在调试中加入debugfs有时可以起到事半功倍的效果：
adb shell
#mkdir /data/debug
#mount -t debugfs debugfs /data/debug
#cd /data/debug
查看gpio状态
root@android:/data/debugfs # cat gpio
GPIOs 0-15:
gpio-0 (front_camera_rst ) out lo
GPIOs 16-42:
gpio-17 (tsl2771_int ) in hi
gpio-26 (ctp_reset ) out hi
gpio-29 (front_camera_pwd ) out hi
gpio-31 (gpio_kp_out ) out lo
gpio-32 (gpio_kp_out ) out lo
gpio-35 (GPIO_E186_POWER ) in lo
gpio-36 (gpio_kp_in ) in hi
gpio-37 (gpio_kp_in ) in hi
gpio-42 (hs_sw ) in hi
GPIOs 43-67:
gpio-48 (ctp_irq ) in hi
gpio-60 (qup_scl ) in hi
gpio-61 (qup_sda ) in hi
GPIOs 68-94:
gpio-76 (lis3dh_acc_int ) in lo
gpio-82 ([auto] ) out hi
gpio-85 (bahama sys_rst_n ) in lo
gpio-94 ([auto] ) out hi
GPIOs 95-106:
gpio-97 (MDP_VSYNC ) in lo
GPIOs 107-132:
gpio-107 (ctp_power ) in hi
gpio-115 (GPIO_E186_WAKEUP ) in lo
gpio-131 (qup_scl ) in hi
gpio-132 (qup_sda ) in hi
查看regulator
root@android:/data/debugfs # cd
regulator/
dummy/ ldo03/ ldo06/ ldo09/ ldo12/ ldo15/ ldo18/ smps1/ smps4/
ldo01/ ldo04/ ldo07/ ldo10/ ldo13/ ldo16/ ldo19/ smps2/
ldo02/ ldo05/ ldo08/ ldo11/ ldo14/ ldo17/ ncp/ smps3/
root@android:/data/debugfs # cat
regulator/ldo10/voltage
3000000
查看clk
root@android:/ #
cat /data/debugfs/clk/
adm_clk/ ebi_mddi_clk/
sdc1_p_clk/
adsp_clk/ ebi_vfe_clk/
sdc2_clk/
ahb_m_clk/ ecodec_clk/
sdc2_p_clk/
ahb_s_clk/ gp_clk/
sdc3_clk/
cam_m_clk/ grp_3d_clk/
sdc3_p_clk/
csi0_clk/ grp_3d_p_clk/
sdc4_clk/
csi0_p_clk/ gsbi1_qup_clk/
sdc4_p_clk/
csi0_vfe_clk/ gsbi1_qup_p_clk/
tsif_p_clk/
csi1_clk/ gsbi2_qup_clk/
tsif_ref_clk/
csi1_p_clk/ gsbi2_qup_p_clk/
uart1_clk/
csi1_vfe_clk/ icodec_rx_clk/
uart1dm_clk/
debug_suspend icodec_tx_clk/
uart2_clk/
dsi_byte_clk/ imem_clk/
uart2dm_clk/
dsi_clk/ mdp_clk/
usb_hs2_clk/
dsi_esc_clk/ mdp_dsi_p_clk/
usb_hs_clk/
dsi_pixel_clk/ mdp_lcdc_pad_pclk_clk/
usb_hs_core_clk/
dsi_ref_clk/ mdp_lcdc_pclk_clk/
usb_hs_p_clk/
ebi1_clk/ mdp_vsync_clk/
usb_phy_clk/
ebi2_clk/ pbus_clk/
vdc_clk/
ebi_acpu_clk/ pcm_clk/
vfe_clk/
ebi_adm_clk/ pmdh_clk/
vfe_mdc_clk/
ebi_grp_3d_clk/ sdac_clk/
ebi_lcdc_clk/ sdc1_clk/
root@android:/ #
cat /data/debugfs/clk/mdp_clk/rate
200000000