From: Takashi Iwai <tiwai@suse.de>
To: dri-devel@lists.freedesktop.org
Cc: linux-kernel@vger.kernel.org,
"Ville Syrjälä" <ville.syrjala@linux.intel.com>
Subject: [PATCH] drm: Fix broken VT switch with video=1366x768 option
Date: Mon, 9 Jan 2017 15:56:14 +0100 [thread overview]
Message-ID: <20170109145614.29454-1-tiwai@suse.de> (raw)
I noticed that the VT switch doesn't work any longer with a Dell
laptop with 1366x768 eDP when the machine is connected with a DP
monitor. It behaves as if VT were switched, but the graphics remain
frozen. Actually the keyboard works, so I could switch back to VT7
again.
I tried to track down the problem, and encountered a long story until
we reach to this error:
- The machine is booted with video=1366x768 option (the distro
installer seems to add it as default).
- Recently, drm_helper_probe_single_connector_modes() deals with
cmdline modes, and it tries to create a new mode when no
matching mode is found.
- The drm_mode_create_from_cmdline_mode() creates a mode based on
either CVT of GFT according to the given cmdline mode; in our case,
it's 1366x768.
- Since both CVT and GFT can't express the width 1366 due to
alignment, the resultant mode becomes 1368x768, slightly larger than
the given size.
- Later on, the atomic commit is performed, and in
drm_atomic_check_only(), the size of each plane is checked.
- The size check of 1366x768 fails due to the above, and eventually
the whole VT switch fails.
Back in the history, we've had a manual fix-up of 1368x768 in various
places via c09dedb7a50e ("drm/edid: Add a workaround for 1366x768 HD
panel"), but they have been all in drm_edid.c at probing the modes
from EDID. For addressing the problem above, we need a similar hack
to the mode newly created from cmdline, manually adjusting the width
when the expected size is 1366 while we get 1368 instead.
Fixes: eaf99c749d43 ("drm: Perform cmdline mode parsing during...")
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/drm_modes.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index ac6a35212501..e6b19bc9021a 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1460,6 +1460,13 @@ drm_mode_create_from_cmdline_mode(struct drm_device *dev,
return NULL;
mode->type |= DRM_MODE_TYPE_USERDEF;
+ /* fix up 1368x768: GFT/CVT can't express 1366 width due to alignment */
+ if (cmd->xres == 1366 && mode->hdisplay == 1368) {
+ mode->hdisplay = 1366;
+ mode->hsync_start--;
+ mode->hsync_end--;
+ drm_mode_set_name(mode);
+ }
drm_mode_set_crtcinfo(mode, CRTC_INTERLACE_HALVE_V);
return mode;
}
--
2.11.0
next reply other threads:[~2017-01-09 14:56 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-09 14:56 Takashi Iwai [this message]
2017-01-10 11:28 ` [PATCH] drm: Fix broken VT switch with video=1366x768 option Ville Syrjälä
2017-01-10 11:36 ` Takashi Iwai
2017-01-10 12:41 ` Daniel Vetter
2017-01-10 12:45 ` Takashi Iwai
2017-01-11 17:05 ` Ville Syrjälä
2017-01-11 18:46 ` Takashi Iwai
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