Hi everyone,
I've finally started looking into the cfb_console.c driver and it's conversion to DM_VIDEO after our initial discussion [1]. Unfortunately I've a bit underestimated the amount of effort that should be done, as mxsfb.c in the Linux mainline obviously pulls the whole core fb subsystem (drivers/video/fbdev/core), which can take a while and frankly I doubt that this is a proper way to do things here.
Taking into account that the deadline for DM_VIDEO conversion is 2019.07, it's unlikely that we will manage to do the full conversions this cfb_console driver and all dependent hw specific drivers in a proper way (where we can provide information about videomodes as properties in a proper nodes in DT).
Currently the init chain for fb stuff in U-boot (on the other hand, in the Linux, hw specific driver is probed initially, then they trigger fb common routines that are needed from `video/fbdev/core`): stdio_add_devices() -> ./common/stdio.c -> drv_video_init () (drivers/cfb_console.c) - > video_hw_init (particular hw backend, which was statically linked at compile time with a proper video_hw_init() implementation, for example look into mxsfb.c)
2 ways of conversion that come to my mind: 1. Start with simple DM wrappers in cfb_console.c, and introduce dumb DT nodes so the device at least can be probed. All video configuration will be stored the same way as before in the U-boot env (for example, "videomode=video=ctfb:x:640,y:480,depth:18,pclk:39722,le:48,ri:16,up:33,lo:10,hs:96,vs:2,sync:0,vmode:0\0"). Then, step by step, driver by driver, we can move some properties to DT and try to sync Linux/U-boot video DT nodes (at least avoid divergence of tree nodes, so Linux/U-boot video-related DT nodes conform to each other). Yes, this is kind of dirty workaround, but at least this something we can start with, and with minimal amount of intrusive changes. 2. Perform full conversion, where everything works the same way as in Linux kernel. Initially I thought that it could be the proper way to go, but taking into account all differences in the implementation of fb in U-boot/Linux (even the way how the drivers are initialized), I think we will just end up pulling the whole big piece from the Linux kernel, that will definitely take a while (especially further support of this code base, testing/fixing issues etc.).
Just to be aware about the amount of effort that should be done:
: u-boot.git$ grep -e CONFIG_CFB_CONSOLE -r ./configs/ ./configs/T1042RDB_PI_SDCARD_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042D4RDB_SDCARD_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042RDB_PI_NAND_SECURE_BOOT_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/nokia_rx51_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042D4RDB_NAND_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042RDB_PI_SPIFLASH_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042RDB_PI_NAND_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042D4RDB_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/T1042RDB_PI_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/eb_cpu5282_internal_defconfig:# CONFIG_CFB_CONSOLE is not set ./configs/T1042D4RDB_SPIFLASH_defconfig:CONFIG_CFB_CONSOLE_ANSI=y ./configs/eb_cpu5282_defconfig:# CONFIG_CFB_CONSOLE is not set ./configs/T1042D4RDB_SECURE_BOOT_defconfig:CONFIG_CFB_CONSOLE_ANSI=y
Additional Kconfig symbols, that depend on CFB_CONSOLE: * VGA_AS_SINGLE_DEVICE * CONSOLE_EXTRA_INFO * CONSOLE_SCROLL_LINES * SYS_CONSOLE_BG_COL * SYS_CONSOLE_FG_COL
Drivers, that don't imply CFG_CONSOLE, but are used alongside with cfb_console.c (kind of particular hw backend driver for fb console): * mxsfb.c * mb862xx.c * sunxi_display.c * ati_radeon_fb.c * fsl_dcu_fb.c * omap3_dss.c * da8xx-fb.c
Looking forward to your suggestions/recommendations here (and let me know if I missed something), thanks!
[1] https://lists.denx.de/pipermail/u-boot/2019-April/365506.html