Add support for debug communications channel based
hvc console for arm64 cpus.
Signed-off-by: NAbhimanyu Kapur <abhimany@codeaurora.org>
Signed-off-by: NTimur Tabi <timur@codeaurora.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The beat hvc driver is only used by celleb.
celleb has been dropped [1], so drop the drivers.

[1] http://patchwork.ozlabs.org/patch/451730/

CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: Jiri Slaby <jslaby@suse.cz>
CC: Valentin Rothberg <valentinrothberg@gmail.com>
CC: mpe@ellerman.id.au
CC: linuxppc-dev@lists.ozlabs.org
Signed-off-by: NDaniel Axtens <dja@axtens.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

The option allows you to remove TTY and compile without errors. This
saves space on systems that won't support TTY interfaces anyway.
bloat-o-meter output is below.

The bulk of this patch consists of Kconfig changes adding "depends on
TTY" to various serial devices and similar drivers that require the TTY
layer.  Ideally, these dependencies would occur on a common intermediate
symbol such as SERIO, but most drivers "select SERIO" rather than
"depends on SERIO", and "select" does not respect dependencies.

bloat-o-meter output comparing our previous minimal to new minimal by
removing TTY.  The list is filtered to not show removed entries with awk
'$3 != "-"' as the list was very long.

add/remove: 0/226 grow/shrink: 2/14 up/down: 6/-35356 (-35350)
function                                     old     new   delta
chr_dev_init                                 166     170      +4
allow_signal                                  80      82      +2
static.__warned                              143     142      -1
disallow_signal                               63      62      -1
__set_special_pids                            95      94      -1
unregister_console                           126     121      -5
start_kernel                                 546     541      -5
register_console                             593     588      -5
copy_from_user                                45      40      -5
sys_setsid                                   128     120      -8
sys_vhangup                                   32      19     -13
do_exit                                     1543    1526     -17
bitmap_zero                                   60      40     -20
arch_local_irq_save                          137     117     -20
release_task                                 674     652     -22
static.spin_unlock_irqrestore                308     260     -48
Signed-off-by: NJoe Millenbach <jmillenbach@gmail.com>
Reviewed-by: NJamey Sharp <jamey@minilop.net>
Reviewed-by: NJosh Triplett <josh@joshtriplett.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As discussed at the kernel summit this year, CONFIG_EXPERIMENTAL means
nothing, so let's get rid of it.

Cc: Kees Cook <keescook@chromium.org>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Also while at it, add some help text indicating why you shouldn't
enable that driver under normal circumstances
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

Introduce a new config option HVC_XEN_FRONTEND to enable/disable the
xenbus based pv console frontend.
Signed-off-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The PowerPC legacy iSeries platform is being removed, so this code is no
longer needed.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

This adds a udbg and an hvc console backend for supporting a console
using the OPAL console interfaces.

On OPAL v1 we have hvc0 mapped to whatever console the system was
configured for (network or hvsi serial port) via the service
processor.

On OPAL v2 we have hvcN mapped to the Nth console provided by OPAL
which generally corresponds to:

	hvc0 : network console (raw protocol)
	hvc1 : serial port S1 (hvsi)
	hvc2 : serial port S2 (hvsi)

Note: At this point, early debug console only works with OPAL v1
and shouldn't be enabled in a normal kernel.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

On pseries machines, consoles are provided by the hypervisor using
a low level get_chars/put_chars type interface. However, this is
really just a transport to the service processor which implements
them either as "raw" console (networked consoles, HMC, ...) or as
"hvsi" serial ports.

The later is a simple packet protocol on top of the raw character
interface that is supposed to convey additional "serial port" style
semantics. In practice however, all it does is provide a way to
read the CD line and set/clear our DTR line, that's it.

We currently implement the "raw" protocol as an hvc console backend
(/dev/hvcN) and the "hvsi" protocol using a separate tty driver
(/dev/hvsi0).

However this is quite impractical. The arbitrary difference between
the two type of devices has been a major source of user (and distro)
confusion. Additionally, there's an additional mini -hvsi implementation
in the pseries platform code for our low level debug console and early
boot kernel messages, which means code duplication, though that low
level variant is impractical as it's incapable of doing the initial
protocol negociation to establish the link to the FSP.

This essentially replaces the dedicated hvsi driver and the platform
udbg code completely by extending the existing hvc_vio backend used
in "raw" mode so that:

 - It now supports HVSI as well
 - We add support for hvc backend providing tiocm{get,set}
 - It also provides a udbg interface for early debug and boot console

This is overall less code, though this will only be obvious once we
remove the old "hvsi" driver, which is still available for now. When
the old driver is enabled, the new code still kicks in for the low
level udbg console, replacing the old mini implementation in the platform
code, it just doesn't provide the higher level "hvc" interface.

In addition to producing generally simler code, this has several benefits
over our current situation:

 - The user/distro only has to deal with /dev/hvcN for the hypervisor
console, avoiding all sort of confusion that has plagued us in the past

 - The tty, kernel and low level debug console all use the same code
base which supports the full protocol establishment process, thus the
console is now available much earlier than it used to be with the
old HVSI driver. The kernel console works much earlier and udbg is
available much earlier too. Hackers can enable a hard coded very-early
debug console as well that works with HVSI (previously that was only
supported for the "raw" mode).

I've tried to keep the same semantics as hvsi relative to how I react
to things like CD changes, with some subtle differences though:

 - I clear DTR on close if HUPCL is set

 - Current hvsi triggers a hangup if it detects a up->down transition
   on CD (you can still open a console with CD down). My new implementation
   triggers a hangup if the link to the FSP is severed, and severs it upon
   detecting a up->down transition on CD.
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

The Kconfig options for the drivers/tty/ files still were hanging around
in the "big" drivers/char/Kconfig file, so move them to the proper
location under drivers/tty and drivers/tty/hvc/
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>