powerpc/fsl_booke: make sure PAGE_OFFSET map to memstart_addr for relocatable kernel

This is always true for a non-relocatable kernel. Otherwise the kernel
would get stuck. But for a relocatable kernel, it seems a little
complicated. When booting a relocatable kernel, we just align the
kernel start addr to 64M and map the PAGE_OFFSET from there. The
relocation will base on this virtual address. But if this address
is not the same as the memstart_addr, we will have to change the
map of PAGE_OFFSET to the real memstart_addr and do another relocation
again.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
[scottwood@freescale.com: make offset long and non-negative in simple case]
Signed-off-by: Scott Wood <scottwood@freescale.com>

3 files changed, 106 insertions, 12 deletions

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index 75f0223e6d0d..b1f7edc3c360 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -81,6 +81,39 @@ _ENTRY(_start);
         mr      r23,r3
         mr      r25,r4
 
+        bl      0f
+0:      mflr    r8
+        addis   r3,r8,(is_second_reloc - 0b)@ha
+        lwz     r19,(is_second_reloc - 0b)@l(r3)
+
+        /* Check if this is the second relocation. */
+        cmpwi   r19,1
+        bne     1f
+
+        /*
+         * For the second relocation, we already get the real memstart_addr
+         * from device tree. So we will map PAGE_OFFSET to memstart_addr,
+         * then the virtual address of start kernel should be:
+         *          PAGE_OFFSET + (kernstart_addr - memstart_addr)
+         * Since the offset between kernstart_addr and memstart_addr should
+         * never be beyond 1G, so we can just use the lower 32bit of them
+         * for the calculation.
+         */
+        lis     r3,PAGE_OFFSET@h
+
+        addis   r4,r8,(kernstart_addr - 0b)@ha
+        addi    r4,r4,(kernstart_addr - 0b)@l
+        lwz     r5,4(r4)
+
+        addis   r6,r8,(memstart_addr - 0b)@ha
+        addi    r6,r6,(memstart_addr - 0b)@l
+        lwz     r7,4(r6)
+
+        subf    r5,r7,r5
+        add     r3,r3,r5
+        b       2f
+
+1:
         /*
          * We have the runtime (virutal) address of our base.
          * We calculate our shift of offset from a 64M page.
@@ -94,7 +127,14 @@ _ENTRY(_start);
         subf    r3,r5,r6                        /* r3 = r6 - r5 */
         add     r3,r4,r3                        /* Required Virtual Address */
 
-        bl      relocate
+2:      bl      relocate
+
+        /*
+         * For the second relocation, we already set the right tlb entries
+         * for the kernel space, so skip the code in fsl_booke_entry_mapping.S
+        */
+        cmpwi   r19,1
+        beq     set_ivor
 #endif
 
 /* We try to not make any assumptions about how the boot loader
@@ -122,6 +162,7 @@ _ENTRY(__early_start)
 #include "fsl_booke_entry_mapping.S"
 #undef ENTRY_MAPPING_BOOT_SETUP
 
+set_ivor:
         /* Establish the interrupt vector offsets */
         SET_IVOR(0,  CriticalInput);
         SET_IVOR(1,  MachineCheck);
@@ -207,11 +248,13 @@ _ENTRY(__early_start)
         bl      early_init
 
 #ifdef CONFIG_RELOCATABLE
+        mr      r3,r30
+        mr      r4,r31
 #ifdef CONFIG_PHYS_64BIT
-        mr      r3,r23
-        mr      r4,r25
+        mr      r5,r23
+        mr      r6,r25
 #else
-        mr      r3,r25
+        mr      r5,r25
 #endif
         bl      relocate_init
 #endif
@@ -1207,6 +1250,9 @@ _GLOBAL(switch_to_as1)
 /*
  * Restore to the address space 0 and also invalidate the tlb entry created
  * by switch_to_as1.
+ * r3 - the tlb entry which should be invalidated
+ * r4 - __pa(PAGE_OFFSET in AS1) - __pa(PAGE_OFFSET in AS0)
+ * r5 - device tree virtual address. If r4 is 0, r5 is ignored.
 */
 _GLOBAL(restore_to_as0)
         mflr    r0
@@ -1215,7 +1261,15 @@ _GLOBAL(restore_to_as0)
 0:      mflr    r9
         addi    r9,r9,1f - 0b
 
-        mfmsr   r7
+        /*
+         * We may map the PAGE_OFFSET in AS0 to a different physical address,
+         * so we need calculate the right jump and device tree address based
+         * on the offset passed by r4.
+         */
+        add     r9,r9,r4
+        add     r5,r5,r4
+
+2:      mfmsr   r7
         li      r8,(MSR_IS | MSR_DS)
         andc    r7,r7,r8
 
