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>
Based on 1 normalized pattern(s):
licensed under gplv2 or later
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 118 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jilayne Lovejoy <opensource@jilayne.com>
Reviewed-by: Steve Winslow <swinslow@gmail.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190519154040.961286471@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
this patch adds UART0 and UART1 as LLUART port, as the new Atlas7
registers layout are different, it also refines some names of old
hard-coded MARCOs and uses CONFIG_DEBUG_UART_PHYS/DEBUG_UART_VIRT
to define different base addresses for multiple ports.
Signed-off-by: Guo Zeng <Guo.Zeng@csr.com>
Signed-off-by: Zhiwu Song <Zhiwu.Song@csr.com>
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Marco will not be supported any more. it has been replaced by CSR
Atlas7.
Signed-off-by: Barry Song <Baohua.Song@csr.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
The new style ll_debug implementation for multiplatform requires the
platform glue to be in include/debug, so let's move it there to
separate the debugging logic from the platform code.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Barry Song <Baohua.Song@csr.com>
2013-03-25 12:29:40 +01:00
Renamed from arch/arm/mach-prima2/include/mach/debug-macro.S (Browse further)
