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Andy Shevchenko 3379ddd8cb serial: 8250: Check UPF_IRQ_SHARED in advance 
commit 7febbcbc48 upstream.

The commit 54e53b2e80
  ("tty: serial: 8250: pass IRQ shared flag to UART ports")
nicely explained the problem:

---8<---8<---

On some systems IRQ lines between multiple UARTs might be shared. If so, the
irqflags have to be configured accordingly. The reason is: The 8250 port startup
code performs IRQ tests *before* the IRQ handler for that particular port is
registered. This is performed in serial8250_do_startup(). This function checks
whether IRQF_SHARED is configured and only then disables the IRQ line while
testing.

This test is performed upon each open() of the UART device. Imagine two UARTs
share the same IRQ line: On is already opened and the IRQ is active. When the
second UART is opened, the IRQ line has to be disabled while performing IRQ
tests. Otherwise an IRQ might handler might be invoked, but the IRQ itself
cannot be handled, because the corresponding handler isn't registered,
yet. That's because the 8250 code uses a chain-handler and invokes the
corresponding port's IRQ handling routines himself.

Unfortunately this IRQF_SHARED flag isn't configured for UARTs probed via device
tree even if the IRQs are shared. This way, the actual and shared IRQ line isn't
disabled while performing tests and the kernel correctly detects a spurious
IRQ. So, adding this flag to the DT probe solves the issue.

Note: The UPF_SHARE_IRQ flag is configured unconditionally. Therefore, the
IRQF_SHARED flag can be set unconditionally as well.

Example stack trace by performing `echo 1 > /dev/ttyS2` on a non-patched system:

|irq 85: nobody cared (try booting with the "irqpoll" option)
| [...]
|handlers:
|[<ffff0000080fc628>] irq_default_primary_handler threaded [<ffff00000855fbb8>] serial8250_interrupt
|Disabling IRQ #85

---8<---8<---

But unfortunately didn't fix the root cause. Let's try again here by moving
IRQ flag assignment from serial_link_irq_chain() to serial8250_do_startup().

This should fix the similar issue reported for 8250_pnp case.

Since this change we don't need to have custom solutions in 8250_aspeed_vuart
and 8250_of drivers, thus, drop them.

Fixes: 1c2f04937b ("serial: 8250: add IRQ trigger support")
Reported-by: Li RongQing <lirongqing@baidu.com>
Cc: Kurt Kanzenbach <kurt@linutronix.de>
Cc: Vikram Pandita <vikram.pandita@ti.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Acked-by: Kurt Kanzenbach <kurt@linutronix.de>
Link: https://lore.kernel.org/r/20200211135559.85960-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2020-02-28 17:23:35 +01:00
arch MIPS: ingenic: DTS: Fix watchdog nodes 2020-02-28 17:23:35 +01:00
block block, bfq: do not plug I/O for bfq_queues with no proc refs 2020-02-24 08:38:09 +01:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto crypto: essiv - fix AEAD capitalization and preposition use in help text 2020-02-24 08:38:32 +01:00
Documentation fbdev: fix numbering of fbcon options 2020-02-24 08:38:21 +01:00
drivers serial: 8250: Check UPF_IRQ_SHARED in advance 2020-02-28 17:23:35 +01:00
fs jbd2: fix ocfs2 corrupt when clearing block group bits 2020-02-28 17:23:34 +01:00
include USB: core: add endpoint-blacklist quirk 2020-02-28 17:23:31 +01:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:33:00 +00:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:36:39 -08:00
kernel tracing: Fix now invalid var_ref_vals assumption in trace action 2020-02-24 08:38:47 +01:00
lib lib/scatterlist.c: adjust indentation in __sg_alloc_table 2020-02-24 08:38:47 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm/mmu_gather: invalidate TLB correctly on batch allocation failure and flush 2020-02-11 04:37:14 -08:00
net sunrpc: Fix potential leaks in sunrpc_cache_unhash() 2020-02-24 08:38:40 +01:00
samples samples/bpf: Set -fno-stack-protector when building BPF programs 2020-02-24 08:38:15 +01:00
scripts bpf, btf: Always output invariant hit in pahole DWARF to BTF transform 2020-02-24 08:38:40 +01:00
security selinux: ensure we cleanup the internal AVC counters on error in avc_update() 2020-02-24 08:38:19 +01:00
sound ASoC: sun8i-codec: Fix setting DAI data format 2020-02-28 17:23:27 +01:00
tools tc-testing: add missing 'nsPlugin' to basic.json 2020-02-24 08:38:49 +01:00
usr gen_initramfs_list.sh: fix 'bad variable name' error 2020-01-04 00:00:48 +09:00
virt KVM: arm64: Treat emulated TVAL TimerValue as a signed 32-bit integer 2020-02-14 16:53:04 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap MAINTAINERS: update my email address 2020-01-11 14:33:39 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Linux 5.4-rc4 2019-10-29 04:43:29 -06:00
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: correct entries for ISDN/mISDN section 2020-02-11 04:36:38 -08:00
Makefile Linux 5.5.6 2020-02-24 08:38:51 +01:00
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.