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ARM: 9005/1: debug: Select flow control for all debug UARTs

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Instead of a flow control selection mechanism specifically for
8250, make this available for all debug UARTs. If the debug
UART supports waiting for CTS to be asserted, then this code
can be activated for terminals that need it.

We keep the defaults for EBSA110, Footbridge, Gemini and RPC
so that this still works as expected for these older platforms:
they assume that flow control shall be enabled for debug
prints.

I switch the location of the check for
ifdef CONFIG_DEBUG_UART_FLOW_CONTROL from the actual debug
UART drivers: the code would get compiled-out for 8250 and
Tegra unless their custom config (or passing -DFLOW_CONTROL
in the Tegra case) was not set. Instead this is conditional
at the three places where we print debug messages. The idea
is that debug UARTs can be implemented without this ifdef
boilerplate so they look cleaner, alas the ifdef has to be
somewhere.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Linus Walleij 2020-08-27 23:28:56 +01:00 committed by Russell King
parent 2c50a570e9
commit 4df24fef09
5 changed files with 19 additions and 10 deletions
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16
arch/arm/Kconfig.debug
View File

@ -1546,6 +1546,17 @@ config DEBUG_SIRFSOC_UART
bool
depends on ARCH_SIRF
config DEBUG_UART_FLOW_CONTROL
bool "Enable flow control (CTS) for the debug UART"
depends on DEBUG_LL
default y if ARCH_EBSA110 || DEBUG_FOOTBRIDGE_COM1 || DEBUG_GEMINI || ARCH_RPC
help
Some UART ports are connected to terminals that will use modem
control signals to indicate whether they are ready to receive text.
In practice this means that the terminal is asserting the special
control signal CTS (Clear To Send). If your debug UART supports
this and your debug terminal will require it, enable this option.
config DEBUG_LL_INCLUDE
string
default "debug/sa1100.S" if DEBUG_SA1100
@ -1893,11 +1904,6 @@ config DEBUG_UART_8250_PALMCHIP
except for having a different register layout. Say Y here if
the debug UART is of this type.
config DEBUG_UART_8250_FLOW_CONTROL
bool "Enable flow control for 8250 UART"
depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
default y if ARCH_EBSA110 || DEBUG_FOOTBRIDGE_COM1 || DEBUG_GEMINI || ARCH_RPC
config DEBUG_UNCOMPRESS
bool "Enable decompressor debugging via DEBUG_LL output"
depends on ARCH_MULTIPLATFORM || PLAT_SAMSUNG || ARM_SINGLE_ARMV7M

2
arch/arm/boot/compressed/debug.S
View File

@ -8,7 +8,9 @@
ENTRY(putc)
addruart r1, r2, r3
#ifdef CONFIG_DEBUG_UART_FLOW_CONTROL
waituartcts r3, r1
#endif
waituarttxrdy r3, r1
senduart r0, r1
busyuart r3, r1

2
arch/arm/include/debug/8250.S
View File

@ -49,9 +49,7 @@
.endm
.macro waituartcts,rd,rx
#ifdef CONFIG_DEBUG_UART_8250_FLOW_CONTROL
1001: load \rd, [\rx, #UART_MSR << UART_SHIFT]
tst \rd, #UART_MSR_CTS
beq 1001b
#endif
.endm

2
arch/arm/include/debug/tegra.S
View File

@ -179,14 +179,12 @@
.endm
.macro waituartcts, rd, rx
#ifdef FLOW_CONTROL
cmp \rx, #0
beq 1002f
1001: ldrb \rd, [\rx, #UART_MSR << UART_SHIFT]
tst \rd, #UART_MSR_CTS
beq 1001b
1002:
#endif
.endm
.macro waituarttxrdy,rd,rx

7
arch/arm/kernel/debug.S
View File

@ -89,12 +89,17 @@ ENTRY(printascii)
2: teq r1, #'\n'
bne 3f
mov r1, #'\r'
#ifdef CONFIG_DEBUG_UART_FLOW_CONTROL
waituartcts r2, r3
#endif
waituarttxrdy r2, r3
senduart r1, r3
busyuart r2, r3
mov r1, #'\n'
3: waituartcts r2, r3
3:
#ifdef CONFIG_DEBUG_UART_FLOW_CONTROL
waituartcts r2, r3
#endif
waituarttxrdy r2, r3
senduart r1, r3
busyuart r2, r3