[POWERPC] 4xx: Fix TLB 0 problem with CONFIG_SERIAL_TEXT_DEBUG

Right now TLB entry 0 ist used as UART0 mapping for the early debug
output (via CONFIG_SERIAL_TEXT_DEBUG). This causes problems when many
TLB's get used upon Linux bootup (e.g. while PCIe scanning behind
bridges and/or switches on 440SPe platforms). This will overwrite the
TLB 0 entry and further debug output's may crash/hang the system.

This patch moves the early debug UART0 TLB entry from 0 to 62 as done
in arch/powerpc. This way it is in the "pinned" area and will not get
overwritten. Also the arch/ppc/mm/44x_mmu.c code is now synced with the
newer code from arch/powerpc.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>

2 files changed, 17 insertions, 36 deletions

diff --git a/arch/ppc/kernel/head_44x.S b/arch/ppc/kernel/head_44x.S
index 75bbc937ed73..ebb5a403829f 100644
--- a/arch/ppc/kernel/head_44x.S
+++ b/arch/ppc/kernel/head_44x.S
@@ -195,7 +195,7 @@ skpinv:	addi	r4,r4,1				/* Increment */
         li      r5,0
         ori     r5,r5,(PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_I | PPC44x_TLB_G)
 
-        li      r0,0                    /* TLB slot 0 */
+        li      r0,62                   /* TLB slot 62 */
 
         tlbwe   r3,r0,PPC44x_TLB_PAGEID /* Load the pageid fields */
         tlbwe   r4,r0,PPC44x_TLB_XLAT   /* Load the translation fields */
diff --git a/arch/ppc/mm/44x_mmu.c b/arch/ppc/mm/44x_mmu.c
index 6536a25cfcb8..fbb577a0d165 100644
--- a/arch/ppc/mm/44x_mmu.c
+++ b/arch/ppc/mm/44x_mmu.c
@@ -60,38 +60,28 @@ extern char etext[], _stext[];
  * Just needed it declared someplace.
  */
 unsigned int tlb_44x_index = 0;
-unsigned int tlb_44x_hwater = 62;
+unsigned int tlb_44x_hwater = PPC4XX_TLB_SIZE - 1 - PPC44x_EARLY_TLBS;
 int icache_44x_need_flush;
 
 /*
  * "Pins" a 256MB TLB entry in AS0 for kernel lowmem
  */
-static void __init
-ppc44x_pin_tlb(int slot, unsigned int virt, unsigned int phys)
+static void __init ppc44x_pin_tlb(unsigned int virt, unsigned int phys)
 {
-        unsigned long attrib = 0;
-
-        __asm__ __volatile__("\
-        clrrwi  %2,%2,10\n\
-        ori     %2,%2,%4\n\
-        clrrwi  %1,%1,10\n\
-        li      %0,0\n\
-        ori     %0,%0,%5\n\
-        tlbwe   %2,%3,%6\n\
-        tlbwe   %1,%3,%7\n\
-        tlbwe   %0,%3,%8"
+        __asm__ __volatile__(
+                "tlbwe  %2,%3,%4\n"
+                "tlbwe  %1,%3,%5\n"
+                "tlbwe  %0,%3,%6\n"
         :
-        : "r" (attrib), "r" (phys), "r" (virt), "r" (slot),
-          "i" (PPC44x_TLB_VALID | PPC44x_TLB_256M),
-          "i" (PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_SX | PPC44x_TLB_G),
+        : "r" (PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_SX | PPC44x_TLB_G),
+          "r" (phys),
+          "r" (virt | PPC44x_TLB_VALID | PPC44x_TLB_256M),
+          "r" (tlb_44x_hwater--), /* slot for this TLB entry */
           "i" (PPC44x_TLB_PAGEID),
           "i" (PPC44x_TLB_XLAT),
           "i" (PPC44x_TLB_ATTRIB));
 }
 
-/*
- * MMU_init_hw does the chip-specific initialization of the MMU hardware.
- */
 void __init MMU_init_hw(void)
 {
         flush_instruction_cache();
@@ -99,22 +89,13 @@ void __init MMU_init_hw(void)
 
 unsigned long __init mmu_mapin_ram(void)
 {
-        unsigned int pinned_tlbs = 1;
-        int i;
-
-        /* Determine number of entries necessary to cover lowmem */
-        pinned_tlbs = (unsigned int)
-                (_ALIGN(total_lowmem, PPC_PIN_SIZE) >> PPC44x_PIN_SHIFT);
-
-        /* Write upper watermark to save location */
-        tlb_44x_hwater = PPC44x_LOW_SLOT - pinned_tlbs;
+        unsigned long addr;
 
-        /* If necessary, set additional pinned TLBs */
-        if (pinned_tlbs > 1)
-                for (i = (PPC44x_LOW_SLOT-(pinned_tlbs-1)); i < PPC44x_LOW_SLOT; i++) {
-                        unsigned int phys_addr = (PPC44x_LOW_SLOT-i) * PPC_PIN_SIZE;
-                        ppc44x_pin_tlb(i, phys_addr+PAGE_OFFSET, phys_addr);
-                }
+        /* Pin in enough TLBs to cover any lowmem not covered by the
+         * initial 256M mapping established in head_44x.S */
+        for (addr = PPC_PIN_SIZE; addr < total_lowmem;
+             addr += PPC_PIN_SIZE)
+                ppc44x_pin_tlb(addr + PAGE_OFFSET, addr);
 
         return total_lowmem;
 }