[PATCH v3 6/7] powerpc/8xx: Rework CONFIG_PIN_TLB handling
From: Christophe Leroy
Date: Tue May 17 2016 - 03:03:56 EST
On recent kernels, with some debug options like for instance
CONFIG_LOCKDEP, the BSS requires more than 8M memory, allthough
the kernel code fits in the first 8M.
Today, it is necessary to activate CONFIG_PIN_TLB to get more than 8M
at startup, allthough pinning TLB is not necessary for that.
We could have inconditionaly mapped 16 or 24M bytes at startup
but some old hardware only have 8M and mapping non-existing RAM
would be an issue due to speculative accesses.
With the preceding patch however, the TLB entries are populated on
demand. By setting up the TLB miss handler to handle up to 24M until
the handler is patched for the entire memory space, it is possible
to allow access up to more memory without mapping non-existing RAM.
It is therefore not needed anymore to map memory data at all
at startup. It will be handled by the TLB miss handler.
One might still want to PIN the IMMR and the first 24M of RAM.
It is now possible to do it in the C memory initialisation
functions. In addition, we now know how much memory we have
when we do it, so we are able to adapt the pining to the
real amount of memory available. So boards with less than 24M
can now also benefit from PIN_TLB.
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
---
v2: Fixed a test
v3: No change
arch/powerpc/kernel/head_8xx.S | 44 ++++--------------------------------------
arch/powerpc/mm/8xx_mmu.c | 27 ++++++++++++++++++--------
2 files changed, 23 insertions(+), 48 deletions(-)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 3de7d02..00cc9df 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -491,7 +491,7 @@ _ENTRY(DTLBMiss_jmp)
4:
_ENTRY(DTLBMiss_cmp)
- cmpli cr0, r11, PAGE_OFFSET@h
+ cmpli cr0, r11, (PAGE_OFFSET + 0x1800000)@h
lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha
bge- 3b
@@ -586,7 +586,7 @@ FixupDAR:/* Entry point for dcbx workaround. */
BRANCH_UNLESS_KERNEL(3f)
rlwinm r11, r10, 16, 0xfff8
_ENTRY(FixupDAR_cmp)
- cmpli cr7, r11, PAGE_OFFSET@h
+ cmpli cr7, r11, (PAGE_OFFSET + 0x1800000)@h
blt- cr7, 200f
lis r11, (swapper_pg_dir-PAGE_OFFSET)@ha
/* Insert level 1 index */
@@ -823,23 +823,16 @@ initial_mmu:
mtspr SPRN_MD_CTR, r10 /* Set data TLB control */
#endif
- /* Now map the lower 8 Meg into the TLBs. For this quick hack,
- * we can load the instruction and data TLB registers with the
- * same values.
- */
+ /* Now map the lower 8 Meg into the ITLB. */
lis r8, KERNELBASE@h /* Create vaddr for TLB */
ori r8, r8, MI_EVALID /* Mark it valid */
mtspr SPRN_MI_EPN, r8
- mtspr SPRN_MD_EPN, r8
li r8, MI_PS8MEG | (2 << 5) /* Set 8M byte page, APG 2 */
ori r8, r8, MI_SVALID /* Make it valid */
mtspr SPRN_MI_TWC, r8
- li r8, MI_PS8MEG /* Set 8M byte page, APG 0 */
- ori r8, r8, MI_SVALID /* Make it valid */
- mtspr SPRN_MD_TWC, r8
li r8, MI_BOOTINIT /* Create RPN for address 0 */
mtspr SPRN_MI_RPN, r8 /* Store TLB entry */
- mtspr SPRN_MD_RPN, r8
+
lis r8, MI_APG_INIT@h /* Set protection modes */
ori r8, r8, MI_APG_INIT@l
mtspr SPRN_MI_AP, r8
@@ -851,9 +844,6 @@ initial_mmu:
* internal registers (among other things).
