From mboxrd@z Thu Jan 1 00:00:00 1970 From: mohammad.rasim96@gmail.com (MOHAMMAD RASIM) Date: Sat, 8 Sep 2018 19:48:39 +0300 Subject: Regression in drm: drm/fbdev doesn't initialize if set to triple buffer Message-ID: To: linus-amlogic@lists.infradead.org List-Id: linus-amlogic.lists.infradead.org Hi, I've an issue where the drm_meson driver doesn't work, it used to work in earlier 4.18 release and stopped working after about 4.18-rc3. My board is videostrong k2 pro (S905 SoC), I use the meson-gxbb-p201 device tree. on the latest 4.19 tree the board boots fine but the drm driver doesn't work, and spits the following error in dmesg [??? 2.489825] meson-drm d0100000.vpu: Queued 3 outputs on vpu [??? 2.494685] meson-drm d0100000.vpu: Failed to create d0100000.vpu debugfs directory [??? 2.502051] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [??? 2.508668] [drm] No driver support for vblank timestamp query. [??? 2.573756] meson-drm d0100000.vpu: bound c883a000.hdmi-tx (ops meson_dw_hdmi_ops) [??? 2.695917] meson-drm d0100000.vpu: [drm:drm_fb_helper_fbdev_setup] *ERROR* Failed to set fbdev configuration [??? 2.700310] meson-drm d0100000.vpu: master bind failed: -22 [??? 2.705747] meson-drm: probe of d0100000.vpu failed with error -22 Digging deeper into the problem revealed that the problem is related to the CONFIG_DRM_FBDEV_OVERALLOC option, If I set it to 100 or 200 it works fine and the drm driver works ( or by passing drm_kms_helper.drm_fbdev_overalloc=200 in the bootargs). The problem reappears when setting it to 300. Bisecting shows that the first bad commit that introduced this regression is this: 244007ecb6bb94fa4e9b9a969fa86f2ad86ec543 Another problem that I face and might be related is that the sometimes the boot get stuck on the following lines: [??? 2.501539] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013). [??? 2.508158] [drm] No driver support for vblank timestamp query. This problem is random and can't always reproduced, sometimes it takes a few reboots to get the board to boot pass those lines. Regards