From 4d81ddab4f72221634919bf8f8c8473d558a3d79 Mon Sep 17 00:00:00 2001
From: David Karoly <karolyd577@gmail.com>
Date: Wed, 20 Oct 2021 18:48:42 +0200
Subject: [PATCH] boot/efi: initialize mmu for arm

Change-Id: I918a459dfb4e5d0864ae4c8b806df059248d43b6
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4630
Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
---
 .../boot/platform/efi/arch/arm/arch_start.cpp | 11 ++++--
 src/system/boot/platform/efi/arch/arm/entry.S | 38 +++++++++++++++----
 2 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/src/system/boot/platform/efi/arch/arm/arch_start.cpp b/src/system/boot/platform/efi/arch/arm/arch_start.cpp
index 265c0ec9c7..e6ea75b8e4 100644
--- a/src/system/boot/platform/efi/arch/arm/arch_start.cpp
+++ b/src/system/boot/platform/efi/arch/arm/arch_start.cpp
@@ -11,7 +11,7 @@
 #include "efi_platform.h"
 
 
-extern "C" void arch_enter_kernel(struct kernel_args *kernelArgs,
+extern "C" void arch_enter_kernel(uint32_t ttbr, struct kernel_args *kernelArgs,
 	addr_t kernelEntry, addr_t kernelStackTop);
 
 // From arch_mmu.cpp
@@ -68,7 +68,7 @@ arch_start_kernel(addr_t kernelEntry)
 	}
 
 	// Generate page tables for use after ExitBootServices.
-	arch_mmu_generate_post_efi_page_tables(
+	uint32_t final_ttbr0 = arch_mmu_generate_post_efi_page_tables(
 		memory_map_size, memory_map, descriptor_size, descriptor_version);
 
 	// Attempt to fetch the memory map and exit boot services.
@@ -106,6 +106,11 @@ arch_start_kernel(addr_t kernelEntry)
 	//smp_boot_other_cpus(final_pml4, kernelEntry);
 
 	// Enter the kernel!
-	arch_enter_kernel(&gKernelArgs, kernelEntry,
+	dprintf("arch_enter_kernel(ttbr0: 0x%08x, kernelArgs: 0x%08x, "
+		"kernelEntry: 0x%08x, sp: 0x%08x)\n",
+		final_ttbr0, (uint32_t)&gKernelArgs, (uint32_t)&kernelEntry,
+		(uint32_t)(gKernelArgs.cpu_kstack[0].start + gKernelArgs.cpu_kstack[0].size));
+
+	arch_enter_kernel(final_ttbr0, &gKernelArgs, kernelEntry,
 		gKernelArgs.cpu_kstack[0].start + gKernelArgs.cpu_kstack[0].size);
 }
diff --git a/src/system/boot/platform/efi/arch/arm/entry.S b/src/system/boot/platform/efi/arch/arm/entry.S
index d8ea332dcf..49930196a6 100644
--- a/src/system/boot/platform/efi/arch/arm/entry.S
+++ b/src/system/boot/platform/efi/arch/arm/entry.S
@@ -8,23 +8,45 @@
 
 	.text
 
-/*	status_t arch_enter_kernel(struct kernel_args *kernelArgs,
+/*	status_t arch_enter_kernel(uint32_t ttbr, struct kernel_args *kernelArgs,
 		addr_t kernelEntry, addr_t kernelStackTop);
 
-	r0	- kernelArgs
-	r1	- kernelEntry
-	r2	- kernelStackTop
+	r0	- ttbr
+	r1	- kernelArgs
+	r2	- kernelEntry
+	r3	- kernelStackTop
 */
 FUNCTION(arch_enter_kernel):
 
-	// set the kernel stack
-	mov		sp,r2
+
+	mov		r5,r0
+	mov		r4,r2
 
 	// set up kernel _start args
-	//mov	r0,r0	// kernelArgs
-	mov		r4,r1
+	mov		r0,r1	// kernelArgs
 	mov		r1,#0	// currentCPU=0
 
+	// flush TLB
+	MCR p15, 0, r1, c8, c7, 0
+
+	// set TTBR0
+	MCR p15, 0, r5, c2, c0, 0
+
+	// flush TLB (again)
+	MCR p15, 0, r1, c8, c7, 0
+
+	// write DACR
+	mov r9, #0xffffffff
+	MCR p15, 0, r9, c3, c0, 0
+
+	// enable MMU
+	MRC p15, 0, r9, c1, c0, 0
+	orr r9, r9, #1
+	MCR p15, 0, r9, c1, c0, 0
+
+	// set the kernel stack
+	mov		sp,r3
+
 	// call the kernel
 	mov		pc,r4