[PATCH v1] ARM64: mmu: fix mmu_early_enable VA->PA mapping

[Lior Weintraub]

From 34dac7e73e486e864cfba5cee0e503a9641a502d Mon Sep 17 00:00:00 2001
From: Lior Weintraub <liorw at pliops.com>
Date: Mon, 18 Dec 2023 16:09:28 +0200
Subject: [PATCH v1] ARM64: mmu: fix mmu_early_enable VA->PA mapping

Fix the mmu_early_enable function to correctly map 40bits of virtual address into physical address with a 1:1 mapping.
It uses the init_range function to sets 2 table entries on TTB level0 and then fill level1 with the correct 1:1 mapping.

Signed-off-by: Lior Weintraub <liorw at pliops.com>
Tested-by: Ahmad Fatoum <a.fatoum at pengutronix.de> # Qemu ARM64 Virt
---
 arch/arm/cpu/mmu_64.c            | 16 +++++++++++++++-
 arch/arm/cpu/mmu_64.h            | 19 +++++++++++++++++--
 arch/arm/include/asm/pgtable64.h |  1 +
 3 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
index c6ea63e655..c47a744323 100644
--- a/arch/arm/cpu/mmu_64.c
+++ b/arch/arm/cpu/mmu_64.c
@@ -294,6 +294,18 @@ void dma_flush_range(void *ptr, size_t size)
 	v8_flush_dcache_range(start, end);
 }
 
+static void init_range(size_t total_level0_tables)
+{
+	uint64_t *ttb = get_ttb();
+	uint64_t addr = 0;
+	while(total_level0_tables--) {
+		early_remap_range(addr, L0_XLAT_SIZE, MAP_UNCACHED);
+		split_block(ttb,0);
+		addr += L0_XLAT_SIZE;
+		ttb++;
+	}
+}
+
 void mmu_early_enable(unsigned long membase, unsigned long memsize)
 {
 	int el;
@@ -308,7 +320,9 @@ void mmu_early_enable(unsigned long membase, unsigned long memsize)
 
 	memset((void *)ttb, 0, GRANULE_SIZE);
 
-	early_remap_range(0, 1UL << (BITS_PER_VA - 1), MAP_UNCACHED);
+	// Assume maximum BITS_PER_PA set to 40 bits.
+	// Set 1:1 mapping of VA->PA. So to cover the full 1TB range we need 2 tables.
+	init_range(2);
 	early_remap_range(membase, memsize - OPTEE_SIZE, MAP_CACHED);
 	early_remap_range(membase + memsize - OPTEE_SIZE, OPTEE_SIZE, MAP_FAULT);
 	early_remap_range(PAGE_ALIGN_DOWN((uintptr_t)_stext), PAGE_ALIGN(_etext - _stext), MAP_CACHED);
diff --git a/arch/arm/cpu/mmu_64.h b/arch/arm/cpu/mmu_64.h
index e4d81dace4..e3959e4407 100644
--- a/arch/arm/cpu/mmu_64.h
+++ b/arch/arm/cpu/mmu_64.h
@@ -105,12 +105,27 @@ static inline uint64_t level2mask(int level)
 	return mask;
 }
 
+/**
+ * @brief Returns the TCR (Translation Control Register) value
+ * 
+ * @param el - Exception Level
+ * @param va_bits - Virtual Address bits
+ * @return uint64_t TCR
+ */
 static inline uint64_t calc_tcr(int el, int va_bits)
 {
-	u64 ips;
-	u64 tcr;
+	u64 ips; // Intermediate Physical Address Size
+	u64 tcr; // Translation Control Register
 
+#if (BITS_PER_PA == 40)
 	ips = 2;
+#elif (BITS_PER_PA == 36)
+	ips = 1;
+#elif (BITS_PER_PA == 32)
+	ips = 0;
+#else
+#error "Unsupported"
+#endif
 
 	if (el == 1)
 		tcr = (ips << 32) | TCR_EPD1_DISABLE;
diff --git a/arch/arm/include/asm/pgtable64.h b/arch/arm/include/asm/pgtable64.h
index 21dac30cfe..b88ffe6be5 100644
--- a/arch/arm/include/asm/pgtable64.h
+++ b/arch/arm/include/asm/pgtable64.h
@@ -8,6 +8,7 @@
 
 #define VA_START                   0x0
 #define BITS_PER_VA                48
+#define BITS_PER_PA                40 // Use 40 Physical address bits
 
 /* Granule size of 4KB is being used */
 #define GRANULE_SIZE_SHIFT         12
-- 
2.40.0