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This patch was triggered by a remark from Russell that
introducing a call to the waituart (needed to fix debug prints
on the Qualcomm platforms) was dangerous because in some cases
this will involve waiting for a modem CTS (clear to send)
signal, and debug messages would maybe not work on platforms
with no modem connected to the UART port: they will just
hang waiting for the modem to assert CTS and this might never
happen.
Looking through all UART debug drivers implementing the waituart
macro I discovered that all users except two actually use this
macro to check if the UART is ready for TX, let's call this
TXRDY.
Only two debug UART drivers actually check for CTS:
- arch/arm/include/debug/8250.S
- arch/arm/include/debug/tegra.S
The former is very significant since the 8250 is possibly
the most common UART on the planet.
We have the following problem: the semantics of waituart are
ambiguous making it dangerous to introduce the macro to debug
code fixing debug prints for Qualcomm. To start to pry this
problem apart, this patch does the following:
- Convert all debug UART drivers to define two macros:
- waituartcts with the clear semantic to wait for CTS
to be asserted
- waituarttxrdy with the clear semantic to wait for the TX
capability of the UART to be ready
- When doing this take care to assign the right function to
each drivers macro, so they now do exactly the above.
- Update the three sites in the kernel invoking the waituart
macro to call waituartcts/waituarttxrdy in sequence, so that
the functional impact on the kernel should be zero.
After this we can start to change the code sites using this
code to do the right thing.
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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Based on 2 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license version 2 as
published by the free software foundation #
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 4122 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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AT91 still uses an offset (0x0100 0000) from the physical address to map
the debug UART. This is unfortunate as for some platforms (sama5d3 and
earlier), it ends up in the PCI zone and PCI is enabled in multi_v7.
Switch to DEBUG_UART_VIRT to solve that.
Tested on sama5d3 and 9g20.
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
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In an invalid randconfig build (fixed by another patch),
I ran across this warning:
arch/arm/include/debug/at91.S:18:0: error: "CONFIG_DEBUG_UART_VIRT" redefined [-Werror]
#define CONFIG_DEBUG_UART_VIRT AT91_IO_P2V(CONFIG_DEBUG_UART_PHYS)
As Russell pointed out, we should never #define a macro starting
with CONFIG_ in a source file, as that is rather confusing.
This renames the macro to avoid the symbol clash.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Russell King <linux@arm.linux.org.uk>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
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Instead of having to add a new configuration option each time support for
new SoC is added, use CONFIG_DEBUG_UART_PHYS. For now,
CONFIG_DEBUG_UART_VIRT is automatically computed.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
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Add Kconfig entries, header file changes and addition to the documentation.
The early debug infrastructure is also added for easy development.
Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
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Linux may be used without MMU on atmel SoCs, fix debug in this configuration.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
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Move debug-macro.S from include/mach/ to include/debug where all other common
debug macros are.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
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