dm: Add timeline and guide for porting serial drivers
Add a README with a brief guide to porting serial drivers over to use
driver model.
Add a timeline also. All serial drivers should be converted by the end
of January 2016.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/driver-model/serial-howto.txt b/doc/driver-model/serial-howto.txt
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+How to port a serial driver to driver model
+===========================================
+
+About 16 of 33 serial drivers have been converted as at September 2015. It
+is time for maintainers to start converting over the remaining serial drivers:
+
+ altera_jtag_uart.c
+ altera_uart.c
+ arm_dcc.c
+ lpc32xx_hsuart.c
+ mcfuart.c
+ mxs_auart.c
+ opencores_yanu.c
+ serial_bfin.c
+ serial_imx.c
+ serial_lpuart.c
+ serial_max3100.c
+ serial_pxa.c
+ serial_s3c24x0.c
+ serial_sa1100.c
+ serial_stm32.c
+ serial_xuartlite.c
+ usbtty.c
+
+You should complete this by the end of January 2016.
+
+Here is a suggested approach for converting your serial driver over to driver
+model. Please feel free to update this file with your ideas and suggestions.
+
+- #ifdef out all your own serial driver code (#ifndef CONFIG_DM_SERIAL)
+- Define CONFIG_DM_SERIAL for your board, vendor or architecture
+- If the board does not already use driver model, you need CONFIG_DM also
+- Your board should then build, but will not boot since there will be no serial
+ driver
+- Add the U_BOOT_DRIVER piece at the end (e.g. copy serial_s5p.c for example)
+- Add a private struct for the driver data - avoid using static variables
+- Implement each of the driver methods, perhaps by calling your old methods
+- You may need to adjust the function parameters so that the old and new
+ implementations can share most of the existing code
+- If you convert all existing users of the driver, remove the pre-driver-model
+ code
+
+In terms of patches a conversion series typically has these patches:
+- clean up / prepare the driver for conversion
+- add driver model code
+- convert at least one existing board to use driver model serial
+- (if no boards remain that don't use driver model) remove the old code
+
+This may be a good time to move your board to use device tree also. Mostly
+this involves these steps:
+
+- define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
+- add your device tree files to arch/<arch>/dts
+- update the Makefile there
+- Add stdout-path to your /chosen device tree node if it is not already there
+- build and get u-boot-dtb.bin so you can test it
+- Your drivers can now use device tree
+- For device tree in SPL, define CONFIG_SPL_OF_CONTROL