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[0/5] video: add support for MIPI DBI interface

Message ID 20240614-mipi_dbi-v1-0-946eb82f8533@jookia.org
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Series video: add support for MIPI DBI interface | expand

Message

John Watts June 14, 2024, 12:18 p.m. UTC 
Many simple RGB panels use a MIPI DBI interface over SPI, so this patch
adds support for this interface using an API compatible with Linux.

The MIPI DBI interface works similar to SPI using 8-bit words in the
format of: COMMAND DATA1 DATA2 ...
However the interface has two variations on this.

The first variation is implemented by this patch series: Using 9-bit
words, with the first bit signalling whether the word is a COMMAND or
DATA.

The second variation is not implemented by this series: A GPIO is held
at a value during an 8-bit word to indicate if it's a COMMAND or WORD.
Adding support for this wouldn't be too hard, but I don't have any
hardware to test it on.

Linux seems to not implement the specification correctly: It sets CS
inactive between words instead of keeping it active for the entire
transaction. I'm copying this behaviour to keep compatibility in porting
panels across from the kernel.

Signed-off-by: John Watts <contact@jookia.org>
---
John Watts (5):
      spi: Return old wordlen in spit_set_wordlen
      spi: Limit spi_set_wordlen to SPI_DEFAULT_WORDLEN
      spi: Implement spi_set_wordlen for driver model
      spi: softspi: Support setting wordlen
      video: add support for MIPI DBI interface

 drivers/spi/soft_spi.c   |  7 +++++
 drivers/spi/spi-uclass.c | 29 +++++++++++++++++++
 drivers/spi/spi.c        |  6 ++--
 drivers/video/Kconfig    |  6 ++++
 drivers/video/Makefile   |  1 +
 drivers/video/mipi_dbi.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++
 include/mipi_dbi.h       | 73 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/spi.h            |  2 +-
 8 files changed, 191 insertions(+), 3 deletions(-)
---
base-commit: c0ea27bccfb7d2d37fd36806ac2a2f7389099420
change-id: 20240601-mipi_dbi-aeda98f2f9d5

Best regards,