[U-Boot] [PATCH] arm64: zynqmp: Provide a config to not map DDR region in MMU table

[U-Boot] [PATCH] arm64: zynqmp: Provide a config to not map DDR region in MMU table

[Michal Simek]

From: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>

DDR less systems are possible for configuration like mini qspi
and making DDR region as normal memory may cause speculative
access which results u-boot hang if DDR is absent. So, this
patch fixes the issue by not making DDR memory region
entry into MMU table.

Future solution is to prepare MMU table per memory node in dts instead
of hard code DDR addresses.

Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
---

 arch/arm/cpu/armv8/zynqmp/Kconfig |  6 ++++++
 arch/arm/cpu/armv8/zynqmp/cpu.c   | 16 ++++++++++++----
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/arm/cpu/armv8/zynqmp/Kconfig b/arch/arm/cpu/armv8/zynqmp/Kconfig
index 3f922b4097a6..46de13054f26 100644
--- a/arch/arm/cpu/armv8/zynqmp/Kconfig
+++ b/arch/arm/cpu/armv8/zynqmp/Kconfig
@@ -68,6 +68,12 @@ config PMUFW_INIT_FILE
 config ZYNQMP_USB
 	bool "Configure ZynqMP USB"
 
+config ZYNQMP_NO_DDR
+	bool "Disable DDR MMU mapping"
+	help
+	  This option configures MMU with no DDR to avoid speculative
+	  access to DDR memory where DDR is not present.
+
 config SYS_MALLOC_F_LEN
 	default 0x600
 
diff --git a/arch/arm/cpu/armv8/zynqmp/cpu.c b/arch/arm/cpu/armv8/zynqmp/cpu.c
index 4596d6bff479..bc77dd03c361 100644
--- a/arch/arm/cpu/armv8/zynqmp/cpu.c
+++ b/arch/arm/cpu/armv8/zynqmp/cpu.c
@@ -17,20 +17,24 @@
 DECLARE_GLOBAL_DATA_PTR;
 
 static struct mm_region zynqmp_mem_map[] = {
+#if !defined(CONFIG_ZYNQMP_NO_DDR)
 	{
 		.virt = 0x0UL,
 		.phys = 0x0UL,
 		.size = 0x80000000UL,
 		.attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |
 			 PTE_BLOCK_INNER_SHARE
-	}, {
+	},
+#endif
+	{
 		.virt = 0x80000000UL,
 		.phys = 0x80000000UL,
 		.size = 0x70000000UL,
 		.attrs = PTE_BLOCK_MEMTYPE(MT_DEVICE_NGNRNE) |
 			 PTE_BLOCK_NON_SHARE |
 			 PTE_BLOCK_PXN | PTE_BLOCK_UXN
-	}, {
+	},
+	{
 		.virt = 0xf8000000UL,
 		.phys = 0xf8000000UL,
 		.size = 0x07e00000UL,
@@ -52,13 +56,17 @@ static struct mm_region zynqmp_mem_map[] = {
 		.attrs = PTE_BLOCK_MEMTYPE(MT_DEVICE_NGNRNE) |
 			 PTE_BLOCK_NON_SHARE |
 			 PTE_BLOCK_PXN | PTE_BLOCK_UXN
-	}, {
+	},
+#if !defined(CONFIG_ZYNQMP_NO_DDR)
+	{
 		.virt = 0x800000000UL,
 		.phys = 0x800000000UL,
 		.size = 0x800000000UL,
 		.attrs = PTE_BLOCK_MEMTYPE(MT_NORMAL) |
 			 PTE_BLOCK_INNER_SHARE
-	}, {
+	},
+#endif
+	{
 		.virt = 0x1000000000UL,
 		.phys = 0x1000000000UL,
 		.size = 0xf000000000UL,
-- 
1.9.1