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>
diff --git a/arch/microblaze/kernel/head.S b/arch/microblaze/kernel/head.S
index 441dad8..49dd48f 100644
--- a/arch/microblaze/kernel/head.S
+++ b/arch/microblaze/kernel/head.S
@@ -168,6 +168,53 @@
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 @@
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 @@
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 @@
* 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