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UART block is a part of USI (Universal Serial Interface) IP-core in
Samsung SoCs since Exynos9810 (e.g. in Exynos850). USI allows one to
enable one of three types of serial interface: UART, SPI or I2C. That's
possible because USI shares almost all internal circuits within each
protocol. USI also provides some additional registers so it's possible
to configure it.
One USI register called USI_OPTION has reset value of 0x0. Because of
this the clock gating behavior is controlled by hardware (HWACG =
Hardware Auto Clock Gating), which simply means the serial won't work
after reset as is. In order to make it work, USI_OPTION[2:1] bits must
be set to 0b01, so that HWACG is controlled manually (by software).
Bits meaning:
- CLKREQ_ON = 1: clock is continuously provided to IP
- CLKSTOP_ON = 0: drive IP_CLKREQ to High (needs to be set along with
CLKREQ_ON = 1)
USI is not present on older chips, like s3c2410, s3c2412, s3c2440,
s3c6400, s5pv210, exynos5433, exynos4210. So the new boolean field
'.has_usi' was added to struct s3c24xx_uart_info. USI registers will be
only actually accessed when '.has_usi' field is set to "1".
This feature is needed for further serial enablement on Exynos850, but
some other new Exynos chips (like Exynos9810) may benefit from this
feature as well.
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20210811114827.27322-5-semen.protsenko@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Apple SoCs are a distant descendant of Samsung designs and use yet
another variant of their UART style, with different interrupt handling.
In particular, this variant has the following differences with existing
ones:
* It includes a built-in interrupt controller with different registers,
using only a single platform IRQ
* Internal interrupt sources are treated as edge-triggered, even though
the IRQ output is level-triggered. This chiefly affects the TX IRQ
path: the driver can no longer rely on the TX buffer empty IRQ
immediately firing after TX is enabled, but instead must prime the
FIFO with data directly.
Signed-off-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Tested-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210304213902.83903-25-marcan@marcan.st
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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Correct the path to Samsung S3C24xx machine file, mentioned in
documentation.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200911143343.498-2-krzk@kernel.org
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Replace GPL license statements with SPDX GPL-2.0 and GPL-2.0+ license
identifiers.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
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This macro definitions are necessary to implement DMA transfers
is samsung serial driver.
Based on previous work of Sylwester Nawrocki and Lukasz Czerwinski.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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serial_s3c.h uses upf_t which is defined in serial_core.h but does not
include that itself meaning that users which include serial_s3c.h by
itself don't build.
Signed-off-by: Mark Brown <broonie@linaro.org>
[t.figa: Moved inclusion under #ifndef __ASSEMBLY__ to fix mach-exynos]
Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>
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The registers for the Samsung S3C serial port are currently defined in
the platform specific arch/arm/plat-samsung/include/plat/regs-serial.h
file, which is not visible to multiplatform capable drivers.
Unfortunately, it is not possible to move the file into a more local
place as we should normally try to, because the same registers
may be used in one of four places:
* In the driver itself
* In platform-independent ARM code for early debug output
* In platform_data definitions
* In the Samsung platform power management code
I have also found no way to logically split out a platform_data
file, other than possibly move everything into
include/linux/platform_data, which also felt wrong. The only
part of this file that makes sense to keep specific to the s3c24xx
platform are the virtual and physical addresses defined here,
which are needed in no other location.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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