diff --git a/drivers/ata/pata_rb532_cf.c b/drivers/ata/pata_rb532_cf.c
index 8e3cdef..45f1e10 100644
--- a/drivers/ata/pata_rb532_cf.c
+++ b/drivers/ata/pata_rb532_cf.c
@@ -151,7 +151,7 @@
 	info->irq = irq;
 
 	info->iobase = devm_ioremap_nocache(&pdev->dev, res->start,
-				res->end - res->start + 1);
+				resource_size(res));
 	if (!info->iobase)
 		return -ENOMEM;