fix high_perf toggle noise and USB stall from blocking LFS

Root cause: each GAME+MIC toggle ran two synchronous Flash writes (hi_perf + dac_vol) in the 20ms timer, blocking AudioHwRemote2. Now apply DAC with brief mute only, defer hi_perf Flash, and skip redundant dac_vol save when user level unchanged.

Co-authored-by: Cursor <cursoragent@cursor.com>

sw_usb_audio/app_usb_aud_fosi_c1_v71/src/extensions/audiohw.xc

@@ -60,6 +60,8 @@ unsigned g_dnr_enable = 1;
 unsigned g_3d_enable = 1;
 /* 改动原因：GAME+MIC 高性能模式，0=DAC 在用户等级基础上减 6 格(约 -6dB)，1=不减；默认 0 */
 unsigned g_high_perf_mode = 0;
+/* 改动原因：high_perf 不在组合键回调里写 Flash，避免 lfs_init/deinit 阻塞导致 USB 卡死 */
+unsigned g_high_perf_save_pending = 0;
 unsigned g_led_mode = 0;
 unsigned g_fps_enable = 0;
 uint32_t get_reference_time();
@@ -598,6 +600,34 @@ static void tx1_apply_dac_hid_level(unsigned hid_level)
     SET_SHARED_GLOBAL(g_request_volume_set, 1);
 }
 
+/**
+ * 改动原因：high_perf 切换时直接写 0x0034，不经 g_request_volume_set，避免同 tick 再写 Flash。
+ */
+static void tx1_write_dac_hw_reg(unsigned eff_hid, unsigned reg,
+                                 unsigned &old_dac_vol,
+                                 client interface i2c_master_if i2c)
+{
+    SET_SHARED_GLOBAL(g_dac_vol, reg);
+    if (eff_hid == 0) {
+        unsafe { NAU88C22_REGWRITE(0x0034, 0x0000, i2c); }
+    } else {
+        unsafe {
+            NAU88C22_REGWRITE(0x0034, ((reg & 0xff) << 8) | (reg & 0xff), i2c);
+        }
+    }
+    old_dac_vol = reg;
+}
+
+static void tx1_apply_dac_hw_from_user_level(unsigned user_hid, unsigned high_perf,
+                                            unsigned &old_dac_vol,
+                                            client interface i2c_master_if i2c)
+{
+    unsigned eff_hid = tx1_effective_dac_hid_level(user_hid, high_perf);
+    unsigned reg = tx1_dac_reg_from_hid_level(eff_hid);
+
+    tx1_write_dac_hw_reg(eff_hid, reg, old_dac_vol, i2c);
+}
+
 /* 改动原因：统一把 MIC HID 等级写入 g_mic_volume_level/g_adc_vol，定时器请求分支 mic_volume 写 ADC 并 Flash */
 static void tx1_apply_mic_hid_level(unsigned hid_level)
 {
@@ -1425,6 +1455,8 @@ void AudioHwRemote2(streaming chanend c, chanend cc_mic_level, client interface
     unsigned factory_reset_6s_fired = 0;
     unsigned factory_reset_10s_fired = 0;
     unsigned factory_reset_done = 0;
+    /* 改动原因：仅用户真实改音量时写 tx1_dac_vol Flash；high_perf 切换不重写 */
+    unsigned last_saved_dac_hid = 255;
 
