1How to port a serial driver to driver model
2===========================================
3
4Almost all of the serial drivers have been converted as at January 2016. These
5ones remain:
6
7   serial_bfin.c
8   serial_pxa.c
9
10The deadline for this work was the end of January 2016. If no one steps
11forward to convert these, at some point there may come a patch to remove them!
12
13Here is a suggested approach for converting your serial driver over to driver
14model. Please feel free to update this file with your ideas and suggestions.
15
16- #ifdef out all your own serial driver code (#ifndef CONFIG_DM_SERIAL)
17- Define CONFIG_DM_SERIAL for your board, vendor or architecture
18- If the board does not already use driver model, you need CONFIG_DM also
19- Your board should then build, but will not boot since there will be no serial
20    driver
21- Add the U_BOOT_DRIVER piece at the end (e.g. copy serial_s5p.c for example)
22- Add a private struct for the driver data - avoid using static variables
23- Implement each of the driver methods, perhaps by calling your old methods
24- You may need to adjust the function parameters so that the old and new
25    implementations can share most of the existing code
26- If you convert all existing users of the driver, remove the pre-driver-model
27    code
28
29In terms of patches a conversion series typically has these patches:
30- clean up / prepare the driver for conversion
31- add driver model code
32- convert at least one existing board to use driver model serial
33- (if no boards remain that don't use driver model) remove the old code
34
35This may be a good time to move your board to use device tree also. Mostly
36this involves these steps:
37
38- define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
39- add your device tree files to arch/<arch>/dts
40- update the Makefile there
41- Add stdout-path to your /chosen device tree node if it is not already there
42- build and get u-boot-dtb.bin so you can test it
43- Your drivers can now use device tree
44- For device tree in SPL, define CONFIG_SPL_OF_CONTROL
45