*/
#ifdef CONFIG_PIN_TLB
- addi r10, r10, 0x0100
- mtspr SPRN_MD_CTR, r10
-#endif
mfspr r9, 638 /* Get current IMMR */
andis. r9, r9, 0xfff8 /* Get 512 kbytes boundary */
@@ -866,32 +856,6 @@ initial_mmu:
mr r8, r9 /* Create paddr for TLB */
ori r8, r8, MI_BOOTINIT|0x2 /* Inhibit cache -- Cort */
mtspr SPRN_MD_RPN, r8
-
-#ifdef CONFIG_PIN_TLB
- /* Map two more 8M kernel data pages.
- */
- addi r10, r10, 0x0100
- mtspr SPRN_MD_CTR, r10
-
- lis r8, KERNELBASE@h /* Create vaddr for TLB */
- addis r8, r8, 0x0080 /* Add 8M */
- ori r8, r8, MI_EVALID /* Mark it valid */
- mtspr SPRN_MD_EPN, r8
- li r9, MI_PS8MEG /* Set 8M byte page */
- ori r9, r9, MI_SVALID /* Make it valid */
- mtspr SPRN_MD_TWC, r9
- li r11, MI_BOOTINIT /* Create RPN for address 0 */
- addis r11, r11, 0x0080 /* Add 8M */
- mtspr SPRN_MD_RPN, r11
-
- addi r10, r10, 0x0100
- mtspr SPRN_MD_CTR, r10
-
- addis r8, r8, 0x0080 /* Add 8M */
- mtspr SPRN_MD_EPN, r8
- mtspr SPRN_MD_TWC, r9
- addis r11, r11, 0x0080 /* Add 8M */
- mtspr SPRN_MD_RPN, r11
#endif
/* Since the cache is enabled according to the information we
diff --git a/arch/powerpc/mm/8xx_mmu.c b/arch/powerpc/mm/8xx_mmu.c
index 996dfaa..0f0a83e 100644
--- a/arch/powerpc/mm/8xx_mmu.c
+++ b/arch/powerpc/mm/8xx_mmu.c
@@ -50,16 +50,32 @@ unsigned long p_block_mapped(phys_addr_t pa)
return 0;
}
+#define LARGE_PAGE_SIZE_8M (1<<23)
+
/*
* MMU_init_hw does the chip-specific initialization of the MMU hardware.
*/
void __init MMU_init_hw(void)
{
- /* Nothing to do for the time being but keep it similar to other PPC */
+ /* PIN up to the 3 first 8Mb after IMMR in DTLB table */
+#ifdef CONFIG_PIN_TLB
+ unsigned long ctr = mfspr(SPRN_MD_CTR) & 0xfe000000;
+ unsigned long flags = 0xf0 | MD_SPS16K | _PAGE_SHARED | _PAGE_DIRTY;
+ int i;
+ unsigned long addr = 0;
+ unsigned long mem = total_lowmem;
+
+ for (i = 29; i < 32 && mem >= LARGE_PAGE_SIZE_8M; i++) {
+ mtspr(SPRN_MD_CTR, ctr | (i << 8));
+ mtspr(SPRN_MD_EPN, (unsigned long)__va(addr) | MD_EVALID);
+ mtspr(SPRN_MD_TWC, MD_PS8MEG | MD_SVALID);
+ mtspr(SPRN_MD_RPN, addr | flags | _PAGE_PRESENT);
+ addr += LARGE_PAGE_SIZE_8M;
+ mem -= LARGE_PAGE_SIZE_8M;
+ }
+#endif
}
-#define LARGE_PAGE_SIZE_8M (1<<23)
-
static void mmu_mapin_immr(void)
{
unsigned long p = PHYS_IMMR_BASE;
@@ -124,13 +140,8 @@ void setup_initial_memory_limit(phys_addr_t first_memblock_base,
*/
BUG_ON(first_memblock_base != 0);
-#ifdef CONFIG_PIN_TLB
/* 8xx can only access 24MB at the moment */
memblock_set_current_limit(min_t(u64, first_memblock_size, 0x01800000));
-#else
- /* 8xx can only access 8MB at the moment */
- memblock_set_current_limit(min_t(u64, first_memblock_size, 0x00800000));
-#endif
}
/*
--
2.1.0