powerpc/8xx: Don't set IMMR map anymore at boot

Only early debug requires IMMR to be mapped early.

No need to set it up and pin it in assembly. Map it
through page tables at udbg init when necessary.

If CONFIG_PIN_TLB_IMMR is selected, pin it once we
don't need the 32 Mb pinned RAM anymore.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/13c1e8539fdf363d3146f4884e5c3c76c6c308b5.1589866984.git.christophe.leroy@csgroup.eu

arch/powerpc/kernel/head_8xx.S

@@ -749,6 +749,23 @@ start_here:
 	rfi
 /* Load up the kernel context */
 2:
+#ifdef CONFIG_PIN_TLB_IMMR
+	lis	r0, MD_TWAM@h
+	oris	r0, r0, 0x1f00
+	mtspr	SPRN_MD_CTR, r0
+	LOAD_REG_IMMEDIATE(r0, VIRT_IMMR_BASE | MD_EVALID)
+	tlbie	r0
+	mtspr	SPRN_MD_EPN, r0
+	LOAD_REG_IMMEDIATE(r0, MD_SVALID | MD_PS512K | MD_GUARDED)
+	mtspr	SPRN_MD_TWC, r0
+	mfspr   r0, SPRN_IMMR
+	rlwinm	r0, r0, 0, 0xfff80000
+	ori	r0, r0, 0xf0 | _PAGE_DIRTY | _PAGE_SPS | _PAGE_SH | \
+			_PAGE_NO_CACHE | _PAGE_PRESENT
+	mtspr	SPRN_MD_RPN, r0
+	lis	r0, (MD_TWAM | MD_RSV4I)@h
+	mtspr	SPRN_MD_CTR, r0
+#endif
 	tlbia			/* Clear all TLB entries */
 	sync			/* wait for tlbia/tlbie to finish */
 
@@ -797,28 +814,6 @@ initial_mmu:
 	ori	r8, r8, MD_APG_INIT@l
 	mtspr	SPRN_MD_AP, r8
 
-	/* Map a 512k page for the IMMR to get the processor
-	 * internal registers (among other things).
-	 */
-#ifdef CONFIG_PIN_TLB_IMMR
-	oris	r10, r10, MD_RSV4I@h
-	ori	r10, r10, 0x1c00
-	mtspr	SPRN_MD_CTR, r10
-
-	mfspr	r9, 638			/* Get current IMMR */
-	andis.	r9, r9, 0xfff8		/* Get 512 kbytes boundary */
-
-	lis	r8, VIRT_IMMR_BASE@h	/* Create vaddr for TLB */
-	ori	r8, r8, MD_EVALID	/* Mark it valid */
-	mtspr	SPRN_MD_EPN, r8
-	li	r8, MD_PS512K | MD_GUARDED	/* Set 512k byte page */
-	ori	r8, r8, MD_SVALID	/* Make it valid */
-	mtspr	SPRN_MD_TWC, r8
-	mr	r8, r9			/* Create paddr for TLB */
-	ori	r8, r8, MI_BOOTINIT|0x2 /* Inhibit cache -- Cort */
-	mtspr	SPRN_MD_RPN, r8
-#endif
-
 	/* Now map the lower RAM (up to 32 Mbytes) into the ITLB. */
 #ifdef CONFIG_PIN_TLB_TEXT
 	lis	r8, MI_RSV4I@h

arch/powerpc/mm/mmu_decl.h

@@ -182,6 +182,10 @@ static inline void mmu_mark_initmem_nx(void) { }
 static inline void mmu_mark_rodata_ro(void) { }
 #endif
 
+#ifdef CONFIG_PPC_8xx
+void __init mmu_mapin_immr(void);
+#endif
+
 #ifdef CONFIG_PPC_DEBUG_WX
 void ptdump_check_wx(void);
 #else

arch/powerpc/mm/nohash/8xx.c

@@ -66,7 +66,7 @@ void __init MMU_init_hw(void)
 	if (IS_ENABLED(CONFIG_PIN_TLB_DATA)) {
 		unsigned long ctr = mfspr(SPRN_MD_CTR) & 0xfe000000;
 		unsigned long flags = 0xf0 | MD_SPS16K | _PAGE_SH | _PAGE_DIRTY;
-		int i = IS_ENABLED(CONFIG_PIN_TLB_IMMR) ? 29 : 28;
+		int i = 28;
 		unsigned long addr = 0;
 		unsigned long mem = total_lowmem;
 
@@ -81,12 +81,19 @@ void __init MMU_init_hw(void)
 	}
 }
 
-static void __init mmu_mapin_immr(void)
+static bool immr_is_mapped __initdata;
+
+void __init mmu_mapin_immr(void)
 {
 	unsigned long p = PHYS_IMMR_BASE;
 	unsigned long v = VIRT_IMMR_BASE;
 	int offset;
 
+	if (immr_is_mapped)
+		return;
+
+	immr_is_mapped = true;
+
 	for (offset = 0; offset < IMMR_SIZE; offset += PAGE_SIZE)
 		map_kernel_page(v + offset, p + offset, PAGE_KERNEL_NCG);
 }
@@ -122,9 +129,10 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 {
 	unsigned long mapped;
 
+	mmu_mapin_immr();
+
 	if (__map_without_ltlbs) {
 		mapped = 0;
-		mmu_mapin_immr();
 		if (!IS_ENABLED(CONFIG_PIN_TLB_IMMR))
 			patch_instruction_site(&patch__dtlbmiss_immr_jmp, ppc_inst(PPC_INST_NOP));
 		if (!IS_ENABLED(CONFIG_PIN_TLB_TEXT))
@@ -143,7 +151,6 @@ unsigned long __init mmu_mapin_ram(unsigned long base, unsigned long top)
 		 */
 		mmu_mapin_ram_chunk(0, einittext8, PAGE_KERNEL_X);
 		mmu_mapin_ram_chunk(einittext8, mapped, PAGE_KERNEL);
-		mmu_mapin_immr();
 	}
 
 	mmu_patch_cmp_limit(&patch__dtlbmiss_linmem_top, mapped);

arch/powerpc/platforms/8xx/Kconfig

@@ -187,7 +187,7 @@ config PIN_TLB_DATA
 
 config PIN_TLB_IMMR
 	bool "Pinned TLB for IMMR"
-	depends on PIN_TLB || PPC_EARLY_DEBUG_CPM
+	depends on PIN_TLB
 	default y
 	help
 	  This pins the IMMR area with a 512kbytes page. In case

arch/powerpc/sysdev/cpm_common.c

@@ -68,6 +68,8 @@ static void udbg_putc_cpm(char c)
 void __init udbg_init_cpm(void)
 {
 #ifdef CONFIG_PPC_8xx
+	mmu_mapin_immr();
+
 	cpm_udbg_txdesc = (u32 __iomem __force *)
 			  (CONFIG_PPC_EARLY_DEBUG_CPM_ADDR - PHYS_IMMR_BASE +
 			   VIRT_IMMR_BASE);