amd64_edac: add memory scrubber interface

Borislav:
- fix/cleanup comments
- fix function return value patterns
- cleanup debug calls
Reviewed-by: NMauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: NDoug Thompson <dougthompson@xmission.com>
Signed-off-by: NBorislav Petkov <borislav.petkov@amd.com>

drivers/edac/amd64_edac.c

+#include "amd64_edac.h"
+
+static struct edac_pci_ctl_info *amd64_ctl_pci;
+
+static int report_gart_errors;
+module_param(report_gart_errors, int, 0644);
+
+/*
+ * Set by command line parameter. If BIOS has enabled the ECC, this override is
+ * cleared to prevent re-enabling the hardware by this driver.
+ */
+static int ecc_enable_override;
+module_param(ecc_enable_override, int, 0644);
+
+/* Lookup table for all possible MC control instances */
+struct amd64_pvt;
+static struct mem_ctl_info *mci_lookup[MAX_NUMNODES];
+static struct amd64_pvt *pvt_lookup[MAX_NUMNODES];
+
+/*
+ * Memory scrubber control interface. For K8, memory scrubbing is handled by
+ * hardware and can involve L2 cache, dcache as well as the main memory. With
+ * F10, this is extended to L3 cache scrubbing on CPU models sporting that
+ * functionality.
+ *
+ * This causes the "units" for the scrubbing speed to vary from 64 byte blocks
+ * (dram) over to cache lines. This is nasty, so we will use bandwidth in
+ * bytes/sec for the setting.
+ *
+ * Currently, we only do dram scrubbing. If the scrubbing is done in software on
+ * other archs, we might not have access to the caches directly.
+ */
+
+/*
+ * scan the scrub rate mapping table for a close or matching bandwidth value to
+ * issue. If requested is too big, then use last maximum value found.
+ */
+static int amd64_search_set_scrub_rate(struct pci_dev *ctl, u32 new_bw,
+				       u32 min_scrubrate)
+{
+	u32 scrubval;
+	int i;
+
+	/*
+	 * map the configured rate (new_bw) to a value specific to the AMD64
+	 * memory controller and apply to register. Search for the first
+	 * bandwidth entry that is greater or equal than the setting requested
+	 * and program that. If at last entry, turn off DRAM scrubbing.
+	 */
+	for (i = 0; i < ARRAY_SIZE(scrubrates); i++) {
+		/*
+		 * skip scrub rates which aren't recommended
+		 * (see F10 BKDG, F3x58)
+		 */
+		if (scrubrates[i].scrubval < min_scrubrate)
+			continue;
+
+		if (scrubrates[i].bandwidth <= new_bw)
+			break;
+
+		/*
+		 * if no suitable bandwidth found, turn off DRAM scrubbing
+		 * entirely by falling back to the last element in the
+		 * scrubrates array.
+		 */
+	}
+
+	scrubval = scrubrates[i].scrubval;
+	if (scrubval)
+		edac_printk(KERN_DEBUG, EDAC_MC,
+			    "Setting scrub rate bandwidth: %u\n",
+			    scrubrates[i].bandwidth);
+	else
+		edac_printk(KERN_DEBUG, EDAC_MC, "Turning scrubbing off.\n");
+
+	pci_write_bits32(ctl, K8_SCRCTRL, scrubval, 0x001F);
+
+	return 0;
+}
+
+static int amd64_set_scrub_rate(struct mem_ctl_info *mci, u32 *bandwidth)
+{
+	struct amd64_pvt *pvt = mci->pvt_info;
+	u32 min_scrubrate = 0x0;
+
+	switch (boot_cpu_data.x86) {
+	case 0xf:
+		min_scrubrate = K8_MIN_SCRUB_RATE_BITS;
+		break;
+	case 0x10:
+		min_scrubrate = F10_MIN_SCRUB_RATE_BITS;
+		break;
+	case 0x11:
+		min_scrubrate = F11_MIN_SCRUB_RATE_BITS;
+		break;
+
+	default:
+		amd64_printk(KERN_ERR, "Unsupported family!\n");
+		break;
+	}
+	return amd64_search_set_scrub_rate(pvt->misc_f3_ctl, *bandwidth,
+			min_scrubrate);
+}
+
+static int amd64_get_scrub_rate(struct mem_ctl_info *mci, u32 *bw)
+{
+	struct amd64_pvt *pvt = mci->pvt_info;
+	u32 scrubval = 0;
+	int status = -1, i, ret = 0;
+
+	ret = pci_read_config_dword(pvt->misc_f3_ctl, K8_SCRCTRL, &scrubval);
+	if (ret)
+		debugf0("Reading K8_SCRCTRL failed\n");
+
+	scrubval = scrubval & 0x001F;
+
+	edac_printk(KERN_DEBUG, EDAC_MC,
+		    "pci-read, sdram scrub control value: %d \n", scrubval);
+
+	for (i = 0; ARRAY_SIZE(scrubrates); i++) {
+		if (scrubrates[i].scrubval == scrubval) {
+			*bw = scrubrates[i].bandwidth;
+			status = 0;
+			break;
+		}
+	}
+
+	return status;
+}
+