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Manasi Navare 40ee6fbef7 drm: Add a new connector atomic property for link status
At the time userspace does setcrtc, we've already promised the mode
would work. The promise is based on the theoretical capabilities of
the link, but it's possible we can't reach this in practice. The DP
spec describes how the link should be reduced, but we can't reduce
the link below the requirements of the mode. Black screen follows.

One idea would be to have setcrtc return a failure. However, it
already should not fail as the atomic checks have passed. It would
also conflict with the idea of making setcrtc asynchronous in the
future, returning before the actual mode setting and link training.

Another idea is to train the link "upfront" at hotplug time, before
pruning the mode list, so that we can do the pruning based on
practical not theoretical capabilities. However, the changes for link
training are pretty drastic, all for the sake of error handling and
DP compliance, when the most common happy day scenario is the current
approach of link training at mode setting time, using the optimal
parameters for the mode. It is also not certain all hardware could do
this without the pipe on; not even all our hardware can do this. Some
of this can be solved, but not trivially.

Both of the above ideas also fail to address link degradation *during*
operation.

The solution is to add a new "link-status" connector property in order
to address link training failure in a way that:
a) changes the current happy day scenario as little as possible, to
avoid regressions, b) can be implemented the same way by all drm
drivers, c) is still opt-in for the drivers and userspace, and opting
out doesn't regress the user experience, d) doesn't prevent drivers
from implementing better or alternate approaches, possibly without
userspace involvement. And, of course, handles all the issues presented.
In the usual happy day scenario, this is always "good". If something
fails during or after a mode set, the kernel driver can set the link
status to "bad" and issue a hotplug uevent for userspace to have it
re-check the valid modes through GET_CONNECTOR IOCTL, and try modeset
again. If the theoretical capabilities of the link can't be reached,
the mode list is trimmed based on that.

v7 by Jani:
* Rebase, simplify set property while at it, checkpatch fix
v6:
* Fix a typo in kernel doc (Sean Paul)
v5:
* Clarify doc for silent rejection of atomic properties by driver (Daniel Vetter)
v4:
* Add comments in kernel-doc format (Daniel Vetter)
* Update the kernel-doc for link-status (Sean Paul)
v3:
* Fixed a build error (Jani Saarinen)
v2:
* Removed connector->link_status (Daniel Vetter)
* Set connector->state->link_status in drm_mode_connector_set_link_status_property
(Daniel Vetter)
* Set the connector_changed flag to true if connector->state->link_status changed.
* Reset link_status to GOOD in update_output_state (Daniel Vetter)
* Never allow userspace to set link status from Good To Bad (Daniel Vetter)

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Tony Cheng <tony.cheng@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Eric Anholt <eric@anholt.net> (for the -modesetting patch)
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/0182487051aa9f1594820e35a4853de2f8747b4e.1481883920.git.jani.nikula@intel.com
2017-02-27 10:24:25 +01:00
arch Linux 4.10-rc8 2017-02-23 12:10:12 +10:00
block block: don't try Write Same from __blkdev_issue_zeroout 2017-02-06 09:34:46 -07:00
certs certs: Add a secondary system keyring that can be added to dynamically 2016-04-11 22:48:09 +01:00
crypto crypto: algif_aead - Fix kernel panic on list_del 2017-02-03 17:45:48 +08:00
Documentation Merge airlied/drm-next into drm-misc-next 2017-02-26 21:34:42 +01:00
drivers drm: Add a new connector atomic property for link status 2017-02-27 10:24:25 +01:00
firmware WHENCE: use https://linuxtv.org for LinuxTV URLs 2015-12-04 10:35:11 -02:00
fs Merge branch 'for-linus-4.10' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2017-02-11 09:15:58 -08:00
include drm: Add a new connector atomic property for link status 2017-02-27 10:24:25 +01:00
init kbuild: modversions: add infrastructure for emitting relative CRCs 2017-02-03 08:28:25 -08:00
ipc ipc/sem.c: fix incorrect sem_lock pairing 2017-01-10 18:31:55 -08:00
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-02-11 10:24:16 -08:00
lib lib/Kconfig: make PRIME_NUMBERS not user selectable. 2017-02-24 12:11:21 +10:00
mm mm/slub.c: fix random_seq offset destruction 2017-02-08 15:41:43 -08:00
net l2tp: do not use udp_ioctl() 2017-02-10 15:57:34 -05:00
samples bpf: fix samples xdp_tx_iptunnel and tc_l2_redirect with fake KBUILD_MODNAME 2017-01-20 12:04:07 -05:00
scripts kbuild: modversions: add infrastructure for emitting relative CRCs 2017-02-03 08:28:25 -08:00
security selinux: fix off-by-one in setprocattr 2017-02-08 19:09:53 +11:00
sound Linux 4.10-rc8 2017-02-23 12:10:12 +10:00
tools Linux 4.10-rc8 2017-02-23 12:10:12 +10:00
usr kbuild: initramfs cleanup, set target from Kconfig 2017-01-05 09:40:16 -08:00
virt KVM/ARM updates for 4.10-rc4 2017-01-17 15:04:59 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2016-08-02 16:48:52 -04:00
.mailmap mailmap: add codeaurora.org names for nameless email commits 2017-01-10 18:31:55 -08:00
COPYING
CREDITS CREDITS: Remove outdated address information 2016-12-21 15:21:29 -08:00
Kbuild scripts/gdb: provide linux constants 2016-05-23 17:04:14 -07:00
Kconfig
MAINTAINERS Linux 4.10-rc8 2017-02-23 12:10:12 +10:00
Makefile Linux 4.10-rc8 2017-02-12 13:03:20 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.