOI: gpiochip9: GPIOs 400-415, parent: platform/soc:pinctrl@54004000, GPIOZ:
4. To go further[edit source]
4.1. Regmap (register map) cache[edit source]
Debugfs contains a register cache (mirror) for drivers/peripherals based on regmap API[3].
Regmap is a register map abstraction API of the Linux kernel. It is mainly used for serial bus device drivers (I2C and SPI), but can also be used for internal peripheral drivers.
Many of these drivers contain some very similar code for accessing connected-hardware device registers.
The regmap kernel API proposes a solution which factors out this code from the drivers, saving code and making it much easier to share infrastructure.
- Path of the regmap register cache in debugfs
cd /sys/kernel/debug/regmap
- List of devices for which drivers are based on regmap API:
ls -la . total 0 drwxr-xr-x 18 root root 0 Jan 1 1970 . drwx------ 32 root root 0 Jan 1 1970 .. drwxr-xr-x 2 root root 0 Jan 1 1970 0-001b drwxr-xr-x 2 root root 0 Jan 1 1970 0-0042 drwxr-xr-x 2 root root 0 Jan 1 1970 2-0033 drwxr-xr-x 2 root root 0 Jan 1 1970 40004000.timer drwxr-xr-x 2 root root 0 Jan 1 1970 4000d000.audio-controller drwxr-xr-x 2 root root 0 Nov 30 12:19 40016000.cec drwxr-xr-x 2 root root 0 Jan 1 1970 40017000.dac drwxr-xr-x 2 root root 0 Jan 1 1970 4400b004.audio-controller drwxr-xr-x 2 root root 0 Jan 1 1970 4400b024.audio-controller drwxr-xr-x 2 root root 0 Jan 1 1970 4400d000.dfsdm drwxr-xr-x 2 root root 0 Jan 1 1970 50027004.audio-controller drwxr-xr-x 2 root root 0 Jan 1 1970 dummy-interrupt-controller@5000d000 drwxr-xr-x 2 root root 0 Jan 1 1970 dummy-pwr@50001000 drwxr-xr-x 2 root root 0 Jan 1 1970 dummy-rcc@50000000 drwxr-xr-x 2 root root 0 Jan 1 1970 dummy-syscon@50020000 drwxr-xr-x 2 root root 0 Jan 1 1970 dummy-tamp@5c00a000
- Check for the corresponding driver: example for 2-0033 regmap entry
cat 2-0033/name stpmic1
Then, on the STM32MPU device tree files, you can check for the device, and the corresponding driver
pmic: stpmic@33 {
compatible = "st,stpmic1";
reg = <0x33>;
interrupts-extended = <&exti_pwr 55 IRQ_TYPE_EDGE_FALLING>;
interrupt-controller;
#interrupt-cells = <2>;
status = "okay";
- Regmap entries stating by dummy-
This kind of entry is set when there are no associated /dev entries (devtmpfs).
To find the corresponding node in the device tree, you can look for the suffix name after dummy-:
Example for dummy-interrupt-controller@5000d000
exti: interrupt-controller@5000d000 {
compatible = "st,stm32mp1-exti", "syscon";
interrupt-controller;
#interrupt-cells = <2>;
reg = <0x5000d000 0x400>;
};
- List of registers: example for 2-0033 regmap entry
cat 2-0033/registers
01: 10
02: 00
03: 00
04: 00
05: 60
06: 10
10: 04
11: 00
12: 00
13: 00
14: 00
15: c0
16: 00
17: 00
18: 04
19: 00
1a: 00
1b: 00
1c: 00
1d: 0f
1e: 04
20: 61
21: 79
22: d9
23: d9
24: 01
25: 51
26: 4c
27: 7d
28: 01
29: 51
2a: 25
30: 61
31: 50
32: d9
33: d9
34: 00
35: 24
36: 24
37: 24
38: 01
39: 51
3a: 04
40: 35
50: 00
51: 00
52: 00
53: 80
60: 00
61: 00
62: 00
63: 00
70: 00
71: 00
72: 00
73: 00
80: fc
81: 8f
82: c4
83: cf
90: fc
91: 8f
92: c4
93: cf
a0: 03
a1: 70
a2: 3b
a3: 00
b0: 00
b1: 00
b2: 00
b3: 80
The first column representes the register address, and the second column the register value.
For register definitions, please refer to the device specification.
5. References[edit source]
- Useful external links
| Document link | Document Type | Description |
|---|---|---|
| Wikipedia debugfs | Standard | Wikipedia |
| Guide to debugfs | Standard | Guide |
| regmap: Reducing the Redundancy in Linux Code | Article | Guide |