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From:   Appana Durga Kedareswara rao <appana.durga.rao@xilinx.com>
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        <ebiederm@xmission.com>, <appanad@amd.com>
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        <linux-arm-kernel@lists.infradead.org>, <sam@ravnborg.org>,
        Appana Durga Kedareswara rao <appana.durga.rao@xilinx.com>
Subject: [PATCH 2/3] microblaze: Add custom break vector handler for mb manager
Date:   Mon, 27 Jun 2022 12:10:23 +0530
Message-ID: <20220627064024.771037-3-appana.durga.rao@xilinx.com>
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When the TMR Manager detects a fault Lockstep state it is signaled to the
MicroBlaze processors by asserting a break signal, When Microblaze gets
a break vector from tmr Microblaze it's needed to clear/block the break
bit in the tmr manager before performing recovery.
In order to perform recovery need to perform the following steps.
1) Store all internal MicroBlaze registers in RAM
2) Execute a suspend instruction which asserts the reset signal
3) Restore all registers from RAM and execute an RTBD instruction to
return from the reset handler, to resume execution at the place
where the break occurred.

This API supports getting called from kernel space only.

Signed-off-by: Appana Durga Kedareswara rao <appana.durga.rao@xilinx.com>
---
 arch/microblaze/kernel/asm-offsets.c |   7 +
 arch/microblaze/kernel/entry.S       | 206 ++++++++++++++++++++++++++-
 2 files changed, 212 insertions(+), 1 deletion(-)

diff --git a/arch/microblaze/kernel/asm-offsets.c b/arch/microblaze/kernel/asm-offsets.c
index 47ee409508b1..104c3ac5f30c 100644
--- a/arch/microblaze/kernel/asm-offsets.c
+++ b/arch/microblaze/kernel/asm-offsets.c
@@ -120,5 +120,12 @@ int main(int argc, char *argv[])
 	DEFINE(CC_FSR, offsetof(struct cpu_context, fsr));
 	BLANK();
 
+	/* struct cpuinfo */
+	DEFINE(CI_DCS, offsetof(struct cpuinfo, dcache_size));
+	DEFINE(CI_DCL, offsetof(struct cpuinfo, dcache_line_length));
+	DEFINE(CI_ICS, offsetof(struct cpuinfo, icache_size));
+	DEFINE(CI_ICL, offsetof(struct cpuinfo, icache_line_length));
+	BLANK();
+
 	return 0;
 }
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index b8e1dfe02d58..df367bf94b26 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -30,6 +30,7 @@
 
 #include <linux/errno.h>
 #include <asm/signal.h>
+#include <asm/mmu.h>
 
 #undef DEBUG
 
@@ -287,6 +288,44 @@ syscall_debug_table:
 
 .text
 
+.extern cpuinfo
+
+C_ENTRY(mb_flush_dcache):
+	addik	r1, r1, -PT_SIZE
+	SAVE_REGS
+
+	addik	r3, r0, cpuinfo
+	lwi	r7, r3, CI_DCS
+	lwi	r8, r3, CI_DCL
+	sub	r9, r7, r8
+1:
+	wdc.flush r9, r0
+	bgtid	r9, 1b
+	addk	r9, r9, r8
+
+	RESTORE_REGS
+	addik	r1, r1, PT_SIZE
+	rtsd	r15, 8
+	nop
+
+C_ENTRY(mb_invalidate_icache):
+	addik	r1, r1, -PT_SIZE
+	SAVE_REGS
+
+	addik	r3, r0, cpuinfo
+	lwi	r7, r3, CI_ICS
+	lwi	r8, r3, CI_ICL
+	sub	r9, r7, r8
+1:
+	wic 	r9, r0
+	bgtid	r9, 1b
+	addk	r9, r9, r8
+
+	RESTORE_REGS
+	addik	r1, r1, PT_SIZE
+	rtsd	r15, 8
+	nop
+
 /*
  * User trap.
  *
@@ -753,6 +792,160 @@ IRQ_return: /* MS: Make global symbol for debugging */
 	rtid	r14, 0
 	nop
 