     // TX1 LED effect state for game mode indicators
     unsigned gpio_leds_dirty = 1;  // refresh LEDs on first tick
@@ -1491,6 +1523,7 @@ void AudioHwRemote2(streaming chanend c, chanend cc_mic_level, client interface
         }
         high_perf_mode = (unsigned)saved_hp;
         SET_SHARED_GLOBAL(g_high_perf_mode, high_perf_mode);
+        last_saved_dac_hid = (unsigned)saved_dac;
         tx1_apply_dac_hid_level((unsigned)saved_dac);
         tx1_apply_mic_hid_level((unsigned)saved_mic);
         feature_volume = tx1_hid_level_to_bar((unsigned)saved_mic);
@@ -1623,23 +1656,27 @@ void AudioHwRemote2(streaming chanend c, chanend cc_mic_level, client interface
                         if (user_hid <= TX1_DAC_HID_LEVEL_MAX) {
                             eff_hid = tx1_effective_dac_hid_level(user_hid, hp);
                             reg = tx1_dac_reg_from_hid_level(eff_hid);
-                            SET_SHARED_GLOBAL(g_dac_vol, reg);
+                            tx1_write_dac_hw_reg(eff_hid, reg, old_dac_vol, i2c);
-                            if (eff_hid == 0) {
+                            if (user_hid != last_saved_dac_hid) {
-                                unsafe { NAU88C22_REGWRITE(0x0034, 0x0000, i2c); }
-                            } else {
-                                /* 改动原因：必须用 SY102 查表值直写 0x0034，不能用 dac_volume 线性公式 */
-                                unsafe {
-                                    NAU88C22_REGWRITE(0x0034,
-                                        ((reg & 0xff) << 8) | (reg & 0xff), i2c);
-                                }
-                            }
-                            old_dac_vol = reg;
                                 tx1_save_dac_volume((unsigned char)user_hid);
+                                last_saved_dac_hid = user_hid;
+                            }
                             debug_printf("HID/panel SET_VOLUME: user_hid=%u eff_hid=%u hp=%u reg=0x%x\n",
                                          user_hid, eff_hid, hp, reg);
                         }
                     }
                 }
+                {
+                    unsigned hp_save;
+                    GET_SHARED_GLOBAL(hp_save, g_high_perf_save_pending);
+                    if (hp_save) {
+                        unsigned hp_val;
+                        GET_SHARED_GLOBAL(hp_val, g_high_perf_mode);
+                        tx1_save_high_perf_mode((unsigned char)hp_val);
+                        SET_SHARED_GLOBAL(g_high_perf_save_pending, 0);
+                        debug_printf("TX1: deferred save high_perf=%u\n", hp_val);
+                    }
+                }
                 {
                     unsigned req_mic;
                     GET_SHARED_GLOBAL(req_mic, g_request_mic_volume_set);
@@ -2187,12 +2224,19 @@ void AudioHwRemote2(streaming chanend c, chanend cc_mic_level, client interface
                     if (current_combo != COMBO_NONE && !combo_triggered) {
                         combo_triggered = 1;
                         if (current_combo == COMBO_GAME_MIC) {
+                            unsigned user_dac_hid;
+                            GET_SHARED_GLOBAL(user_dac_hid, g_volume_level);
                             high_perf_mode = !high_perf_mode;
                             SET_SHARED_GLOBAL(g_high_perf_mode, high_perf_mode);
-                            tx1_save_high_perf_mode((unsigned char)high_perf_mode);
+                            SET_SHARED_GLOBAL(g_high_perf_save_pending, 1);
-                            SET_SHARED_GLOBAL(g_request_volume_set, 1);
+                            /* 改动原因：先静音再改 0x0034，减轻 ±6dB 切换 pop；不写 Flash/不置 request_volume */
+                            tx1_amp_ctl_mute_force(led_if, TX1_AMP_CTL_MUTE_VAL);
+                            tx1_apply_dac_hw_from_user_level(user_dac_hid, high_perf_mode,
+                                                             old_dac_vol, i2c);
+                            tx1_amp_ctl_mute_force(led_if, TX1_AMP_CTL_UNMUTE_VAL);
                             gpio_leds_dirty = 1;
-                            debug_printf("TX1: GAME+MIC combo - high_perf_mode=%d\n", high_perf_mode);
+                            debug_printf("TX1: GAME+MIC combo - high_perf_mode=%d user_hid=%u\n",
+                                         high_perf_mode, user_dac_hid);
                         } else if (current_combo == COMBO_VOL_UP_DOWN) {
                             /* 改动原因：无 BYPASS 档；feature 空闲时 VOL 组合键可切换 RGB 装饰灯效 */
                             if (feature_mode == FEATURE_MODE_NONE) {