ARC: mm: Decouple RAM base address from kernel link address

	[Needed for HSDK]

Currently the first page of system (hence RAM base) is assumed to be
@ CONFIG_LINUX_LINK_BASE, where kernel itself is linked.

However is case of HSDK platform, for reasons explained in that patch,
this is not true. kernel needs to be linked @ 0x9000_0000 while DDR
is still wired at 0x8000_0000. To properly account for this 256M of RAM,
we need to introduce a new option and base page frame accountiing off of
it.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: renamed  CONFIG_KERNEL_RAM_BASE_ADDRESS => CONFIG_LINUX_RAM_BASE
       : simplified changelog]

8 files changed, 18 insertions, 10 deletions

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 7db85ab00c52..65b7549e17db 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -418,7 +418,7 @@ endif	# ISA_ARCV2
 endmenu   # "ARC CPU Configuration"
 
 config LINUX_LINK_BASE
-        hex "Linux Link Address"
+        hex "Kernel link address"
         default "0x80000000"
         help
           ARC700 divides the 32 bit phy address space into two equal halves
@@ -431,6 +431,14 @@ config LINUX_LINK_BASE
           If you don't know what the above means, leave this setting alone.
           This needs to match memory start address specified in Device Tree
 
+config LINUX_RAM_BASE
+        hex "RAM base address"
+        default LINUX_LINK_BASE
+        help
+          By default Linux is linked at base of RAM. However in some special
+          cases (such as HSDK), Linux can't be linked at start of DDR, hence
+          this option.
+
 config HIGHMEM
         bool "High Memory Support"
         select ARCH_DISCONTIGMEM_ENABLE
diff --git a/arch/arc/boot/dts/axc001.dtsi b/arch/arc/boot/dts/axc001.dtsi
index a380ffa1a458..fdc266504ada 100644
--- a/arch/arc/boot/dts/axc001.dtsi
+++ b/arch/arc/boot/dts/axc001.dtsi
@@ -99,7 +99,7 @@
 
         memory {
                 device_type = "memory";
-                /* CONFIG_KERNEL_RAM_BASE_ADDRESS needs to match low mem start */
+                /* CONFIG_LINUX_RAM_BASE needs to match low mem start */
                 reg = <0x0 0x80000000 0x0 0x1b000000>;  /* (512 - 32) MiB */
         };
 
diff --git a/arch/arc/boot/dts/axc003.dtsi b/arch/arc/boot/dts/axc003.dtsi
index dca7e39409be..4e6e9f57e790 100644
--- a/arch/arc/boot/dts/axc003.dtsi
+++ b/arch/arc/boot/dts/axc003.dtsi
@@ -109,7 +109,7 @@
 
         memory {
                 device_type = "memory";
-                /* CONFIG_KERNEL_RAM_BASE_ADDRESS needs to match low mem start */
+                /* CONFIG_LINUX_RAM_BASE needs to match low mem start */
                 reg = <0x0 0x80000000 0x0 0x20000000    /* 512 MiB low mem */
                        0x1 0xc0000000 0x0 0x40000000>;  /* 1 GiB highmem */
         };
diff --git a/arch/arc/boot/dts/axc003_idu.dtsi b/arch/arc/boot/dts/axc003_idu.dtsi
index 5b56beffc1c5..63954a8b0100 100644
--- a/arch/arc/boot/dts/axc003_idu.dtsi
+++ b/arch/arc/boot/dts/axc003_idu.dtsi
@@ -115,7 +115,7 @@
 
         memory {
                 device_type = "memory";
-                /* CONFIG_KERNEL_RAM_BASE_ADDRESS needs to match low mem start */
+                /* CONFIG_LINUX_RAM_BASE needs to match low mem start */
                 reg = <0x0 0x80000000 0x0 0x20000000    /* 512 MiB low mem */
                        0x1 0xc0000000 0x0 0x40000000>;  /* 1 GiB highmem */
         };
diff --git a/arch/arc/boot/dts/nsim_hs.dts b/arch/arc/boot/dts/nsim_hs.dts
index 3772c40c245e..8d787b251f73 100644
--- a/arch/arc/boot/dts/nsim_hs.dts
+++ b/arch/arc/boot/dts/nsim_hs.dts
@@ -18,7 +18,7 @@
 
