From 76957e502d16b845cf4b850b9ddd8ddcd723e4e6 Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Mon, 7 Sep 2020 21:41:03 -0700
Subject: [PATCH] kern: add build-define for logging to iram ringbuffer

---
 .../kern_debug_log_impl.board.nintendo_nx.cpp | 50 +++++++++++++++++++
 ...kern_k_memory_layout.board.nintendo_nx.cpp |  2 +
 2 files changed, 52 insertions(+)

diff --git a/libraries/libmesosphere/source/kern_debug_log_impl.board.nintendo_nx.cpp b/libraries/libmesosphere/source/kern_debug_log_impl.board.nintendo_nx.cpp
index cb6d095b9..0f54d3361 100644
--- a/libraries/libmesosphere/source/kern_debug_log_impl.board.nintendo_nx.cpp
+++ b/libraries/libmesosphere/source/kern_debug_log_impl.board.nintendo_nx.cpp
@@ -18,6 +18,8 @@
 
 namespace ams::kern {
 
+#if defined(MESOSPHERE_DEBUG_LOG_USE_UART_A) || defined(MESOSPHERE_DEBUG_LOG_USE_UART_B) || defined(MESOSPHERE_DEBUG_LOG_USE_UART_C) || defined(MESOSPHERE_DEBUG_LOG_USE_UART_D)
+
     namespace {
 
         enum UartRegister {
@@ -138,4 +140,52 @@ namespace ams::kern {
         ReadUartRegister(UartRegister_FCR);
     }
 
+#elif defined(MESOSPHERE_DEBUG_LOG_USE_IRAM_RINGBUFFER)
+
+    namespace {
+
+        constinit KVirtualAddress g_debug_iram_address = 0;
+
+        constexpr size_t RingBufferSize = 0x5000;
+        constinit uintptr_t g_offset = 0;
+
+        constinit u8 g_saved_buffer[RingBufferSize];
+
+    }
+
+    bool KDebugLogImpl::Initialize() {
+        /* Set the base address. */
+        g_debug_iram_address = KMemoryLayout::GetDeviceVirtualAddress(KMemoryRegionType_LegacyLpsIram) + 0x38000;
+
+        std::memset(GetVoidPointer(g_debug_iram_address), 0xFF, RingBufferSize);
+
+        return true;
+    }
+
+    void KDebugLogImpl::PutChar(char c) {
+        GetPointer<char>(g_debug_iram_address)[g_offset++] = c;
+
+        if (g_offset == RingBufferSize) {
+            g_offset = 0;
+        }
+    }
+
+    void KDebugLogImpl::Flush() {
+        /* ... */
+    }
+
+    void KDebugLogImpl::Save() {
+        std::memcpy(g_saved_buffer, GetVoidPointer(g_debug_iram_address), RingBufferSize);
+    }
+
+    void KDebugLogImpl::Restore() {
+        std::memcpy(GetVoidPointer(g_debug_iram_address), g_saved_buffer, RingBufferSize);
+    }
+
+#else
+
+    #error "Unknown Debug UART device!"
+
+#endif
+
 }
diff --git a/libraries/libmesosphere/source/kern_k_memory_layout.board.nintendo_nx.cpp b/libraries/libmesosphere/source/kern_k_memory_layout.board.nintendo_nx.cpp
index 5112c9ac0..d3a98cc62 100644
--- a/libraries/libmesosphere/source/kern_k_memory_layout.board.nintendo_nx.cpp
+++ b/libraries/libmesosphere/source/kern_k_memory_layout.board.nintendo_nx.cpp
@@ -34,6 +34,8 @@ namespace ams::kern {
                 return KMemoryLayout::GetPhysicalMemoryRegionTree().Insert(0x70006200, 0x100, KMemoryRegionType_Uart | KMemoryRegionAttr_ShouldKernelMap);
             #elif defined(MESOSPHERE_DEBUG_LOG_USE_UART_D)
                 return KMemoryLayout::GetPhysicalMemoryRegionTree().Insert(0x70006300, 0x100, KMemoryRegionType_Uart | KMemoryRegionAttr_ShouldKernelMap);
+            #elif defined(MESOSPHERE_DEBUG_LOG_USE_IRAM_RINGBUFFER)
+                return true;
             #else
                 #error "Unknown Debug UART device!"
             #endif