+#ifdef CONFIG_MB_MANAGER
+
+#define	PT_PID		PT_SIZE
+#define	PT_TLBI		PT_SIZE + 4
+#define	PT_ZPR		PT_SIZE	+ 8
+#define	PT_TLBL0	PT_SIZE + 12
+#define	PT_TLBH0	PT_SIZE + 16
+
+C_ENTRY(_xtmr_manager_reset):
+	lwi	r1, r0, xmb_manager_stackpointer
+
+	/* Restore MSR */
+	lwi	r2, r1, PT_MSR
+	mts	rmsr, r2
+	bri	4
+
+	/* restore Special purpose registers */
+	lwi	r2, r1, PT_PID
+	mts	rpid, r2
+
+	lwi	r2, r1, PT_TLBI
+	mts	rtlbx, r2
+
+	lwi	r2, r1, PT_ZPR
+	mts	rzpr, r2
+
+#if CONFIG_XILINX_MICROBLAZE0_USE_FPU
+	lwi	r2, r1, PT_FSR
+	mts	rfsr, r2
+#endif
+
+	/* restore all the tlb's */
+	addik	r3, r0, TOPHYS(tlb_skip)
+	addik	r6, r0, PT_TLBL0
+	addik	r7, r0, PT_TLBH0
+restore_tlb:
+	add	r6, r6, r1
+	add	r7, r7, r1
+	lwi	r2, r6, 0
+	mts 	rtlblo, r2
+	lwi	r2, r7, 0
+	mts	rtlbhi, r2
+	addik	r6, r6, 4
+	addik	r7, r7, 4
+	bgtid	r3, restore_tlb
+	addik	r3, r3, -1
+
+	lwi  	r5, r0, TOPHYS(xmb_manager_dev)
+	lwi	r8, r0, TOPHYS(xmb_manager_reset_callback)
+	set_vms
+	/* return from reset need -8 to adjust for rtsd r15, 8 */
+	addik   r15, r0, ret_from_reset - 8
+	rtbd	r8, 0
+	nop
+
+ret_from_reset:
+	set_bip /* Ints masked for state restore */
+	VM_OFF
+	/* MS: Restore all regs */
+	RESTORE_REGS
+	lwi	r14, r1, PT_R14
+	lwi	r16, r1, PT_PC
+	addik	r1, r1, PT_SIZE + 36
+	rtbd	r16, 0
+	nop
+
+/*
+ * Break handler for MB Manager. Enter to _xmb_manager_break by
+ * injecting fault in one of the TMR Microblaze core.
+ * FIXME: This break handler supports getting
+ * called from kernel space only.
+ */
+C_ENTRY(_xmb_manager_break):
+	/*
+	 * Reserve memory in the stack for context store/restore
+	 * (which includes memory for storing tlbs (max two tlbs))
+	 */
+	addik	r1, r1, -PT_SIZE - 36
+	swi	r1, r0, xmb_manager_stackpointer
+	SAVE_REGS
+	swi	r14, r1, PT_R14	/* rewrite saved R14 value */
+	swi	r16, r1, PT_PC; /* PC and r16 are the same */
+
+	lwi	r6, r0, TOPHYS(xmb_manager_baseaddr)
+	lwi	r7, r0, TOPHYS(xmb_manager_crval)
+	/*
+	 * When the break vector gets asserted because of error injection,
+	 * the break signal must be blocked before exiting from the
+	 * break handler, below code configures the tmr manager
+	 * control register to block break signal.
+	 */
+	swi	r7, r6, 0
+
+	/* Save the special purpose registers  */
+	mfs	r2, rpid
+	swi	r2, r1, PT_PID
+
+	mfs	r2, rtlbx
+	swi	r2, r1, PT_TLBI
+
+	mfs	r2, rzpr
+	swi	r2, r1, PT_ZPR
+
+#if CONFIG_XILINX_MICROBLAZE0_USE_FPU
+	mfs	r2, rfsr
+	swi	r2, r1, PT_FSR
+#endif
+	mfs	r2, rmsr
+	swi	r2, r1, PT_MSR
+
+	/* Save all the tlb's */
+	addik	r3, r0, TOPHYS(tlb_skip)
+	addik	r6, r0, PT_TLBL0
+	addik	r7, r0, PT_TLBH0
+save_tlb:
+	add	r6, r6, r1
+	add	r7, r7, r1
+	mfs	r2, rtlblo
+	swi	r2, r6, 0
+	mfs	r2, rtlbhi
+	swi	r2, r7, 0
+	addik	r6, r6, 4
+	addik	r7, r7, 4
+	bgtid	r3, save_tlb
+	addik	r3, r3, -1
+
+	lwi  	r5, r0, TOPHYS(xmb_manager_dev)
+	lwi	r8, r0, TOPHYS(xmb_manager_callback)
+	/* return from break need -8 to adjust for rtsd r15, 8 */
+	addik   r15, r0, ret_from_break - 8
+	rtbd	r8, 0
+	nop
+
+ret_from_break:
+	/* flush the d-cache */
+	bralid	r15, mb_flush_dcache
+	nop
+
+	/*
+	 * To make sure microblaze i-cache is in a proper state
+	 * invalidate the i-cache.
+	 */
+	bralid	r15, mb_invalidate_icache
+	nop
+
+	set_bip; /* Ints masked for state restore */
+	VM_OFF;
+	mbar	1
+	mbar	2
+	bri	4
+	suspend
+	nop
+#endif
+
 /*
  * Debug trap for KGDB. Enter to _debug_exception by brki r16, 0x18
  * and call handling function with saved pt_regs
@@ -964,6 +1157,7 @@ ENTRY(_switch_to)
 .global xmb_manager_crval
 .global xmb_manager_callback
 .global xmb_manager_reset_callback
+.global xmb_manager_stackpointer
 .align 4
 xmb_manager_dev:
 	.long 0
@@ -975,6 +1169,8 @@ xmb_manager_callback:
 	.long 0
 xmb_manager_reset_callback:
 	.long 0
+xmb_manager_stackpointer:
+	.long 0
 
 /*
  * When the break vector gets asserted because of error injection,
@@ -1008,16 +1204,24 @@ ENTRY(_reset)
 	/* These are compiled and loaded into high memory, then
 	 * copied into place in mach_early_setup */
 	.section	.init.ivt, "ax"
-#if CONFIG_MANUAL_RESET_VECTOR
+#if CONFIG_MANUAL_RESET_VECTOR && !defined(CONFIG_MB_MANAGER)
 	.org	0x0
 	brai	CONFIG_MANUAL_RESET_VECTOR
+#elif defined(CONFIG_MB_MANAGER)
+	.org	0x0
+	brai	TOPHYS(_xtmr_manager_reset);
 #endif
 	.org	0x8
 	brai	TOPHYS(_user_exception); /* syscall handler */
 	.org	0x10
 	brai	TOPHYS(_interrupt);	/* Interrupt handler */
+#ifdef CONFIG_MB_MANAGER
+	.org	0x18
+	brai	TOPHYS(_xmb_manager_break);	/* microblaze manager break handler */
+#else
 	.org	0x18
 	brai	TOPHYS(_debug_exception);	/* debug trap handler */
+#endif
 	.org	0x20
 	brai	TOPHYS(_hw_exception_handler);	/* HW exception handler */
 
-- 
2.25.1