         memory {
                 device_type = "memory";
-                /* CONFIG_LINUX_LINK_BASE needs to match low mem start */
+                /* CONFIG_LINUX_RAM_BASE needs to match low mem start */
                 reg = <0x0 0x80000000 0x0 0x20000000    /* 512 MB low mem */
                        0x1 0x00000000 0x0 0x40000000>;  /* 1 GB highmem */
         };
diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
index 296c3426a6ad..109baa06831c 100644
--- a/arch/arc/include/asm/page.h
+++ b/arch/arc/include/asm/page.h
@@ -85,7 +85,7 @@ typedef pte_t * pgtable_t;
  */
 #define virt_to_pfn(kaddr)      (__pa(kaddr) >> PAGE_SHIFT)
 
-#define ARCH_PFN_OFFSET         virt_to_pfn(CONFIG_LINUX_LINK_BASE)
+#define ARCH_PFN_OFFSET         virt_to_pfn(CONFIG_LINUX_RAM_BASE)
 
 #ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn)          (((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
diff --git a/arch/arc/mm/cache.c b/arch/arc/mm/cache.c
index d68d36c15909..eee924dfffa6 100644
--- a/arch/arc/mm/cache.c
+++ b/arch/arc/mm/cache.c
@@ -1173,7 +1173,7 @@ noinline void __init arc_ioc_setup(void)
         write_aux_reg(ARC_REG_IO_COH_AP0_SIZE, order_base_2(mem_sz >> 10) - 2);
 
         /* for now assume kernel base is start of IOC aperture */
-        ioc_base = CONFIG_LINUX_LINK_BASE;
+        ioc_base = CONFIG_LINUX_RAM_BASE;
 
         if (ioc_base % mem_sz != 0)
                 panic("IOC Aperture start must be aligned to the size of the aperture");
diff --git a/arch/arc/mm/init.c b/arch/arc/mm/init.c
index 8c9415ed6280..ba145065c579 100644
--- a/arch/arc/mm/init.c
+++ b/arch/arc/mm/init.c
@@ -26,7 +26,7 @@ pgd_t swapper_pg_dir[PTRS_PER_PGD] __aligned(PAGE_SIZE);
 char empty_zero_page[PAGE_SIZE] __aligned(PAGE_SIZE);
 EXPORT_SYMBOL(empty_zero_page);
 
-static const unsigned long low_mem_start = CONFIG_LINUX_LINK_BASE;
+static const unsigned long low_mem_start = CONFIG_LINUX_RAM_BASE;
 static unsigned long low_mem_sz;
 
 #ifdef CONFIG_HIGHMEM
@@ -63,7 +63,7 @@ void __init early_init_dt_add_memory_arch(u64 base, u64 size)
 
         if (!low_mem_sz) {
                 if (base != low_mem_start)
-                        panic("CONFIG_LINUX_LINK_BASE != DT memory { }");
+                        panic("CONFIG_LINUX_RAM_BASE != DT memory { }");
 
                 low_mem_sz = size;
                 in_use = 1;
@@ -161,7 +161,7 @@ void __init setup_arch_memory(void)
          * We can't use the helper free_area_init(zones[]) because it uses
          * PAGE_OFFSET to compute the @min_low_pfn which would be wrong
          * when our kernel doesn't start at PAGE_OFFSET, i.e.
-         * PAGE_OFFSET != CONFIG_LINUX_LINK_BASE
+         * PAGE_OFFSET != CONFIG_LINUX_RAM_BASE
          */
         free_area_init_node(0,                  /* node-id */
                             zones_size,         /* num pages per zone */