@@ -1234,9 +1288,19 @@ _GLOBAL(restore_to_as0)
         mtspr   SPRN_MAS1,r9
         tlbwe
         isync
+
+        cmpwi   r4,0
+        bne     3f
         mtlr    r0
         blr
 
+        /*
+         * The PAGE_OFFSET will map to a different physical address,
+         * jump to _start to do another relocation again.
+        */
+3:      mr      r3,r5
+        bl      _start
+
 /*
  * We put a few things here that have to be page-aligned. This stuff
  * goes at the beginning of the data segment, which is page-aligned.
diff --git a/arch/powerpc/mm/fsl_booke_mmu.c b/arch/powerpc/mm/fsl_booke_mmu.c
index ca956c83e3a2..95deb9fdf92f 100644
--- a/arch/powerpc/mm/fsl_booke_mmu.c
+++ b/arch/powerpc/mm/fsl_booke_mmu.c
@@ -231,7 +231,7 @@ void __init adjust_total_lowmem(void)
 
         i = switch_to_as1();
         __max_low_memory = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM);
-        restore_to_as0(i);
+        restore_to_as0(i, 0, 0);
 
         pr_info("Memory CAM mapping: ");
         for (i = 0; i < tlbcam_index - 1; i++)
@@ -252,17 +252,25 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
 }
 
 #ifdef CONFIG_RELOCATABLE
-notrace void __init relocate_init(phys_addr_t start)
+int __initdata is_second_reloc;
+notrace void __init relocate_init(u64 dt_ptr, phys_addr_t start)
 {
         unsigned long base = KERNELBASE;
 
+        kernstart_addr = start;
+        if (is_second_reloc) {
+                virt_phys_offset = PAGE_OFFSET - memstart_addr;
+                return;
+        }
+
         /*
          * Relocatable kernel support based on processing of dynamic
-         * relocation entries.
-         * Compute the virt_phys_offset :
+         * relocation entries. Before we get the real memstart_addr,
+         * We will compute the virt_phys_offset like this:
          * virt_phys_offset = stext.run - kernstart_addr
          *
-         * stext.run = (KERNELBASE & ~0x3ffffff) + (kernstart_addr & 0x3ffffff)
+         * stext.run = (KERNELBASE & ~0x3ffffff) +
+         *                              (kernstart_addr & 0x3ffffff)
          * When we relocate, we have :
          *
          *      (kernstart_addr & 0x3ffffff) = (stext.run & 0x3ffffff)
@@ -272,10 +280,32 @@ notrace void __init relocate_init(phys_addr_t start)
          *                              (kernstart_addr & ~0x3ffffff)
          *
          */
-        kernstart_addr = start;
         start &= ~0x3ffffff;
         base &= ~0x3ffffff;
         virt_phys_offset = base - start;
+        early_get_first_memblock_info(__va(dt_ptr), NULL);
+        /*
+         * We now get the memstart_addr, then we should check if this
+         * address is the same as what the PAGE_OFFSET map to now. If
+         * not we have to change the map of PAGE_OFFSET to memstart_addr
+         * and do a second relocation.
+         */
+        if (start != memstart_addr) {
+                int n;
+                long offset = start - memstart_addr;
+
+                is_second_reloc = 1;
+                n = switch_to_as1();
+                /* map a 64M area for the second relocation */
+                if (memstart_addr > start)
+                        map_mem_in_cams(0x4000000, CONFIG_LOWMEM_CAM_NUM);
+                else
+                        map_mem_in_cams_addr(start, PAGE_OFFSET + offset,
+                                        0x4000000, CONFIG_LOWMEM_CAM_NUM);
+                restore_to_as0(n, offset, __va(dt_ptr));
+                /* We should never reach here */
+                panic("Relocation error");
+        }
 }
 #endif
 #endif
diff --git a/arch/powerpc/mm/mmu_decl.h b/arch/powerpc/mm/mmu_decl.h
index eefbf7bb4331..91da910210cb 100644
--- a/arch/powerpc/mm/mmu_decl.h
+++ b/arch/powerpc/mm/mmu_decl.h
@@ -149,7 +149,7 @@ extern void MMU_init_hw(void);
 extern unsigned long mmu_mapin_ram(unsigned long top);
 extern void adjust_total_lowmem(void);
 extern int switch_to_as1(void);
-extern void restore_to_as0(int esel);
+extern void restore_to_as0(int esel, int offset, void *dt_ptr);
 #endif
 extern void loadcam_entry(unsigned int index);