Hi,
recently I noticed that VT console doesn't work any longer when I dock a Dell E7270 laptop with a DP monitor. The bug detail is like this:
At first, I boot the laptop without dock. I can switch between X and VT via ctrl-alt-F1, so far. Then I dock it to a docking station connected with a DP monitor. Now, when I switch to VT, it behaves as if frozen, the X graphics screen remains. But actually it's only graphics and the keyboard input is processed in VT. I can go back to X via alt-F7 again. The situation remains until I undock and I kill X once.
After looking more deeply at drm debug log, I found out that it's caused by the drm atomic check. Essentially, it's because eDP has the lower resolution (1366x768) than DP (1920x1080). Since booting with eDP, the frame buffer size is 1366x768. Then it hits the following check in drm_atomic_plane_check():
fb_width = state->fb->width << 16; fb_height = state->fb->height << 16;
/* Make sure source coordinates are inside the fb. */ if (state->src_w > fb_width || state->src_x > fb_width - state->src_w || state->src_h > fb_height || state->src_y > fb_height - state->src_h) { DRM_DEBUG_ATOMIC("Invalid source coordinates " "%u.%06ux%u.%06u+%u.%06u+%u.%06u\n", state->src_w >> 16, ((state->src_w & 0xffff) * 15625) >> 10, state->src_h >> 16, ((state->src_h & 0xffff) * 15625) >> 10, state->src_x >> 16, ((state->src_x & 0xffff) * 15625) >> 10, state->src_y >> 16, ((state->src_y & 0xffff) * 15625) >> 10); return -ENOSPC; }
Actually after commenting out "return -ENOSPC", VT switch works fine.
But the code above made me wonder what's the requirement here. IIRC, the VT always worked on a display with a higher resolution even if the frame buffer is smaller. Only a part of display was used, but it was OK, far better than the frozen graphics :)
Can we simply drop this check, or may we add a flag to skip it for VT switching? Or any better idea?
thanks,
Takashi