From 781a28f3edae01cce79499936c331979b592194b Mon Sep 17 00:00:00 2001
From: Andreas Kling <awesomekling@gmail.com>
Date: Sat, 13 Jul 2019 17:08:45 +0200
Subject: [PATCH] SB16: Switch to signed 16-bit 44100 Hz Mono by default.

We should switch to Stereo but I'm having some trouble with that locally..
Since we intend to mix everything through SoundServer, let's just put the
card into 16-bit mode right away.
---
 Kernel/Devices/SB16.cpp | 38 ++++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/Kernel/Devices/SB16.cpp b/Kernel/Devices/SB16.cpp
index aad5a724e3f..b2696427887 100644
--- a/Kernel/Devices/SB16.cpp
+++ b/Kernel/Devices/SB16.cpp
@@ -2,6 +2,13 @@
 #include "IO.h"
 #include <Kernel/VM/MemoryManager.h>
 
+//#define SB16_DEBUG
+
+enum class SampleFormat : u8 {
+    Signed = 0x10,
+    Stereo = 0x20,
+};
+
 const u16 DSP_READ = 0x22A;
 const u16 DSP_WRITE = 0x22C;
 const u16 DSP_STATUS = 0x22E;
@@ -101,31 +108,31 @@ ssize_t SB16::read(FileDescription&, u8*, ssize_t)
 void SB16::dma_start(uint32_t length)
 {
     const auto addr = m_dma_buffer_page->paddr().get();
-    const u8 channel = 1;
+    const u8 channel = 5; // 16-bit samples use DMA channel 5 (on the master DMA controller)
     const u8 mode = 0;
 
     // Disable the DMA channel
-    IO::out8(0x0a, 4 + (channel % 4));
+    IO::out8(0xd4, 4 + (channel % 4));
 
     // Clear the byte pointer flip-flop
-    IO::out8(0x0c, 0);
+    IO::out8(0xd8, 0);
 
     // Write the DMA mode for the transfer
-    IO::out8(0x0b, channel | mode);
+    IO::out8(0xd6, (channel % 4) | mode);
 
     // Write the offset of the buffer
-    IO::out8(0x02, (u8)addr);
-    IO::out8(0x02, (u8)(addr >> 8));
+    IO::out8(0xc4, (u8)addr);
+    IO::out8(0xc4, (u8)(addr >> 8));
 
     // Write the transfer length
-    IO::out8(0x03, (u8)(length - 1));
-    IO::out8(0x03, (u8)((length - 1) >> 8));
+    IO::out8(0xc6, (u8)(length - 1));
+    IO::out8(0xc6, (u8)((length - 1) >> 8));
 
     // Write the buffer
-    IO::out8(0x83, addr >> 16);
+    IO::out8(0x8b, addr >> 16);
 
     // Enable the DMA channel
-    IO::out8(0x0a, channel);
+    IO::out8(0xd4, (channel % 4));
 }
 
 void SB16::wait_for_irq()
@@ -142,7 +149,6 @@ void SB16::wait_for_irq()
 #ifdef SB16_DEBUG
     kprintf("SB16: got interrupt!\n");
 #endif
-    memory_barrier();
 }
 
 ssize_t SB16::write(FileDescription&, const u8* data, ssize_t length)
@@ -153,20 +159,24 @@ ssize_t SB16::write(FileDescription&, const u8* data, ssize_t length)
     }
 
     kprintf("SB16: Writing buffer of %d bytes\n", length);
+    ASSERT(length <= PAGE_SIZE);
     const int BLOCK_SIZE = 32 * 1024;
     if (length > BLOCK_SIZE) {
         return -ENOSPC;
     }
-    const u8 mode = 0;
+
+    u8 mode = (u8)SampleFormat::Signed;
 
     disable_irq();
     const int sample_rate = 44100;
     set_sample_rate(sample_rate);
-    dma_start(length);
     memcpy(m_dma_buffer_page->paddr().as_ptr(), data, length);
+    dma_start(length);
 
     u8 command = 0x06;
-    command |= 0xc0;
+
+    // Send 16-bit samples.
+    command |= 0xb0;
 
     dsp_write(command);
     dsp_write(mode);