parisc: Add Page Deallocation Table (PDT) support

The firmare in most parisc machines maintains a Page Deallocation Table (PDT)
which holds a list of physical memory addresses where hardware detected memory
errors (single bit and double bit errors).

This patch adds the missing PDC firmware calls and the logic to read the PDT
from firmware, report all current PDT entries and exclude the reported bad
memory from being used by Linux.

Signed-off-by: Helge Deller <deller@gmx.de>

1 files changed, 143 insertions, 0 deletions

diff --git a/arch/parisc/kernel/pdt.c b/arch/parisc/kernel/pdt.c
new file mode 100644
index 000000000000..f3a797e670b0
--- /dev/null
+++ b/arch/parisc/kernel/pdt.c
@@ -0,0 +1,143 @@
+/*
+ *    Page Deallocation Table (PDT) support
+ *
+ *    The Page Deallocation Table (PDT) holds a table with pointers to bad
+ *    memory (broken RAM modules) which is maintained by firmware.
+ *
+ *    Copyright 2017 by Helge Deller <deller@gmx.de>
+ *
+ *    TODO:
+ *    - check regularily for new bad memory
+ *    - add userspace interface with procfs or sysfs
+ *    - increase number of PDT entries dynamically
+ */
+
+#include <linux/memblock.h>
+#include <linux/seq_file.h>
+
+#include <asm/pdc.h>
+#include <asm/pdcpat.h>
+#include <asm/sections.h>
+#include <asm/pgtable.h>
+
+enum pdt_access_type {
+	PDT_NONE,
+	PDT_PDC,
+	PDT_PAT_NEW,
+	PDT_PAT_OLD
+};
+
+static enum pdt_access_type pdt_type;
+
+/* global PDT status information */
+static struct pdc_mem_retinfo pdt_status;
+
+#define MAX_PDT_TABLE_SIZE	PAGE_SIZE
+#define MAX_PDT_ENTRIES		(MAX_PDT_TABLE_SIZE / sizeof(unsigned long))
+static unsigned long pdt_entry[MAX_PDT_ENTRIES] __page_aligned_bss;
+
+
+/* report PDT entries via /proc/meminfo */
+void arch_report_meminfo(struct seq_file *m)
+{
+	if (pdt_type == PDT_NONE)
+		return;
+
+	seq_printf(m, "PDT_max_entries: %7lu\n",
+			pdt_status.pdt_size);
+	seq_printf(m, "PDT_cur_entries: %7lu\n",
+			pdt_status.pdt_entries);
+}
+
+/*
+ * pdc_pdt_init()
+ *
+ * Initialize kernel PDT structures, read initial PDT table from firmware,
+ * report all current PDT entries and mark bad memory with memblock_reserve()
+ * to avoid that the kernel will use broken memory areas.
+ *
+ */
+void __init pdc_pdt_init(void)
+{
+	int ret, i;
+	unsigned long entries;
+	struct pdc_mem_read_pdt pdt_read_ret;
+
+	if (is_pdc_pat()) {
+		struct pdc_pat_mem_retinfo pat_rinfo;
+
+		pdt_type = PDT_PAT_NEW;
+		ret = pdc_pat_mem_pdt_info(&pat_rinfo);
+		pdt_status.pdt_size = pat_rinfo.max_pdt_entries;
+		pdt_status.pdt_entries = pat_rinfo.current_pdt_entries;
+		pdt_status.pdt_status = 0;
+		pdt_status.first_dbe_loc = pat_rinfo.first_dbe_loc;
+		pdt_status.good_mem = pat_rinfo.good_mem;
+	} else {
+		pdt_type = PDT_PDC;
+		ret = pdc_mem_pdt_info(&pdt_status);
+	}
+
+	if (ret != PDC_OK) {
+		pdt_type = PDT_NONE;
+		pr_info("PDT: Firmware does not provide any page deallocation"
+			" information.\n");
+		return;
+	}
+
+	entries = pdt_status.pdt_entries;
+	WARN_ON(entries > MAX_PDT_ENTRIES);
+
+	pr_info("PDT: size %lu, entries %lu, status %lu, dbe_loc 0x%lx,"
+		" good_mem %lu\n",
+			pdt_status.pdt_size, pdt_status.pdt_entries,
+			pdt_status.pdt_status, pdt_status.first_dbe_loc,
+			pdt_status.good_mem);
+
+	if (entries == 0) {
+		pr_info("PDT: Firmware reports all memory OK.\n");
+		return;
+	}
+
+	if (pdt_status.first_dbe_loc &&
+		pdt_status.first_dbe_loc <= __pa((unsigned long)&_end))
+		pr_crit("CRITICAL: Bad memory inside kernel image memory area!\n");
+
+	pr_warn("PDT: Firmware reports %lu entries of faulty memory:\n",
+		entries);
+
+	if (pdt_type == PDT_PDC)
+		ret = pdc_mem_pdt_read_entries(&pdt_read_ret, pdt_entry);
+	else {
+#ifdef CONFIG_64BIT
+		struct pdc_pat_mem_read_pd_retinfo pat_pret;
+
+		ret = pdc_pat_mem_read_cell_pdt(&pat_pret, pdt_entry,
+			MAX_PDT_ENTRIES);
+		if (ret != PDC_OK) {
+			pdt_type = PDT_PAT_OLD;
+			ret = pdc_pat_mem_read_pd_pdt(&pat_pret, pdt_entry,
+				MAX_PDT_TABLE_SIZE, 0);
+		}
+#else
+		ret = PDC_BAD_PROC;
+#endif
+	}
+
+	if (ret != PDC_OK) {
+		pdt_type = PDT_NONE;
+		pr_debug("PDT type %d, retval = %d\n", pdt_type, ret);
+		return;
+	}
+
+	for (i = 0; i < pdt_status.pdt_entries; i++) {
+		if (i < 20)
+			pr_warn("PDT: BAD PAGE #%d at 0x%08lx (error_type = %lu)\n",
+				i,
+				pdt_entry[i] & PAGE_MASK,
+				pdt_entry[i] & 1);
+
+		/* mark memory page bad */
+		memblock_reserve(pdt_entry[i] & PAGE_MASK, PAGE_SIZE);
+	}
+}