microblaze: Improve TLB calculation for small systems

Systems with small amount of memory need to be handled
differently. Linux can't allocate the whole 32MB with two TLBs
because then there is no MMU protection.

Signed-off-by: Michal Simek <monstr@monstr.eu>

6 files changed, 120 insertions, 11 deletions

diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 86ae27871f41..d64c10093b40 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -259,6 +259,10 @@ config MICROBLAZE_32K_PAGES
 
 endchoice
 
+config KERNEL_PAD
+        hex "Kernel PAD for unpacking" if ADVANCED_OPTIONS
+        default "0x80000" if MMU
+
 endmenu
 
 source "mm/Kconfig"
diff --git a/arch/microblaze/include/asm/setup.h b/arch/microblaze/include/asm/setup.h
index 6c72ed7eba98..9f195c094731 100644
--- a/arch/microblaze/include/asm/setup.h
+++ b/arch/microblaze/include/asm/setup.h
@@ -39,7 +39,8 @@ extern void of_platform_reset_gpio_probe(void);
 void time_init(void);
 void init_IRQ(void);
 void machine_early_init(const char *cmdline, unsigned int ram,
-                        unsigned int fdt, unsigned int msr);
+                unsigned int fdt, unsigned int msr, unsigned int tlb0,
+                unsigned int tlb1);
 
 void machine_restart(char *cmd);
 void machine_shutdown(void);
diff --git a/arch/microblaze/include/asm/system.h b/arch/microblaze/include/asm/system.h
index 5a433cbaafb3..01228d2b1351 100644
--- a/arch/microblaze/include/asm/system.h
+++ b/arch/microblaze/include/asm/system.h
@@ -83,6 +83,7 @@ void default_idle(void);
 void free_init_pages(char *what, unsigned long begin, unsigned long end);
 void free_initmem(void);
 extern char *klimit;
+extern unsigned long kernel_tlb;
 extern void ret_from_fork(void);
 
 extern void *alloc_maybe_bootmem(size_t size, gfp_t mask);
diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S
index 441dad80558c..49dd48f9e6ec 100644
--- a/arch/microblaze/kernel/head.S
+++ b/arch/microblaze/kernel/head.S
@@ -168,6 +168,53 @@ _invalidate:
         addik   r3,r0, CONFIG_KERNEL_START /* Load the kernel virtual address */
         tophys(r4,r3)                   /* Load the kernel physical address */
 
+        /* start to do TLB calculation */
+        addik   r12, r0, _end
+        rsub    r12, r3, r12
+        addik   r12, r12, CONFIG_KERNEL_PAD /* that's the pad */
+
+        or r9, r0, r0 /* TLB0 = 0 */
+        or r10, r0, r0 /* TLB1 = 0 */
+
+        addik   r11, r12, -0x1000000
+        bgei    r11, GT16 /* size is greater than 16MB */
+        addik   r11, r12, -0x0800000
+        bgei    r11, GT8 /* size is greater than 8MB */
+        addik   r11, r12, -0x0400000
+        bgei    r11, GT4 /* size is greater than 4MB */
+        /* size is less than 4MB */
+        addik   r11, r12, -0x0200000
+        bgei    r11, GT2 /* size is greater than 2MB */
+        addik   r9, r0, 0x0100000 /* TLB0 must be 1MB */
+        addik   r11, r12, -0x0100000
+        bgei    r11, GT1 /* size is greater than 1MB */
+        /* TLB1 is 0 which is setup above */
+        bri tlb_end
+GT4: /* r11 contains the rest - will be either 1 or 4 */
+        ori r9, r0, 0x400000 /* TLB0 is 4MB */
+        bri TLB1
+GT16: /* TLB0 is 16MB */
+        addik   r9, r0, 0x1000000 /* means TLB0 is 16MB */
+TLB1:
+        /* must be used r2 because of substract if failed */
+        addik   r2, r11, -0x0400000
+        bgei    r2, GT20 /* size is greater than 16MB */
+        /* size is >16MB and <20MB */
+        addik   r11, r11, -0x0100000
+        bgei    r11, GT17 /* size is greater than 17MB */
+        /* kernel is >16MB and < 17MB */
+GT1:
+        addik   r10, r0, 0x0100000 /* means TLB1 is 1MB */
+        bri tlb_end
+GT2: /* TLB0 is 0 and TLB1 will be 4MB */
+GT17: /* TLB1 is 4MB - kernel size <20MB */
+        addik   r10, r0, 0x0400000 /* means TLB1 is 4MB */
+        bri tlb_end
+GT8: /* TLB0 is still zero that's why I can use only TLB1 */
+GT20: /* TLB1 is 16MB - kernel size >20MB */
+        addik   r10, r0, 0x1000000 /* means TLB1 is 16MB */
+tlb_end:
+
         /*
          * Configure and load two entries into TLB slots 0 and 1.
          * In case we are pinning TLBs, these are reserved in by the
@@ -177,16 +224,56 @@ _invalidate:
         andi    r4,r4,0xfffffc00        /* Mask off the real page number */
         ori     r4,r4,(TLB_WR | TLB_EX) /* Set the write and execute bits */
 
