[PATCH] powerpc/traps: Recover from L1 instruction cache parity errors on e500v2

[Bastien Curutchet <bastien.curutchet@bootlin.com>]

There is no attempt to recover from an L1 instruction cache parity
error on e500v2 platforms. When this kind of error happens, we fall in
the die_mce() while we could recover from it (cf §3.1 in [1])

Implement a similar recovery than the one implemented on the e500mc
platforms. It consists of invalidating the entire L1 instruction cache
when parity errors are detected.

[1]: https://www.nxp.jp/docs/en/application-note/AN3532.pdf

Signed-off-by: Bastien Curutchet <bastien.curutchet@bootlin.com>
---
Hi all,

There is a real use case behind this: the device I'm working on is a
space product. It encounters this kind of parity errors when it gets
hit by radiations.

To test it, I made a module that triggers the parity errors by a
register of the P2020 that allows to corrupt the cache, you can find
this module here:
https://github.com/bastien-curutchet/linux/tree/b4/icache-parity-error
---
 arch/powerpc/kernel/traps.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 629f2a2d4780..f8a4019153a0 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -724,8 +724,21 @@ int machine_check_e500(struct pt_regs *regs)
 
 	if (reason & MCSR_MCP)
 		pr_cont("Machine Check Signal\n");
-	if (reason & MCSR_ICPERR)
+	if (reason & MCSR_ICPERR) {
 		pr_cont("Instruction Cache Parity Error\n");
+
+		/*
+		 * This is recoverable by invalidating the I-Cache.
+		 * The I-cache flash invalidate clears all lines;
+		 * correct instructions will be re-fetched from memory.
+		 */
+		mtspr(SPRN_L1CSR1, mfspr(SPRN_L1CSR1) | L1CSR1_ICFI);
+		while (mfspr(SPRN_L1CSR1) & L1CSR1_ICFI)
+			;
+
+		return 1;
+	}
+
 	if (reason & MCSR_DCP_PERR)
 		pr_cont("Data Cache Push Parity Error\n");
 	if (reason & MCSR_DCPERR)

---
base-commit: 0fed5eb44e49e79d824edc4ccce012bb57994300
change-id: 20260831-icache-parity-error-b8c6b1ca0a64

Best regards,
-- 
Bastien Curutchet <bastien.curutchet@bootlin.com>