[PATCH] drm/panel: sharp-ls043t1le01: make use of prepare_prev_first

[PATCH] drm/panel: sharp-ls043t1le01: make use of prepare_prev_first

[Dmitry Baryshkov]

The DSI link must be powered up to let panel driver to talk to the panel
during prepare() callback execution. Set the prepare_prev_first flag to
guarantee this.

Fixes: 9e15123eca79 ("drm/msm/dsi: Stop unconditionally powering up DSI hosts at modeset")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
 drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c b/drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c
index 36abfa2e65e9..dd1eaba23ad3 100644
--- a/drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c
+++ b/drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c
@@ -201,6 +201,7 @@ static int sharp_nt_panel_add(struct sharp_nt_panel *sharp_nt)
 
 	drm_panel_init(&sharp_nt->base, &sharp_nt->dsi->dev,
 		       &sharp_nt_panel_funcs, DRM_MODE_CONNECTOR_DSI);
+	sharp_nt->base.prepare_prev_first = true;
 
 	ret = drm_panel_of_backlight(&sharp_nt->base);
 	if (ret)

---
base-commit: 8e5a478b6d6a5bb0a3d52147862b15e4d826af19
change-id: 20260323-panel-fix-4e794508de92

Best regards,
-- 
With best wishes
Dmitry

Re: [PATCH] drm/panel: sharp-ls043t1le01: make use of prepare_prev_first

[Doug Anderson]

Hi,

On Sun, Mar 22, 2026 at 6:21 PM Dmitry Baryshkov
<dmitry.baryshkov@oss.qualcomm.com> wrote:
>
> The DSI link must be powered up to let panel driver to talk to the panel
> during prepare() callback execution. Set the prepare_prev_first flag to
> guarantee this.
>
> Fixes: 9e15123eca79 ("drm/msm/dsi: Stop unconditionally powering up DSI hosts at modeset")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---
>  drivers/gpu/drm/panel/panel-sharp-ls043t1le01.c | 1 +
>  1 file changed, 1 insertion(+)

Reviewed-by: Douglas Anderson <dianders@chromium.org>

Claude review: drm/panel: sharp-ls043t1le01: make use of prepare_prev_first

[Claude Code Review Bot]

Overall Series Review

Subject: drm/panel: sharp-ls043t1le01: make use of prepare_prev_first
Author: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patches: 2
Reviewed: 2026-03-25T08:09:53.961252

---

This is a straightforward, correct, single-patch fix. The Sharp LS043T1LE01 is a DSI panel whose `prepare()` callback sends DSI commands (exit sleep mode, set pixel format, set display on via `mipi_dsi_dcs_*` calls). After commit 9e15123eca79 stopped unconditionally powering up DSI hosts at modeset, the DSI link may not be ready when the panel's `prepare()` runs, causing those commands to fail. Setting `prepare_prev_first = true` ensures the DSI host is initialized before the panel's `prepare()` is called, which is the standard fix for this class of problem.

The patch is well-motivated, follows established patterns used by many other DSI panel drivers, and the placement after `drm_panel_init()` is correct and consistent with other drivers.

**Recommendation: Accept as-is.**

---
Generated by Claude Code Patch Reviewer

Claude review: drm/panel: sharp-ls043t1le01: make use of prepare_prev_first

[Claude Code Review Bot]

Patch Review

**Correctness:** The `prepare()` callback at line 102 calls `sharp_nt_panel_init()` which issues DSI commands (`mipi_dsi_dcs_exit_sleep_mode_multi`, `mipi_dsi_dcs_write_seq_multi`, etc.), and then `sharp_nt_panel_on()` which calls `mipi_dsi_dcs_set_display_on_multi`. All of these require an active DSI link. Setting `prepare_prev_first` is the correct fix.

**Placement:** The assignment:
```c
sharp_nt->base.prepare_prev_first = true;
```
is placed right after `drm_panel_init()` and before `drm_panel_of_backlight()`, which matches the pattern used across dozens of other panel drivers (e.g., `panel-boe-bf060y8m-aj0.c:353`, `panel-boe-tv101wum-nl6.c:1721`, etc.).

**Fixes tag:** Correctly references 9e15123eca79 which introduced the regression by stopping unconditional DSI host power-up.

**No issues found.** Clean, minimal, correct fix.

---
Generated by Claude Code Patch Reviewer