Add basic Power Management Unit (PMU) driver for Exynos SoCs. For now
it's only capable of changing UART path in PMU, which is needed for
E850-96 board. The driver's structure resembles the exynos-pmu driver
from Linux kernel, and although it's very basic and slim at the moment,
it can be easily extended in future if the need arises.
UCLASS_NOP is used, as there are no benefits in using more elaborate
classes like UCLASS_MISC in this case. The DM_FLAG_PROBE_AFTER_BIND flag
is added in bind function, as the probe function must be always called
for this driver.
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
USIv2 IP-core is found on modern ARM64 Exynos SoCs (like Exynos850) and
provides selectable serial protocol (one of: UART, SPI, I2C). USIv2
registers usually reside in the same register map as a particular
underlying protocol it implements, but have some particular offset. E.g.
on Exynos850 the USI_UART has 0x13820000 base address, where UART
registers have 0x00..0x40 offsets, and USI registers have 0xc0..0xdc
offsets. Desired protocol can be chosen via SW_CONF register from System
Register block of the same domain as USI.
Before starting to use a particular protocol, USIv2 must be configured
properly:
1. Select protocol to be used via System Register
2. Clear "reset" flag in USI_CON
3. Configure HWACG behavior (e.g. for UART Rx the HWACG must be
disabled, so that the IP clock is not gated automatically); this is
done using USI_OPTION register
4. Keep both USI clocks (PCLK and IPCLK) running during USI registers
modification
This driver implements the above behavior. Of course, USIv2 driver
should be probed before UART/I2C/SPI drivers. It can be achieved by
embedding UART/I2C/SPI nodes inside of the USI node (in Device Tree);
driver then walks underlying nodes and instantiates those. Driver also
handles USI configuration on PM resume, as register contents can be lost
during CPU suspend.
This driver is designed with different USI versions in mind. So it
should be relatively easy to add new USI revisions to it later.
Driver's code was copied over from Linux kernel [1] and adapted
correspondingly for U-Boot API. UCLASS_MISC is used, and although no
misc operations are implemented, it makes it easier to probe the driver
this way (as compared to UCLASS_NOP) and keep the code compact.
[1] drivers/soc/samsung/exynos-usi.c
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
