[PATCH 0/8] soc: samsung: Add USIv2 driver

Sam Protsenko
2021-11-27T22:36:20Z

USIv2 IP-core provides selectable serial protocol (UART, SPI or
High-Speed I2C); only one can be chosen at a time. This series
implements USIv2 driver, which allows one to select particular USI
function in device tree, and also performs USI block initialization.

With that driver implemented, it's not needed to do USI initialization
in protocol drivers anymore, so that code is removed from the serial
driver.

Because USI driver is tristate (can be built as a module), serial driver
was reworked so it's possible to use its console part as a module too.
This way we can load serial driver module from user space and still have
serial console functional.

Make it impossible to build UART/SPI/I2C driver as a built-in when USIv2
driver built as a module: USIv2 configuration must be always done before
tinkering with particular protocol it implements.

Design features:
- "reg" property contains USI registers start address (0xc0 offset);
it's used in the driver to access USI_CON and USI_OPTION registers.
This way all USI initialization (reset, HWACG, etc) can be done in
USIv2 driver separately, rather than duplicating that code over
UART/SPI/I2C drivers
- System Register (system controller node) and its SW_CONF register
offset are provided in "samsung,sysreg" property; it's used to
select USI function (protocol to be used)
- USI function is specified in "samsung,mode" property; integer value
is used to simplify parsing
- there is "samsung,clkreq-on" bool property, which makes driver
disable HWACG control (needed for UART to work properly)
- PCLK and IPCLK clocks are both provided to USI node; apparently both
need to be enabled to access USI registers
- protocol nodes are embedded (as a child nodes) in USI node; it
allows correct init order, and reflects HW properly
- USIv2 driver is a tristate: can be also useful from Android GKI
requirements point of view
- driver functions are implemented with further development in mind:
we might want to add some SysFS interface later for example, or
provide some functions to serial drivers with EXPORT_SYMBOL(), etc

Sam Protsenko (8):
dt-bindings: soc: samsung: Add Exynos USIv2 bindings
dt-bindings: soc: samsung: Add Exynos USIv2 bindings doc
soc: samsung: Add USIv2 driver
tty: serial: samsung: Remove USI initialization
tty: serial: samsung: Enable console as module
tty: serial: Make SERIAL_SAMSUNG=y impossible when EXYNOS_USI_V2=m
i2c: Make I2C_EXYNOS5=y impossible when EXYNOS_USI_V2=m
spi: Make SPI_S3C64XX=y impossible when EXYNOS_USI_V2=m

.../bindings/soc/samsung/exynos-usi-v2.yaml | 124 +++++++++
drivers/i2c/busses/Kconfig | 1 +
drivers/soc/samsung/Kconfig | 14 +
drivers/soc/samsung/Makefile | 2 +
drivers/soc/samsung/exynos-usi-v2.c | 242 ++++++++++++++++++
drivers/spi/Kconfig | 1 +
drivers/tty/serial/Kconfig | 3 +-
drivers/tty/serial/samsung_tty.c | 57 ++---
.../dt-bindings/soc/samsung,exynos-usi-v2.h | 16 ++
include/linux/serial_s3c.h | 9 -
10 files changed, 425 insertions(+), 44 deletions(-)
create mode 100644 Documentation/devicetree/bindings/soc/samsung/exynos-usi-v2.yaml
create mode 100644 drivers/soc/samsung/exynos-usi-v2.c
create mode 100644 include/dt-bindings/soc/samsung,exynos-usi-v2.h

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2.30.2