[PATCH AUTOSEL 6.19-6.18] drm/panel-edp: Add AUO B140QAX01.H panel

[Sasha Levin <sashal@kernel.org>]

From: Val Packett <val@packett.cool>

[ Upstream commit bcd752c706c357229185a330ab450b86236d9031 ]

A 14-inch 2560x1600 60Hz matte touch panel, found on a Dell Latitude 7455
laptop (second-source with BOE NE14QDM), according to online sources it's
also found on the Latitude 7440 and some ASUS models.

Raw EDID dump:

00 ff ff ff ff ff ff 00 06 af a4 0b 00 00 00 00
00 20 01 04 a5 1e 13 78 03 ad f5 a8 54 47 9c 24
0e 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
01 01 01 01 01 01 f0 68 00 a0 a0 40 2e 60 30 20
35 00 2d bc 10 00 00 1a f3 53 00 a0 a0 40 2e 60
30 20 35 00 2d bc 10 00 00 1a 00 00 00 fe 00 36
39 52 31 57 80 42 31 34 30 51 41 58 00 00 00 00
00 02 41 21 a8 00 01 00 00 1a 41 0a 20 20 00 a1

Don't have datasheet access, but the same timing as for other panels from
the same manufacturer works fine.

Signed-off-by: Val Packett <val@packett.cool>
[dianders: Moved to the right location in the table]
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://patch.msgid.link/20251206173739.2222940-1-val@packett.cool
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

This is the same author (Val Packett), same laptop (Dell Latitude 7455),
and a second-source panel for it. Let me verify this is a pure one-line
panel ID addition and check the exact diff once more.

The commit message itself says this AUO B140QAX01.H is a "second-source
with BOE NE14QDM" -- meaning the Dell Latitude 7455 can come with either
panel, and the BOE variant was already added.

## Analysis

### 1. COMMIT MESSAGE ANALYSIS

The commit adds a new eDP panel entry for the **AUO B140QAX01.H** panel.
Key details:
- 14-inch 2560x1600 60Hz matte touch panel
- Found on real shipping hardware: **Dell Latitude 7455**, Dell Latitude
  7440, and some ASUS models
- It's a second-source panel alongside the already-listed BOE NE14QDM
- Author has the actual hardware and tested it
- Reviewed by Douglas Anderson (the `panel-edp` subsystem maintainer)

### 2. CODE CHANGE ANALYSIS

The change is a **single line addition** to the `edp_panels[]` table:

```c
EDP_PANEL_ENTRY('A', 'U', 'O', 0x0ba4, &delay_200_500_e50,
"B140QAX01.H"),
```

This uses:
- The existing `EDP_PANEL_ENTRY` macro
- An existing delay structure `delay_200_500_e50` (used by nearly all
  other AUO panels in the table)
- Placed in the correct sorted position (after 0x04a4, before 0x105c)

There is **zero new logic, zero new delay structures, zero new
functions** -- it is purely a data table entry.

### 3. CLASSIFICATION: Device ID / Hardware Enablement

This falls squarely under the **"NEW DEVICE IDs"** exception category
for stable backports:
- Adding a panel ID to an existing driver (`panel-edp.c`)
- The driver infrastructure already exists in all stable trees where
  `panel-edp.c` exists
- The `delay_200_500_e50` delay structure already exists
- The `EDP_PANEL_ENTRY` macro already exists

### 4. USER IMPACT: What happens without this entry?

Looking at the code in `generic_edp_panel_probe()` (lines 805-825):

```809:825:drivers/gpu/drm/panel/panel-edp.c
        /*
  - We're using non-optimized timings and want it really obvious that
  - someone needs to add an entry to the table, so we'll do a WARN_ON
  - splat.
         */
        if (WARN_ON(!panel->detected_panel)) {
                dev_warn(dev,
                         "Unknown panel %s %#06x, using conservative
timings\n",
                         vend, product_id);
                panel_edp_set_conservative_timings(panel, desc);
        } else {
                dev_info(dev, "Detected %s %s (%#06x)\n",
                         vend, panel->detected_panel->ident.name,
product_id);
                /* Update the delay; everything else comes from EDID */
                desc->delay = *panel->detected_panel->delay;
        }
```

Without this entry:
1. A **WARN_ON** fires in the kernel log (a kernel warning/splat) every
   boot on affected Dell/ASUS laptops
2. The panel falls back to **conservative timings** (`unprepare=2000ms`,
   `enable=200ms`) instead of the proper timings (`hpd_absent=200ms`,
   `unprepare=500ms`, `enable=50ms`), meaning **noticeably slower
   display initialization** with unnecessary delays
3. The WARN_ON trace in dmesg can confuse users and show up in automated
   bug reporting tools

### 5. SCOPE AND RISK ASSESSMENT

- **Lines changed**: 1 line added
- **Files changed**: 1 file
- **Risk**: Essentially zero. This is a pure data addition to a lookup
  table. It cannot affect any other panel or any other code path. The
  entry only matches when the EDID panel ID is exactly `AUO 0x0ba4`.
- **Dependencies**: None. Uses only existing macros and delay
  structures.

### 6. STABILITY INDICATORS

- **Reviewed-by**: Douglas Anderson (the panel-edp maintainer for
  ChromeOS/DRM)
- **Tested**: Author has the actual Dell Latitude 7455 hardware
- **Pattern**: Identical to dozens of other panel additions in this file
  (e.g., BOE NE14QDM for the same laptop was added similarly)

### 7. DEPENDENCY CHECK

No dependencies. The `EDP_PANEL_ENTRY` macro and `delay_200_500_e50`
structure have existed in the kernel for years, well before any current
stable tree branch points. This will apply cleanly to any stable tree
that has the panel-edp driver.

## Conclusion

This is a textbook example of a **device ID addition to an existing
driver** -- one of the explicitly allowed exception categories for
stable backports. It:

- Is a single-line data table entry with zero risk of regression
- Fixes a real user-visible issue (WARN_ON splat + degraded display
  timing on Dell Latitude 7455/7440 and some ASUS laptops)
- Uses only existing infrastructure (macro, delay structure)
- Has been reviewed by the subsystem maintainer
- Has been tested on real hardware
- Will apply cleanly to stable trees

**YES**

 drivers/gpu/drm/panel/panel-edp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
index 2c35970377431..85dd3f4cb8e1c 100644
--- a/drivers/gpu/drm/panel/panel-edp.c
+++ b/drivers/gpu/drm/panel/panel-edp.c
@@ -1880,6 +1880,7 @@ static const struct panel_delay delay_80_500_e50_d50 = {
  */
 static const struct edp_panel_entry edp_panels[] = {
 	EDP_PANEL_ENTRY('A', 'U', 'O', 0x04a4, &delay_200_500_e50, "B122UAN01.0"),
+	EDP_PANEL_ENTRY('A', 'U', 'O', 0x0ba4, &delay_200_500_e50, "B140QAX01.H"),
 	EDP_PANEL_ENTRY('A', 'U', 'O', 0x105c, &delay_200_500_e50, "B116XTN01.0"),
 	EDP_PANEL_ENTRY('A', 'U', 'O', 0x1062, &delay_200_500_e50, "B120XAN01.0"),
 	EDP_PANEL_ENTRY('A', 'U', 'O', 0x125c, &delay_200_500_e50, "Unknown"),
-- 
2.51.0