EDAC/amd64: Check for memory before fully initializing an instance

Return early before checking for ECC if the node does not have any
populated memory.

Free any cached hardware data before returning. Also, return 0 in this
case since this is not a failure. Other nodes may have memory and the
module should attempt to load an instance for them.

Move printing of hardware information to after the instance is
initialized, so that the information is only printed for nodes with
memory.

Return an error code when ECC is disabled. This check happens after
checking for memory. The module should explicitly fail to load if memory
is populated on a node and ECC is disabled.
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: "linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Robert Richter <rrichter@marvell.com>
Cc: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20191106012448.243970-6-Yazen.Ghannam@amd.com

drivers/edac/amd64_edac.c

@@ -2848,8 +2848,6 @@ static void read_mc_regs(struct amd64_pvt *pvt)
 	edac_dbg(1, "  DIMM type: %s\n", edac_mem_types[pvt->dram_type]);
 
 	determine_ecc_sym_sz(pvt);
-
-	dump_misc_regs(pvt);
 }
 
 /*
@@ -3491,6 +3489,19 @@ static int init_one_instance(struct amd64_pvt *pvt)
 	return 0;
 }
 
+static bool instance_has_memory(struct amd64_pvt *pvt)
+{
+	bool cs_enabled = false;
+	int cs = 0, dct = 0;
+
+	for (dct = 0; dct < fam_type->max_mcs; dct++) {
+		for_each_chip_select(cs, dct, pvt)
+			cs_enabled |= csrow_enabled(cs, dct, pvt);
+	}
+
+	return cs_enabled;
+}
+
 static int probe_one_instance(unsigned int nid)
 {
 	struct pci_dev *F3 = node_to_amd_nb(nid)->misc;
@@ -3520,8 +3531,14 @@ static int probe_one_instance(unsigned int nid)
 	if (ret < 0)
 		goto err_enable;
 
+	ret = 0;
+	if (!instance_has_memory(pvt)) {
+		amd64_info("Node %d: No DIMMs detected.\n", nid);
+		goto err_enable;
+	}
+
 	if (!ecc_enabled(pvt)) {
-		ret = 0;
+		ret = -ENODEV;
 
 		if (!ecc_enable_override)
 			goto err_enable;
@@ -3546,6 +3563,8 @@ static int probe_one_instance(unsigned int nid)
 		goto err_enable;
 	}
 
+	dump_misc_regs(pvt);
+
 	return ret;
 
 err_enable: