scsi: ufs: core: Add debugfs attributes for triggering the UFS EH

Make it easier to test the impact of the UFS error handler on software that
submits SCSI commands to the UFS driver.

Link: https://lore.kernel.org/r/20211020214024.2007615-8-bvanassche@acm.org
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs-debugfs.c

@@ -138,8 +138,73 @@ static void ufs_debugfs_restart_ee(struct work_struct *work)
 	ufs_debugfs_put_user_access(hba);
 }
 
+static int ufs_saved_err_show(struct seq_file *s, void *data)
+{
+	struct ufs_debugfs_attr *attr = s->private;
+	struct ufs_hba *hba = hba_from_file(s->file);
+	const int *p;
+
+	if (strcmp(attr->name, "saved_err") == 0) {
+		p = &hba->saved_err;
+	} else if (strcmp(attr->name, "saved_uic_err") == 0) {
+		p = &hba->saved_uic_err;
+	} else {
+		return -ENOENT;
+	}
+
+	seq_printf(s, "%d\n", *p);
+	return 0;
+}
+
+static ssize_t ufs_saved_err_write(struct file *file, const char __user *buf,
+				   size_t count, loff_t *ppos)
+{
+	struct ufs_debugfs_attr *attr = file->f_inode->i_private;
+	struct ufs_hba *hba = hba_from_file(file);
+	char val_str[16] = { };
+	int val, ret;
+
+	if (count > sizeof(val_str))
+		return -EINVAL;
+	if (copy_from_user(val_str, buf, count))
+		return -EFAULT;
+	ret = kstrtoint(val_str, 0, &val);
+	if (ret < 0)
+		return ret;
+
+	spin_lock_irq(hba->host->host_lock);
+	if (strcmp(attr->name, "saved_err") == 0) {
+		hba->saved_err = val;
+	} else if (strcmp(attr->name, "saved_uic_err") == 0) {
+		hba->saved_uic_err = val;
+	} else {
+		ret = -ENOENT;
+	}
+	if (ret == 0)
+		ufshcd_schedule_eh_work(hba);
+	spin_unlock_irq(hba->host->host_lock);
+
+	return ret < 0 ? ret : count;
+}
+
+static int ufs_saved_err_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, ufs_saved_err_show, inode->i_private);
+}
+
+static const struct file_operations ufs_saved_err_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ufs_saved_err_open,
+	.read		= seq_read,
+	.write		= ufs_saved_err_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 static const struct ufs_debugfs_attr ufs_attrs[] = {
 	{ "stats", 0400, &ufs_debugfs_stats_fops },
+	{ "saved_err", 0600, &ufs_saved_err_fops },
+	{ "saved_uic_err", 0600, &ufs_saved_err_fops },
 	{ }
 };