linux/arch/powerpc
Paul Gortmaker 9deaa53ac7 serial: add irq handler for Freescale 16550 errata.
Sending a break on the SOC UARTs found in some MPC83xx/85xx/86xx
chips seems to cause a short lived IRQ storm (/proc/interrupts
typically shows somewhere between 300 and 1500 events).  Unfortunately
this renders SysRQ over the serial console completely inoperable.

The suggested workaround in the errata is to read the Rx register,
wait one character period, and then read the Rx register again.
We achieve this by tracking the old LSR value, and on the subsequent
interrupt event after a break, we don't read LSR, instead we just
read the RBR again and return immediately.

The "fsl,ns16550" is used in the compatible field of the serial
device to mark UARTs known to have this issue.

Thanks to Scott Wood for providing the errata data which led to
a much cleaner fix.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2011-12-09 19:14:13 -08:00
..
boot Merge remote-tracking branch 'agust/next' into merge 2011-11-08 14:53:55 +11:00
configs Merge remote-tracking branch 'agust/next' into merge 2011-11-08 14:53:55 +11:00
include/asm Merge branch 'kvm-updates/3.2' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2011-11-20 14:57:43 -08:00
kernel serial: add irq handler for Freescale 16550 errata. 2011-12-09 19:14:13 -08:00
kvm Merge branch 'kvm-updates/3.2' of git://git.kernel.org/pub/scm/virt/kvm/kvm 2011-11-20 14:57:43 -08:00
lib powerpc: Copy down exception vectors after feature fixups 2011-11-16 14:47:54 +11:00
math-emu powerpc/math_emu/efp: Look for errata handler when type mismatches 2011-10-06 23:36:47 -05:00
mm powerpc/numa: NUMA topology support for PowerNV 2011-11-08 14:51:46 +11:00
net net: filter: BPF 'JIT' compiler for PPC64 2011-07-21 12:38:32 -07:00
oprofile powerpc/oprofile: Handle events that raise an exception without overflowing 2011-05-26 13:38:57 +10:00
platforms powerpc/ps3: Fix SMP lockdep boot warning 2011-11-16 14:47:54 +11:00
sysdev Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-15 14:47:28 -02:00
xmon Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
Kconfig powerpc/4xx: Fix typos in kexec config dependencies 2011-11-16 14:47:54 +11:00
Kconfig.debug powerpc/powernv: Support for OPAL console 2011-09-20 16:09:54 +10:00
Makefile powerpc: Remove buggy 9-year-old test for binutils < 2.12.1 2011-11-17 16:26:07 +11:00
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