At Sat, 3 Jan 2015 09:27:52 +0100, Takashi Iwai wrote:

A BUG_ON() call in dce3_2_afmt_write_sad_regs() is triggered when a HDMI monitor without SAD is plugged as the case sad_count = 0 is overlooked in the code:

kernel BUG at ../drivers/gpu/drm/radeon/dce3_1_afmt.c:110! invalid opcode: 0000 [#1] PREEMPT SMP CPU: 2 PID: 967 Comm: Xorg Tainted: PO 3.16.7-7-desktop #1 Hardware name: System manufacturer System Product Name/M4A77T, BIOS 2401 05/18/2011 task: ffff8800cea86350 ti: ffff8800c1880000 task.ti: ffff8800c1880000 RIP: 0010:[<ffffffffa0126c50>] dce3_1_hdmi_setmode+0x570/0x5a0 [radeon] Call Trace: [<ffffffffa00a6936>] drm_crtc_helper_set_mode+0x346/0x520 [drm_kms_helper] [<ffffffffa00a7678>] drm_crtc_helper_set_config+0x8a8/0xad0 [drm_kms_helper] [<ffffffffa00ede3f>] radeon_crtc_set_config+0x3f/0x110 [radeon] [<ffffffffa001edc1>] drm_mode_set_config_internal+0x61/0xe0 [drm] [<ffffffffa00a9a6b>] restore_fbdev_mode+0xab/0xd0 [drm_kms_helper] [<ffffffffa00a9aae>] drm_fb_helper_restore_fbdev_mode_unlocked+0x1e/0x30 [drm_kms_helper] [<ffffffffa00ab642>] drm_fb_helper_set_par+0x22/0x60 [drm_kms_helper] [<ffffffffa00ab5cb>] drm_fb_helper_hotplug_event+0x8b/0xe0 [drm_kms_helper] [<ffffffffa00ab65a>] drm_fb_helper_set_par+0x3a/0x60 [drm_kms_helper] [<ffffffff813818ce>] fb_set_var+0x15e/0x3b0 [<ffffffff81378d0b>] fbcon_blank+0x1cb/0x2b0 [<ffffffff813f2a31>] do_unblank_screen+0xa1/0x1b0 [<ffffffff813e8fd3>] complete_change_console+0x53/0xe0 [<ffffffff813e9fa9>] vt_ioctl+0xf49/0x10d0 [<ffffffff813ddfdc>] tty_ioctl+0x26c/0xb70 [<ffffffff811cad17>] do_vfs_ioctl+0x2e7/0x4c0 [<ffffffff811caf71>] SyS_ioctl+0x81/0xa0 [<ffffffff81622a2d>] system_call_fastpath+0x1a/0x1f [<00007f2fae8c6397>] 0x7f2fae8c6396

This patch fixes it by covering sad_count = 0 in the error check properly, too.

Bugzilla: https://bugzilla.opensuse.org/show_bug.cgi?id=911356 Cc: stable@vger.kernel.org Signed-off-by: Takashi Iwai tiwai@suse.de

---

IMO, BUG_ON() call itself is exaggerated there, but we may change it later independently from this fix.

drivers/gpu/drm/radeon/dce3_1_afmt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/radeon/dce3_1_afmt.c b/drivers/gpu/drm/radeon/dce3_1_afmt.c index 2fe8cfc966d9..bafdf92a5732 100644 --- a/drivers/gpu/drm/radeon/dce3_1_afmt.c +++ b/drivers/gpu/drm/radeon/dce3_1_afmt.c @@ -103,7 +103,7 @@ static void dce3_2_afmt_write_sad_regs(struct drm_encoder *encoder) }

sad_count = drm_edid_to_sad(radeon_connector->edid, &sads);

• if (sad_count < 0) {

• if (sad_count <= 0) { DRM_ERROR("Couldn't read SADs: %d\n", sad_count); return; }

Looking back at this fix again, this seems suboptimal, as it prints the error even in the correct case (sad_count = 0), and it doesn't set the register in the later code. I'm going to post a revised patch.

Takashi