kernel/firmware: Support RPi GPU, touchscreen

Getting the Raspberry Pi 4 GPU and 7-inch Touch Display 2 working was
quite challenging.  Several kernel drivers are needed, beyond the
obvious VC4 and V3D, like voltage regulators and backlight controls.
Even with all the drivers enabled, I still had trouble getting
`/dev/dri/card1` (the display device, as opposed to `/dev/dri/card0`,
the 3D rendering device) to appear until I explicitly enabled the
`vc4-kms-dsi-ili9881-7inch` device tree overlay.  I am not entirely sure
why this is necessary, since `display_auto_detect` supposedly should
have added this overlay automatically.  I am also not sure how it would
work if I wanted to use an HDMI monitor instead of the DSI panel, but
fortunately, for this project, that's not necessary.

config.txt

@@ -1,12 +1,8 @@
 arm_64bit=1
+arm_boost=1
 
 start_x=1
 
-bootcode_delay=0
-boot_delay=0
-
-gpu_mem=32
-
 kernel=u-boot.bin
 
 enable_uart=1
@@ -14,4 +10,10 @@ dtoverlay=miniuart-bt
 
 dtparam i2c_arm=on
 
-device_tree=bcm2711-rpi-4-b.dtb
+display_auto_detect=1
+dtoverlay=vc4-kms-v3d
+dtoverlay=vc4-kms-dsi-ili9881-7inch
+max_framebuffers=2
+disable_fw_kms_setup=1
+disable_overscan=1
+dtparam=audio=on

linux.config

@@ -45,12 +45,65 @@ CONFIG_IPV6=y
 CONFIG_IPV6_SIT=m
 CONFIG_IPV6_SIT_6RD=m
 
+CONFIG_INPUT_TOUCHSCREEN=y
+CONFIG_TOUCHSCREEN_GOODIX=m
+CONFIG_TOUCHSCREEN_EDT_FT5X06=m
+CONFIG_TOUCHSCREEN_RASPBERRYPI_FW=m
+
+CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_ATTINY=m
+CONFIG_REGULATOR_RASPBERRYPI_TOUCHSCREEN_V2=m
 # CONFIG_MEDIA_CEC_SUPPORT is not set
 # CONFIG_MEDIA_SUPPORT is not set
 
-# CONFIG_SOUND is not set
-# CONFIG_SND is not set
-# CONFIG_SND_SOC is not set
+CONFIG_DRM=m
+CONFIG_DRM_KMS_HELPER=m
+CONFIG_DRM_LOAD_EDID_FIRMWARE=y
+CONFIG_DRM_DISPLAY_HELPER=m
+CONFIG_DRM_GEM_SHMEM_HELPER=m
+CONFIG_DRM_SCHED=m
+CONFIG_DRM_PANEL_SIMPLE=m
+CONFIG_DRM_PANEL_ILITEK_ILI9806E=m
+CONFIG_DRM_PANEL_ILITEK_ILI9881C=m
+CONFIG_DRM_PANEL_RASPBERRYPI_TOUCHSCREEN=y
+CONFIG_DRM_DISPLAY_CONNECTOR=m
+CONFIG_DRM_TOSHIBA_TC358762=m
+CONFIG_DRM_SIMPLE_BRIDGE=m
+CONFIG_DRM_V3D=m
+CONFIG_VC4=m
+CONFIG_DRM_VC4_HDMI_CEC=y
+CONFIG_DRM_RP1_DSI=m
+CONFIG_DRM_RP1_DPI=m
+CONFIG_DRM_RP1_VEC=m
+CONFIG_DRM_PANEL_ORIENTATION_QUIRKS=m
+CONFIG_FB_BCM2708=y
+CONFIG_FB_SIMPLE=y
+CONFIG_FB_SSD1307=m
+CONFIG_FB_RPISENSE=m
+CONFIG_FB_CFB_FILLRECT=y
+CONFIG_FB_CFB_COPYAREA=y
+CONFIG_FB_CFB_IMAGEBLIT=y
+CONFIG_FB_IOMEM_HELPERS=y
+CONFIG_FB_BACKLIGHT=m
+CONFIG_BACKLIGHT_CLASS_DEVICE=m
+CONFIG_BACKLIGHT_PWM=m
+CONFIG_BACKLIGHT_RPI=m
+CONFIG_BACKLIGHT_LM3630A=m
+CONFIG_BACKLIGHT_GPIO=m
+CONFIG_FRAMEBUFFER_CONSOLE_ROTATION=y
+CONFIG_BCM_VC_SM_CMA=m
+
+CONFIG_SOUND=y
+CONFIG_SND=m
+# CONFIG_SND_PCM_TIMER is not set
+# CONFIG_SND_SUPPORT_OLD_API is not set
+# CONFIG_SND_PROC_FS is not set
+# CONFIG_SND_CTL_FAST_LOOKUP is not set
+# CONFIG_SND_DRIVERS is not set
+# CONFIG_SND_PCI is not set
+# CONFIG_SND_SPI is not set
+# CONFIG_SND_USB is not set
+CONFIG_SND_SOC=m
+CONFIG_SND_BCM2835_SOC_I2S=m
 
 CONFIG_AUDIT=y
 CONFIG_SECURITY=y
@@ -64,6 +117,7 @@ CONFIG_MEMCG=y
 CONFIG_CGROUP_PIDS=y
 CONFIG_BLK_CGROUP=y
 
+CONFIG_I2C_HID_OF_GOODIX=m
 CONFIG_USB_DWC2=m
 CONFIG_USB_DWC2_PCI=m
 CONFIG_USB_ACM=m