+        /* TLB0 can be zeroes that's why we not setup it */
+        beqi    r9, jump_over
+
+        /* look at the code below */
+        ori     r30, r0, 0x200
+        andi    r29, r9, 0x100000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+        andi    r29, r9, 0x400000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+        andi    r29, r9, 0x1000000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+1:
+        ori r11, r30, 0
+
         andi    r3,r3,0xfffffc00        /* Mask off the effective page number */
-        ori     r3,r3,(TLB_VALID | TLB_PAGESZ(PAGESZ_16M))
+        ori     r3,r3,(TLB_VALID)
+        or      r3, r3, r11
 
         mts     rtlbx,r0                /* TLB slow 0 */
 
         mts     rtlblo,r4               /* Load the data portion of the entry */
         mts     rtlbhi,r3               /* Load the tag portion of the entry */
 
-        addik   r4, r4, 0x01000000      /* Map next 16 M entries */
-        addik   r3, r3, 0x01000000
+jump_over:
+        /* TLB1 can be zeroes that's why we not setup it */
+        beqi    r10, jump_over2
+
+        /* look at the code below */
+        ori     r30, r0, 0x200
+        andi    r29, r10, 0x100000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+        andi    r29, r10, 0x400000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+        andi    r29, r10, 0x1000000
+        bneid   r29, 1f
+        addik   r30, r30, 0x80
+1:
+        ori r12, r30, 0
+
+        addk    r4, r4, r9      /* previous addr + TLB0 size */
+        addk    r3, r3, r9
+
+        andi    r3,r3,0xfffffc00        /* Mask off the effective page number */
+        ori     r3,r3,(TLB_VALID)
+        or      r3, r3, r12
 
         ori     r6,r0,1                 /* TLB slot 1 */
         mts     rtlbx,r6
@@ -194,6 +281,7 @@ _invalidate:
         mts     rtlblo,r4               /* Load the data portion of the entry */
         mts     rtlbhi,r3               /* Load the tag portion of the entry */
 
+jump_over2:
         /*
          * Load a TLB entry for LMB, since we need access to
          * the exception vectors, using a 4k real==virtual mapping.
@@ -237,8 +325,8 @@ start_here:
          * Please see $(ARCH)/mach-$(SUBARCH)/setup.c for
          * the function.
          */
-        addik   r9, r0, machine_early_init
-        brald   r15, r9
+        addik   r11, r0, machine_early_init
+        brald   r15, r11
         nop
 
 #ifndef CONFIG_MMU
diff --git a/arch/microblaze/kernel/setup.c b/arch/microblaze/kernel/setup.c
index 604cd9dd1333..a1fa2a5813bf 100644
--- a/arch/microblaze/kernel/setup.c
+++ b/arch/microblaze/kernel/setup.c
@@ -97,8 +97,11 @@ inline unsigned get_romfs_len(unsigned *addr)
 }
 #endif  /* CONFIG_MTD_UCLINUX_EBSS */
 
+unsigned long kernel_tlb;
+
 void __init machine_early_init(const char *cmdline, unsigned int ram,
-                unsigned int fdt, unsigned int msr)
+                unsigned int fdt, unsigned int msr, unsigned int tlb0,
+                unsigned int tlb1)
 {
         unsigned long *src, *dst;
         unsigned int offset = 0;
@@ -145,6 +148,12 @@ void __init machine_early_init(const char *cmdline, unsigned int ram,
         setup_early_printk(NULL);
 #endif
 
+        /* setup kernel_tlb after BSS cleaning
+         * Maybe worth to move to asm code */
+        kernel_tlb = tlb0 + tlb1;
+        /* printk("TLB1 0x%08x, TLB0 0x%08x, tlb 0x%x\n", tlb0,
+                                                        tlb1, kernel_tlb); */
+
         printk("Ramdisk addr 0x%08x, ", ram);
         if (fdt)
                 printk("FDT at 0x%08x\n", fdt);
diff --git a/arch/microblaze/mm/init.c b/arch/microblaze/mm/init.c
index 95297b13dd9e..ce80823051ba 100644
--- a/arch/microblaze/mm/init.c
+++ b/arch/microblaze/mm/init.c
@@ -398,10 +398,16 @@ asmlinkage void __init mmu_init(void)
                 machine_restart(NULL);
         }
 
-        if ((u32) memblock.memory.regions[0].size < 0x1000000) {
-                printk(KERN_EMERG "Memory must be greater than 16MB\n");
+        if ((u32) memblock.memory.regions[0].size < 0x400000) {
+                printk(KERN_EMERG "Memory must be greater than 4MB\n");
                 machine_restart(NULL);
         }
+
+        if ((u32) memblock.memory.regions[0].size < kernel_tlb) {
+                printk(KERN_EMERG "Kernel size is greater than memory node\n");
+                machine_restart(NULL);
+        }
+
         /* Find main memory where the kernel is */
         memory_start = (u32) memblock.memory.regions[0].base;
         lowmem_size = memory_size = (u32) memblock.memory.regions[0].size;
@@ -462,11 +468,11 @@ void __init *early_get_page(void)
                 p = alloc_bootmem_pages(PAGE_SIZE);
         } else {
                 /*
-                 * Mem start + 32MB -> here is limit
+                 * Mem start + kernel_tlb -> here is limit
                  * because of mem mapping from head.S
                  */
                 p = __va(memblock_alloc_base(PAGE_SIZE, PAGE_SIZE,
-                                        memory_start + 0x2000000));
+                                        memory_start + kernel_tlb));
         }
         return p;
 }