57 lines
2.1 KiB
ReStructuredText
57 lines
2.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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How to port an I2C driver to driver model
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=========================================
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Over half of the I2C drivers have been converted as at November 2016. These
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ones remain:
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* adi_i2c
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* davinci_i2c
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* fti2c010
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* ihs_i2c
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* kona_i2c
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* lpc32xx_i2c
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* pca9564_i2c
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* ppc4xx_i2c
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* rcar_i2c
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* sh_i2c
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* soft_i2c
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* zynq_i2c
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The deadline for this work is the end of June 2017. If no one steps
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forward to convert these, at some point there may come a patch to remove them!
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Here is a suggested approach for converting your I2C driver over to driver
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model. Please feel free to update this file with your ideas and suggestions.
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- #ifdef out all your own I2C driver code (#if !CONFIG_IS_ENABLED(DM_I2C))
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- Define CONFIG_DM_I2C for your board, vendor or architecture
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- If the board does not already use driver model, you need CONFIG_DM also
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- Your board should then build, but will not work fully since there will be
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no I2C driver
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- Add the U_BOOT_DRIVER piece at the end (e.g. copy tegra_i2c.c for example)
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- Add a private struct for the driver data - avoid using static variables
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- Implement each of the driver methods, perhaps by calling your old methods
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- You may need to adjust the function parameters so that the old and new
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implementations can share most of the existing code
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- If you convert all existing users of the driver, remove the pre-driver-model
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code
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In terms of patches a conversion series typically has these patches:
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- clean up / prepare the driver for conversion
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- add driver model code
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- convert at least one existing board to use driver model serial
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- (if no boards remain that don't use driver model) remove the old code
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This may be a good time to move your board to use device tree also. Mostly
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this involves these steps:
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- define CONFIG_OF_CONTROL and CONFIG_OF_SEPARATE
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- add your device tree files to arch/<arch>/dts
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- update the Makefile there
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- Add stdout-path to your /chosen device tree node if it is not already there
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- build and get u-boot-dtb.bin so you can test it
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- Your drivers can now use device tree
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- For device tree in SPL, define CONFIG_SPL_OF_CONTROL
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