[SCSI] mpt2sas: Provide sysfs attribute to report Backup Rail Monitor Status

A new sysfs shost attribute called "BMR_status" is implemented to
report Backup Rail Monitor status.

This attribute is located in the path
        /sys/class/scsi_host/host#/BMR_status

when reading this adapter attribute, then driver will output the state
of GPIO[24]. It returns "0" if BMR is healthy and it returns "1" for failure.

if it returns an empty string then it means that there was an error while
obtaining the BMR status. Then check dmesg for what error has occured.

Signed-off-by: Sreekanth Reddy <sreekanth.reddy@lsi.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

1 files changed, 70 insertions, 0 deletions

diff --git a/drivers/scsi/mpt2sas/mpt2sas_ctl.c b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
index 6da4a408358c..64254416a178 100644
--- a/drivers/scsi/mpt2sas/mpt2sas_ctl.c
+++ b/drivers/scsi/mpt2sas/mpt2sas_ctl.c
@@ -2690,6 +2690,75 @@ _ctl_ioc_reply_queue_count_show(struct device *cdev,
 static DEVICE_ATTR(reply_queue_count, S_IRUGO,
 	 _ctl_ioc_reply_queue_count_show, NULL);
 
+/**
+ * _ctl_BRM_status_show - Backup Rail Monitor Status
+ * @cdev - pointer to embedded class device
+ * @buf - the buffer returned
+ *
+ * This is number of reply queues
+ *
+ * A sysfs 'read-only' shost attribute.
+ */
+static ssize_t
+_ctl_BRM_status_show(struct device *cdev, struct device_attribute *attr,
+	char *buf)
+{
+	struct Scsi_Host *shost = class_to_shost(cdev);
+	struct MPT2SAS_ADAPTER *ioc = shost_priv(shost);
+	Mpi2IOUnitPage3_t *io_unit_pg3 = NULL;
+	Mpi2ConfigReply_t mpi_reply;
+	u16 backup_rail_monitor_status = 0;
+	u16 ioc_status;
+	int sz;
+	ssize_t rc = 0;
+
+	if (!ioc->is_warpdrive) {
+		printk(MPT2SAS_ERR_FMT "%s: BRM attribute is only for"\
+		    "warpdrive\n", ioc->name, __func__);
+		goto out;
+	}
+
+	/* allocate upto GPIOVal 36 entries */
+	sz = offsetof(Mpi2IOUnitPage3_t, GPIOVal) + (sizeof(u16) * 36);
+	io_unit_pg3 = kzalloc(sz, GFP_KERNEL);
+	if (!io_unit_pg3) {
+		printk(MPT2SAS_ERR_FMT "%s: failed allocating memory"\
+		    "for iounit_pg3: (%d) bytes\n", ioc->name, __func__, sz);
+		goto out;
+	}
+
+	if (mpt2sas_config_get_iounit_pg3(ioc, &mpi_reply, io_unit_pg3, sz) !=
+	    0) {
+		printk(MPT2SAS_ERR_FMT
+		    "%s: failed reading iounit_pg3\n", ioc->name,
+		    __func__);
+		goto out;
+	}
+
+	ioc_status = le16_to_cpu(mpi_reply.IOCStatus) & MPI2_IOCSTATUS_MASK;
+	if (ioc_status != MPI2_IOCSTATUS_SUCCESS) {
+		printk(MPT2SAS_ERR_FMT "%s: iounit_pg3 failed with"\
+		    "ioc_status(0x%04x)\n", ioc->name, __func__, ioc_status);
+		goto out;
+	}
+
+	if (io_unit_pg3->GPIOCount < 25) {
+		printk(MPT2SAS_ERR_FMT "%s: iounit_pg3->GPIOCount less than"\
+		     "25 entries, detected (%d) entries\n", ioc->name, __func__,
+		    io_unit_pg3->GPIOCount);
+		goto out;
+	}
+
+	/* BRM status is in bit zero of GPIOVal[24] */
+	backup_rail_monitor_status = le16_to_cpu(io_unit_pg3->GPIOVal[24]);
+	rc = snprintf(buf, PAGE_SIZE, "%d\n", (backup_rail_monitor_status & 1));
+
+ out:
+	kfree(io_unit_pg3);
+	return rc;
+}
+static DEVICE_ATTR(BRM_status, S_IRUGO, _ctl_BRM_status_show, NULL);
+
 struct DIAG_BUFFER_START {
 	__le32 Size;
 	__le32 DiagVersion;
@@ -2901,6 +2970,7 @@ struct device_attribute *mpt2sas_host_attrs[] = {
 	&dev_attr_host_trace_buffer,
 	&dev_attr_host_trace_buffer_enable,
 	&dev_attr_reply_queue_count,
+	&dev_attr_BRM_status,
 	NULL,
 };