[PATCH -next v6 07/10] arm: armv8: mmu: add mmu_unmap_reserved_mem

[Anshul Dalal]

For armv8, U-Boot uses a static map defined as 'mem_map' for configuring
the MMU's page tables, done by mmu_setup.

Though this works well for simpler platforms, it makes creating runtime
carveouts by modifying the static array at runtime exceedingly complex
like in mach-snapdragon/board.c.

Creation of such carveouts are much better handled by APIs such as
mmu_change_region_attr once the page tables are configured. Usually such
carveouts are configured via the device-tree's reserved-memory node
which provides the address and size for the carveout.

Therefore this patch adds mmu_unmap_reserved_mem which acts as a wrapper
over mmu_change_region_attr, helping unmap a reserved-memory region.

Signed-off-by: Anshul Dalal <anshuld at ti.com>
---
 arch/arm/cpu/armv8/cache_v8.c    | 23 +++++++++++++++++++++++
 arch/arm/include/asm/armv8/mmu.h |  9 +++++++++
 2 files changed, 32 insertions(+)

diff --git a/arch/arm/cpu/armv8/cache_v8.c b/arch/arm/cpu/armv8/cache_v8.c
index edb895da1f2..66969f4ea9b 100644
--- a/arch/arm/cpu/armv8/cache_v8.c
+++ b/arch/arm/cpu/armv8/cache_v8.c
@@ -85,6 +85,29 @@ int mem_map_fix_dram_banks(unsigned int index, unsigned int len, u64 attrs)
 
 	return 0;
 }
+
+int mmu_unmap_reserved_mem(const char *name)
+{
+	void *fdt = (void *)gd->fdt_blob;
+	char node_path[128];
+	fdt_addr_t addr;
+	fdt_size_t size;
+	int ret;
+
+	snprintf(node_path, sizeof(node_path), "/reserved-memory/%s", name);
+	ret = fdt_path_offset(fdt, node_path);
+	if (ret < 0)
+		return ret;
+
+	addr = fdtdec_get_addr_size(fdt, ret, "reg", &size);
+	if (addr == FDT_ADDR_T_NONE)
+		return -1;
+
+	mmu_change_region_attr(addr, size, PTE_TYPE_FAULT);
+
+	return 0;
+}
+
 u64 get_tcr(u64 *pips, u64 *pva_bits)
 {
 	int el = get_effective_el();
diff --git a/arch/arm/include/asm/armv8/mmu.h b/arch/arm/include/asm/armv8/mmu.h
index 257352f216e..fbd64e649ff 100644
--- a/arch/arm/include/asm/armv8/mmu.h
+++ b/arch/arm/include/asm/armv8/mmu.h
@@ -206,6 +206,15 @@ void setup_pgtables(void);
  * @len: The size of mem_map
  */
 int mem_map_fix_dram_banks(unsigned int index, unsigned int len, u64 attrs);
+
+/**
+ * mmu_unmap_reserved_mem() - Unmaps a reserved-memory node as PTE_TYPE_FAULT
+ * once MMU is configured by mmu_setup.
+ *
+ * @name: The name of the node under "/reserved-memory/" path
+ */
+int mmu_unmap_reserved_mem(const char *name);
+
 u64 get_tcr(u64 *pips, u64 *pva_bits);
 
 /**
-- 
2.50.1