touch: retry + hard-reset when FT5426 boots into wedged 0xff state

After a long bench session of taps + power cycles, the FT5426 on this
unit started returning dev_mode=0xff on every read. The polling loop
interpreted that as 15 simultaneous touches forever (td_status bits
0..3 all set), wedged `was_down=true` permanently, and no tap or
long-press ever fired — the screen looked dead.

Two layers of defence in touch_init:
  1. retry the dev_mode read up to 10 × 30 ms in case the chip is just
     slow to come up after PC_RST_TP_N is released.
  2. if still stuck, pulse PC_RST_TP_N via a new
     display_touch_reset_pulse() helper (drop reset for 20 ms then
     release + 50 ms settle), then retry the read another 10 × 30 ms.

Plus a polling-loop sanity check: an FT5x06 supports max 5 simultaneous
points, so a TD_STATUS lower-nibble value > 5 is bogus and the poll
cycle is skipped. That keeps a wedged chip from producing phantom
"15 touches" reports if it slips into 0xff during runtime.

If both attempts still report 0xff, we log loudly and let the polling
task run — it harmlessly drops cycles via the >5 sanity check. Wake
still works via POST /state from Scrypted; this only disables touch
gestures on a hardware-stuck boot.

3 files changed, 48 insertions, 2 deletions

diff --git a/main/display.c b/main/display.c
index a704891..8c5ffb2 100644
--- a/main/display.c
+++ b/main/display.c
@@ -218,6 +218,22 @@ static esp_err_t touch_release_reset(void)
         PC_LED_EN | PC_RST_TP_N | PC_RST_LCD_N | PC_RST_BRIDGE_N);
 }
 
+// Hard-reset the touch IC: drop PC_RST_TP_N for ~20 ms, then release.
+// touch_init() calls this if its dev_mode read keeps returning 0xff —
+// usually unwedges a stuck FT5426 without needing a power cycle.
+esp_err_t display_touch_reset_pulse(void)
+{
+    if (!s_panel_mcu) return ESP_ERR_INVALID_STATE;
+    // Hold touch in reset (clear PC_RST_TP_N), keep everything else as-is.
+    esp_err_t err = mcu_write_u8(REG_PORTC,
+        PC_LED_EN | PC_RST_LCD_N | PC_RST_BRIDGE_N);
+    if (err != ESP_OK) return err;
+    vTaskDelay(pdMS_TO_TICKS(20));
+    err = touch_release_reset();
+    vTaskDelay(pdMS_TO_TICKS(50));
+    return err;
+}
+
 // ============================================================================
 // TC358762 bridge configuration (DSI Generic Long Write packets)
 // Sequence mirrors Linux drivers/gpu/drm/bridge/tc358762.c tc358762_init().
diff --git a/main/display.h b/main/display.h
index 9092efb..cb2b913 100644
--- a/main/display.h
+++ b/main/display.h
@@ -27,6 +27,11 @@ esp_err_t display_set_brightness(uint8_t brightness_0_100);
 esp_err_t display_sleep(void);
 esp_err_t display_wake(void);
 
+// Pulse the touch IC's reset line (PC_RST_TP_N) via the panel MCU. Used
+// by touch_init() when the FT5426 boots into a wedged state and refuses
+// to leave dev_mode=0xff.
+esp_err_t display_touch_reset_pulse(void);
+
 // Blit an RGB565 source image to the panel, applying the current
 // orientation. Source dimensions must match the effective resolution:
 //   portrait  -> src is 480x800 (rotated 90° CW into the 800x480 panel)
diff --git a/main/touch.c b/main/touch.c
index 7cde4bf..6f91665 100644
--- a/main/touch.c
+++ b/main/touch.c
@@ -67,6 +67,10 @@ static void touch_task(void *arg)
 
         if (ft_read(FT_REG_DEV_MODE, buf, sizeof(buf)) != ESP_OK) continue;
         uint8_t touches = buf[FT_REG_TD_STATUS] & 0x0F;
+        // FT5x06 supports max 5 simultaneous points. A reading above that
+        // is bogus (typically the bus is parking 0xff because the IC isn't
+        // responding) — drop the cycle to avoid faking a phantom press.
+        if (touches > 5) continue;
         uint64_t now    = (uint64_t)esp_timer_get_time();
 
         if (touches > 0) {
@@ -112,12 +116,33 @@ esp_err_t touch_init(void)
     ESP_RETURN_ON_ERROR(i2c_master_bus_add_device(bus, &cfg, &s_dev),
                        TAG, "i2c add FT5426");
 
-    uint8_t dev_mode = 0;
-    esp_err_t err = ft_read(FT_REG_DEV_MODE, &dev_mode, 1);
+    // FT5426 sometimes returns 0xff on the first read after its reset is
+    // released (especially on cold boot before its internal firmware has
+    // finished booting). 0xff causes the polling loop to misread 15
+    // touches forever. Two-stage recovery: short wait + retry, then a
+    // hard reset pulse via the panel MCU if that still doesn't help.
+    uint8_t dev_mode = 0xff;
+    esp_err_t err = ESP_FAIL;
+    for (int attempt = 0; attempt < 2; ++attempt) {
+        for (int i = 0; i < 10; ++i) {
+            err = ft_read(FT_REG_DEV_MODE, &dev_mode, 1);
+            if (err == ESP_OK && dev_mode != 0xff) break;
+            vTaskDelay(pdMS_TO_TICKS(30));
+        }
+        if (err == ESP_OK && dev_mode != 0xff) break;
+        if (attempt == 0) {
+            ESP_LOGW(TAG, "FT5426 stuck at 0xff — pulsing PC_RST_TP_N");
+            display_touch_reset_pulse();
+        }
+    }
     if (err != ESP_OK) {
         ESP_LOGE(TAG, "FT5426 @0x38 unreachable (%s)", esp_err_to_name(err));
         return err;
     }
+    if (dev_mode == 0xff) {
+        ESP_LOGW(TAG, "FT5426 still stuck after hard reset — touch will "
+                      "not register; tap/long-press disabled this boot");
+    }
     ESP_LOGI(TAG, "FT5426 ack'd (dev_mode=0x%02x); "
                   "tap=toggle wake/sleep, %dms hold=info overlay",
              dev_mode, LONG_PRESS_MS);