amd64_edac: Simplify ECC override handling

No need for clearing ecc_enable_override and checking it in two places.
Instead, simply check it during probing and act accordingly. Also,
rename the flag bitfields according to the functionality they actually
represent. What is more, make sure original BIOS ECC settings are
restored when the module is unloaded.

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
diff --git a/drivers/edac/amd64_edac.c b/drivers/edac/amd64_edac.c
index 3391e67..dc9caab 100644
--- a/drivers/edac/amd64_edac.c
+++ b/drivers/edac/amd64_edac.c
@@ -2553,14 +2553,14 @@
 
 		if (on) {
 			if (reg->l & K8_MSR_MCGCTL_NBE)
-				pvt->flags.ecc_report = 1;
+				pvt->flags.nb_mce_enable = 1;
 
 			reg->l |= K8_MSR_MCGCTL_NBE;
 		} else {
 			/*
-			 * Turn off ECC reporting only when it was off before
+			 * Turn off NB MCE reporting only when it was off before
 			 */
-			if (!pvt->flags.ecc_report)
+			if (!pvt->flags.nb_mce_enable)
 				reg->l &= ~K8_MSR_MCGCTL_NBE;
 		}
 	}
@@ -2571,22 +2571,11 @@
 	return 0;
 }
 
-/*
- * Only if 'ecc_enable_override' is set AND BIOS had ECC disabled, do "we"
- * enable it.
- */
 static void amd64_enable_ecc_error_reporting(struct mem_ctl_info *mci)
 {
 	struct amd64_pvt *pvt = mci->pvt_info;
 	u32 value, mask = K8_NBCTL_CECCEn | K8_NBCTL_UECCEn;
 
-	if (!ecc_enable_override)
-		return;
-
-	amd64_printk(KERN_WARNING,
-		"'ecc_enable_override' parameter is active, "
-		"Enabling AMD ECC hardware now: CAUTION\n");
-
 	amd64_read_pci_cfg(pvt->misc_f3_ctl, K8_NBCTL, &value);
 
 	/* turn on UECCn and CECCEn bits */
@@ -2611,6 +2600,8 @@
 			"This node reports that DRAM ECC is "
 			"currently Disabled; ENABLING now\n");
 
+		pvt->flags.nb_ecc_prev = 0;
+
 		/* Attempt to turn on DRAM ECC Enable */
 		value |= K8_NBCFG_ECC_ENABLE;
 		pci_write_config_dword(pvt->misc_f3_ctl, K8_NBCFG, value);
@@ -2625,7 +2616,10 @@
 			amd64_printk(KERN_DEBUG,
 				"Hardware accepted DRAM ECC Enable\n");
 		}
+	} else {
+		pvt->flags.nb_ecc_prev = 1;
 	}
+
 	debugf0("NBCFG(2)= 0x%x  CHIPKILL= %s ECC_ENABLE= %s\n", value,
 		(value & K8_NBCFG_CHIPKILL) ? "Enabled" : "Disabled",
 		(value & K8_NBCFG_ECC_ENABLE) ? "Enabled" : "Disabled");
@@ -2644,12 +2638,18 @@
 	value &= ~mask;
 	value |= pvt->old_nbctl;
 
-	/* restore the NB Enable MCGCTL bit */
 	pci_write_config_dword(pvt->misc_f3_ctl, K8_NBCTL, value);
 
+	/* restore previous BIOS DRAM ECC "off" setting which we force-enabled */
+	if (!pvt->flags.nb_ecc_prev) {
+		amd64_read_pci_cfg(pvt->misc_f3_ctl, K8_NBCFG, &value);
+		value &= ~K8_NBCFG_ECC_ENABLE;
+		pci_write_config_dword(pvt->misc_f3_ctl, K8_NBCFG, value);
+	}
+
+	/* restore the NB Enable MCGCTL bit */
 	if (amd64_toggle_ecc_err_reporting(pvt, OFF))
-		amd64_printk(KERN_WARNING, "Error restoring ECC reporting over "
-					   "MCGCTL!\n");
+		amd64_printk(KERN_WARNING, "Error restoring NB MCGCTL settings!\n");
 }
 
 /*
@@ -2690,8 +2690,9 @@
 		if (!ecc_enable_override) {
 			amd64_printk(KERN_NOTICE, "%s", ecc_msg);
 			return -ENODEV;
+		} else {
+			amd64_printk(KERN_WARNING, "Forcing ECC checking on!\n");
 		}
-		ecc_enable_override = 0;
 	}
 
 	return 0;