From d786cf3aa747c71192a239f3606d3d7343869406 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Sun, 12 May 2024 16:48:43 +0200
Subject: [PATCH] ESS AudioDrive: Fix some regressions and implement DRQ
 setting in compatibility mode, fixes Windows 3.1x ES1688 drivers.

---
 src/sound/snd_sb.c     | 10 ++++++++--
 src/sound/snd_sb_dsp.c | 26 +++++++++++++++++++++++---
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/sound/snd_sb.c b/src/sound/snd_sb.c
index 80642adbe..364c01557 100644
--- a/src/sound/snd_sb.c
+++ b/src/sound/snd_sb.c
@@ -1492,7 +1492,8 @@ ess_mixer_write(uint16_t addr, uint8_t val, void *priv)
                     break;
 
                 case 0x64:
-                    mixer->regs[mixer->index] &= ~0x8;
+                    mixer->regs[mixer->index] = (mixer->regs[mixer->index] & 0xf7) | 0x20;
+                    // mixer->regs[mixer->index] &= ~0x8;
                     break;
 
                 case 0x40:
@@ -1615,9 +1616,13 @@ ess_mixer_read(uint16_t addr, void *priv)
                 ret = 0x0a;
             break;
 
+        case 0x48:
+            ret = mixer->regs[mixer->index];
+        break;
+
         /* Return 0x00 so it has bit 3 clear, so NT 5.x drivers don't misdetect it as ES1788. */
         case 0x64:
-            ret = 0x00;
+            ret = (mixer->regs[mixer->index] & 0xf7) | 0x20;
             break;
 
         default:
@@ -3463,6 +3468,7 @@ ess_x688_init(UNUSED(const device_t *info))
     }
 
     ess->mixer_enabled = 1;
+    ess->mixer_ess.regs[0x40] = 0x0a;
     io_sethandler(addr + 4, 0x0002,
                   ess_mixer_read, NULL, NULL,
                   ess_mixer_write, NULL, NULL,
diff --git a/src/sound/snd_sb_dsp.c b/src/sound/snd_sb_dsp.c
index 9c148339d..e5c2359a0 100644
--- a/src/sound/snd_sb_dsp.c
+++ b/src/sound/snd_sb_dsp.c
@@ -563,6 +563,8 @@ sb_start_dma(sb_dsp_t *dsp, int dma8, int autoinit, uint8_t format, int len)
             timer_set_delay_u64(&dsp->output_timer, (uint64_t) dsp->sblatcho);
         dsp->sbleftright = dsp->sbleftright_default;
         dsp->sbdacpos    = 0;
+
+        dma_set_drq(dsp->sb_8_dmanum, 1);
     } else {
         dsp->sb_16_length = dsp->sb_16_origlength = len;
         dsp->sb_16_format                         = format;
@@ -574,6 +576,11 @@ sb_start_dma(sb_dsp_t *dsp, int dma8, int autoinit, uint8_t format, int len)
         dsp->sb_16_output = 1;
         if (!timer_is_enabled(&dsp->output_timer))
             timer_set_delay_u64(&dsp->output_timer, (uint64_t) dsp->sblatcho);
+
+        if (dsp->sb_16_dma_supported)
+            dma_set_drq(dsp->sb_16_dmanum, 1);
+        else
+            dma_set_drq(dsp->sb_16_8_dmanum, 1);
     }
 
     /* This will be set later for ESS playback/record modes. */
@@ -594,6 +601,8 @@ sb_start_dma_i(sb_dsp_t *dsp, int dma8, int autoinit, uint8_t format, int len)
         dsp->sb_8_output = 0;
         if (!timer_is_enabled(&dsp->input_timer))
             timer_set_delay_u64(&dsp->input_timer, (uint64_t) dsp->sblatchi);
+
+        dma_set_drq(dsp->sb_8_dmanum, 1);
     } else {
         dsp->sb_16_length = dsp->sb_16_origlength = len;
         dsp->sb_16_format                         = format;
@@ -605,6 +614,11 @@ sb_start_dma_i(sb_dsp_t *dsp, int dma8, int autoinit, uint8_t format, int len)
         dsp->sb_16_output = 0;
         if (!timer_is_enabled(&dsp->input_timer))
             timer_set_delay_u64(&dsp->input_timer, (uint64_t) dsp->sblatchi);
+
+        if (dsp->sb_16_dma_supported)
+            dma_set_drq(dsp->sb_16_dmanum, 1);
+        else
+            dma_set_drq(dsp->sb_16_8_dmanum, 1);
     }
 
     memset(dsp->record_buffer, 0, sizeof(dsp->record_buffer));
@@ -771,7 +785,10 @@ sb_16_write_dma(void *priv, uint16_t val)
 void
 sb_ess_update_irq_drq_readback_regs(sb_dsp_t *dsp, bool legacy)
 {
-    uint8_t t = 0x00;
+    sb_t        *ess   = (sb_t *) dsp->parent;
+    ess_mixer_t *mixer = &ess->mixer_ess;
+    uint8_t      t     = 0x00;
+
     /* IRQ control */
     if (legacy) {
         t |= 0x80;
@@ -779,6 +796,7 @@ sb_ess_update_irq_drq_readback_regs(sb_dsp_t *dsp, bool legacy)
     switch (dsp->sb_irqnum) {
         default:
             break;
+        case 2:
         case 9:
             t |= 0x0;
             break;
@@ -793,6 +811,8 @@ sb_ess_update_irq_drq_readback_regs(sb_dsp_t *dsp, bool legacy)
             break;
     }
     ESSreg(0xB1) = (ESSreg(0xB1) & 0xF0) | t;
+    if ((mixer != NULL) && (ess->mpu != NULL) && (((mixer->regs[0x40] >> 5) & 0x7) == 2))
+        mpu401_setirq(ess->mpu, ess->dsp.sb_irqnum);
 
     /* DRQ control */
     t = 0x00;
@@ -1802,7 +1822,7 @@ sb_read(uint16_t a, void *priv)
 
     switch (a & 0xf) {
         case 0x6:
-            ret = 0xff;
+            ret = IS_ESS(dsp) ? 0x00 : 0xff;
             break;
         case 0xA: /* Read data */
             if (dsp->mpu && dsp->uart_midi)
@@ -1821,7 +1841,7 @@ sb_read(uint16_t a, void *priv)
                 dsp->state = DSP_S_NORMAL;
             break;
         case 0xC: /* Write data ready */
-            if (dsp->state == DSP_S_NORMAL) {
+            if ((dsp->state == DSP_S_NORMAL) || IS_ESS(dsp)) {
                 if (dsp->sb_8_enable || dsp->sb_type >= SB16)
                     dsp->busy_count = (dsp->busy_count + 1) & 3;
                 else