powerpc/fadump: add fadump support on powernv

Add basic callback functions for FADump on PowerNV platform.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/156821342072.5656.4346362203141486452.stgit@hbathini.in.ibm.com

arch/powerpc/Kconfig

@@ -569,7 +569,7 @@ config CRASH_DUMP
 
 config FA_DUMP
 	bool "Firmware-assisted dump"
-	depends on PPC64 && PPC_RTAS
+	depends on PPC64 && (PPC_RTAS || PPC_POWERNV)
 	select CRASH_CORE
 	select CRASH_DUMP
 	help
@@ -580,7 +580,8 @@ config FA_DUMP
 	  is meant to be a kdump replacement offering robustness and
 	  speed not possible without system firmware assistance.
 
-	  If unsure, say "N"
+	  If unsure, say "y". Only special kernels like petitboot may
+	  need to say "N" here.
 
 config IRQ_ALL_CPUS
 	bool "Distribute interrupts on all CPUs by default"

arch/powerpc/include/asm/fadump-internal.h

@@ -135,4 +135,11 @@ static inline void
 rtas_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node) { }
 #endif
 
+#ifdef CONFIG_PPC_POWERNV
+extern void opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node);
+#else
+static inline void
+opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node) { }
+#endif
+
 #endif /* _ASM_POWERPC_FADUMP_INTERNAL_H */

arch/powerpc/kernel/fadump.c

@@ -107,13 +107,22 @@ static int __init fadump_cma_init(void) { return 1; }
 int __init early_init_dt_scan_fw_dump(unsigned long node, const char *uname,
 				      int depth, void *data)
 {
-	if (depth != 1 || strcmp(uname, "rtas") != 0)
+	if (depth != 1)
 		return 0;
 
+	if (strcmp(uname, "rtas") == 0) {
 		rtas_fadump_dt_scan(&fw_dump, node);
 		return 1;
 	}
 
+	if (strcmp(uname, "ibm,opal") == 0) {
+		opal_fadump_dt_scan(&fw_dump, node);
+		return 1;
+	}
+
+	return 0;
+}
+
 /*
  * If fadump is registered, check if the memory provided
  * falls within boot memory area and reserved memory area.

arch/powerpc/platforms/powernv/Makefile

@@ -7,6 +7,7 @@ obj-y			+= opal-kmsg.o opal-powercap.o opal-psr.o opal-sensor-groups.o
 obj-y			+= ultravisor.o
 
 obj-$(CONFIG_SMP)	+= smp.o subcore.o subcore-asm.o
+obj-$(CONFIG_FA_DUMP)	+= opal-fadump.o
 obj-$(CONFIG_PCI)	+= pci.o pci-ioda.o npu-dma.o pci-ioda-tce.o
 obj-$(CONFIG_CXL_BASE)	+= pci-cxl.o
 obj-$(CONFIG_EEH)	+= eeh-powernv.o

arch/powerpc/platforms/powernv/opal-fadump.c

@@ -0,0 +1,92 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Firmware-Assisted Dump support on POWER platform (OPAL).
+ *
+ * Copyright 2019, Hari Bathini, IBM Corporation.
+ */
+
+#define pr_fmt(fmt) "opal fadump: " fmt
+
+#include <linux/string.h>
+#include <linux/seq_file.h>
+#include <linux/of_fdt.h>
+#include <linux/libfdt.h>
+
+#include <asm/opal.h>
+#include <asm/fadump-internal.h>
+
+static u64 opal_fadump_init_mem_struct(struct fw_dump *fadump_conf)
+{
+	return fadump_conf->reserve_dump_area_start;
+}
+
+static int opal_fadump_register(struct fw_dump *fadump_conf)
+{
+	return -EIO;
+}
+
+static int opal_fadump_unregister(struct fw_dump *fadump_conf)
+{
+	return -EIO;
+}
+
+static int opal_fadump_invalidate(struct fw_dump *fadump_conf)
+{
+	return -EIO;
+}
+
+static int __init opal_fadump_process(struct fw_dump *fadump_conf)
+{
+	return -EINVAL;
+}
+
+static void opal_fadump_region_show(struct fw_dump *fadump_conf,
+				    struct seq_file *m)
+{
+}
+
+static void opal_fadump_trigger(struct fadump_crash_info_header *fdh,
+				const char *msg)
+{
+	int rc;
+
+	rc = opal_cec_reboot2(OPAL_REBOOT_MPIPL, msg);
+	if (rc == OPAL_UNSUPPORTED) {
+		pr_emerg("Reboot type %d not supported.\n",
+			 OPAL_REBOOT_MPIPL);
+	} else if (rc == OPAL_HARDWARE)
+		pr_emerg("No backend support for MPIPL!\n");
+}
+
+static struct fadump_ops opal_fadump_ops = {
+	.fadump_init_mem_struct		= opal_fadump_init_mem_struct,
+	.fadump_register		= opal_fadump_register,
+	.fadump_unregister		= opal_fadump_unregister,
+	.fadump_invalidate		= opal_fadump_invalidate,
+	.fadump_process			= opal_fadump_process,
+	.fadump_region_show		= opal_fadump_region_show,
+	.fadump_trigger			= opal_fadump_trigger,
+};
+
+void __init opal_fadump_dt_scan(struct fw_dump *fadump_conf, u64 node)
+{
+	unsigned long dn;
+
+	/*
+	 * Check if Firmware-Assisted Dump is supported. if yes, check
+	 * if dump has been initiated on last reboot.
+	 */
+	dn = of_get_flat_dt_subnode_by_name(node, "dump");
+	if (dn == -FDT_ERR_NOTFOUND) {
+		pr_debug("FADump support is missing!\n");
+		return;
+	}
+
+	if (!of_flat_dt_is_compatible(dn, "ibm,opal-dump")) {
+		pr_err("Support missing for this f/w version!\n");
+		return;
+	}
+
+	fadump_conf->ops		= &opal_fadump_ops;
+	fadump_conf->fadump_supported	= 1;
+}