From mboxrd@z Thu Jan 1 00:00:00 1970 From: Claude Code Review Bot To: dri-devel-reviews@example.com Subject: Claude review: Re: [PATCH v2] drm: shmobile: Fix blank screen after resume when LCDC is stopped Date: Fri, 27 Feb 2026 12:34:03 +1000 Message-ID: In-Reply-To: References: X-Mailer: Claude Code Patch Reviewer Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Overall Series Review Subject: Re: [PATCH v2] drm: shmobile: Fix blank screen after resume when L= CDC is stopped Author: Geert Uytterhoeven Patches: 3 Reviewed: 2026-02-27T12:34:03.437511 --- This mbox contains two versions of the same patch: v1 (`[PATCH]`) and v2 (`= [PATCH v2]`), where v2 supersedes v1. The fix addresses a real issue with t= he SH Mobile LCDC driver where the display start address (SA) is written vi= a the mirror register mechanism during resume, but the controller is stoppe= d (DO=3D0) so no Frame End interrupt fires to transfer the mirrored value i= nto the active register set. The analysis is sound and well-supported by the hardware architecture: - `lcdc_write_mirror()` writes to `reg + LCDC_MIRROR_OFFSET (0x2000)`, the = standby/mirror register - The MRS toggle requests the hardware to switch sets on the next Frame End - When DO=3D0, no frames are processed, so the switch never occurs - `lcdc_write()` writes directly to both Set A (`reg`) and Set B (`reg + LC= DC_SIDE_B_OFFSET (0x1000)`) for banked registers (LDSA1R and LDSA2R are bot= h banked per `lcdc_is_banked()`) The commit ordering confirms the scenario: since shmobile uses the default = `drm_atomic_helper_commit_tail()` (no custom `commit_tail` override), the s= equence during a modeset/resume is: 1. `drm_atomic_helper_commit_planes()` =E2=86=92 `shmob_drm_primary_plane_s= etup()` (DO=3D0 at this point) 2. `drm_atomic_helper_commit_modeset_enables()` =E2=86=92 `shmob_drm_crtc_a= tomic_enable()` =E2=86=92 `shmob_drm_crtc_start_stop(scrtc, true)` (sets DO= =3D1) So when the plane setup runs, the LCDC is indeed stopped and the mirror mec= hanism cannot work. --- Generated by Claude Code Patch Reviewer