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Helmut Grohne a44c859323 tty: xilinx_uartps: Really fix id assignment 
commit 22a82fa7d6 upstream.

The problems started with the revert (18cc7ac8a2). The
cdns_uart_console.index is statically assigned -1. When the port is
registered, Linux assigns consecutive numbers to it. It turned out that
when using ttyPS1 as console, the index is not updated as we are reusing
the same cdns_uart_console instance for multiple ports. When registering
ttyPS0, it gets updated from -1 to 0, but when registering ttyPS1, it
already is 0 and not updated.

That led to 2ae11c46d5. It assigns the index prior to registering
the uart_driver once. Unfortunately, that ended up breaking the
situation where the probe order does not match the id order. When using
the same device tree for both uboot and linux, it is important that the
serial0 alias points to the console. So some boards reverse those
aliases. This was reported by Jan Kiszka. The proposed fix was reverting
the index assignment and going back to the previous iteration.

However such a reversed assignement (serial0 -> uart1, serial1 -> uart0)
was already partially broken by the revert (18cc7ac8a2). While the
ttyPS device works, the kmsg connection is already broken and kernel
messages go missing. Reverting the id assignment does not fix this.

>From the xilinx_uartps driver pov (after reverting the refactoring
commits), there can be only one console. This manifests in static
variables console_pprt and cdns_uart_console. These variables are not
properly linked and can go out of sync. The cdns_uart_console.index is
important for uart_add_one_port. We call that function for each port -
one of which hopefully is the console. If it isn't, the CON_ENABLED flag
is not set and console_port is cleared. The next cdns_uart_probe call
then tries to register the next port using that same cdns_uart_console.

It is important that console_port and cdns_uart_console (and its index
in particular) stay in sync. The index assignment implemented by
Shubhrajyoti Datta is correct in principle. It just may have to happen a
second time if the first cdns_uart_probe call didn't encounter the
console device. And we shouldn't change the index once the console uart
is registered.

Reported-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
Reported-by: Jan Kiszka <jan.kiszka@web.de>
Link: https://lore.kernel.org/linux-serial/f4092727-d8f5-5f91-2c9f-76643aace993@siemens.com/
Fixes: 18cc7ac8a2 ("Revert "serial: uartps: Register own uart console and driver structures"")
Fixes: 2ae11c46d5 ("tty: xilinx_uartps: Fix missing id assignment to the console")
Fixes: 76ed2e1057 ("Revert "tty: xilinx_uartps: Fix missing id assignment to the console"")
Signed-off-by: Helmut Grohne <helmut.grohne@intenta.de>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200713073227.GA3805@laureti-dev
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2020-07-29 10:18:41 +02:00
Documentation doc: dt: bindings: usb: dwc3: Update entries for disabling SS instances in park mode 2020-07-22 09:32:59 +02:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch RISC-V: Upgrade smp_mb__after_spinlock() to iorw,iorw 2020-07-29 10:18:40 +02:00
block block: fix get_max_segment_size() overflow on 32bit arch 2020-07-22 09:33:17 +02:00
certs PKCS#7: Refactor verify_pkcs7_signature() 2019-08-05 18:40:18 -04:00
crypto keys: asymmetric: fix error return code in software_key_query() 2020-07-22 09:33:04 +02:00
drivers tty: xilinx_uartps: Really fix id assignment 2020-07-29 10:18:41 +02:00
fs Revert "cifs: Fix the target file was deleted when rename failed." 2020-07-29 10:18:41 +02:00
include asm-generic/mmiowb: Allow mmiowb_set_pending() when preemptible() 2020-07-29 10:18:40 +02:00
init x86: Fix early boot crash on gcc-10, third try 2020-05-20 08:20:34 +02:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel uprobes: Change handle_swbp() to send SIGTRAP with si_code=SI_KERNEL, to fix GDB regression 2020-07-29 10:18:29 +02:00
lib test_objagg: Fix potential memory leak in error handling 2020-06-30 15:37:04 -04:00
mm mm, compaction: make capture control handling safe wrt interrupts 2020-07-09 09:37:57 +02:00
net ipvs: fix the connection sync failed in some cases 2020-07-29 10:18:34 +02:00
samples samples/vfs: avoid warning in statx override 2020-07-09 09:37:54 +02:00
scripts scripts/gdb: fix lx-symbols 'gdb.error' while loading modules 2020-07-29 10:18:35 +02:00
security apparmor: ensure that dfa state tables have entries 2020-07-22 09:33:05 +02:00
sound ALSA: hda/realtek - fixup for yet another Intel reference board 2020-07-29 10:18:39 +02:00
tools perf stat: Zero all the 'ena' and 'run' array slot stats for interval mode 2020-07-22 09:33:05 +02:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: arm64: Save the host's PtrAuth keys in non-preemptible context 2020-06-17 16:40:38 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Update drm/i915 bug filing URL 2020-02-28 17:22:19 +01:00
Makefile Linux 5.4.53 2020-07-22 09:33:18 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.