[PATCH 1/1] scsi: qla1280: Make 64-bit DMA addressing a Kconfig option

[Magnus Lindholm <linmag7@gmail.com>]

Make 64-bit DMA addressing a Kconfig option.

While defaulting to 64-bit addressing, this gives the user the option
to revert to 32-bits when necessary without messing with the kernel
source. The Kconfig help text also points out the issues with tsunami
based alphas with more than 2GB RAM and 32-bit PCI Qlogic SCSI
controllers.

Signed-off-by: Magnus Lindholm <linmag7@gmail.com>
---
 drivers/scsi/Kconfig   | 17 +++++++++++++++++
 drivers/scsi/qla1280.c |  2 ++
 2 files changed, 19 insertions(+)

diff --git a/drivers/scsi/Kconfig b/drivers/scsi/Kconfig
index 5522310bab8d..27cf94f374f4 100644
--- a/drivers/scsi/Kconfig
+++ b/drivers/scsi/Kconfig
@@ -1126,6 +1126,23 @@ config SCSI_QLOGIC_1280
 	  To compile this driver as a module, choose M here: the
 	  module will be called qla1280.
 
+config SCSI_QLOGIC_1280_DMA_64BIT_ADDRESSING
+        bool "Enable 64-bit DMA addressing mode"
+        depends on SCSI_QLOGIC_1280
+        default y
+        help
+	  This options enables full 64-bit addressing for Qlogic ISP
+	  chips. 64-bit addressing works on most platforms and is hence
+	  the default. Some platforms like for example the SGI Octace2,
+	  require full 64-bit addressing in order to work and must have
+	  this option enabled.
+
+	  On some systems, like tsunami based Alpha systems, 32-bit
+	  PCI Qlogic SCSI controllers will not work propberly on systems
+	  with more than 2GB RAM installed. If you are on a tsunami
+	  based alpha (like the ES40, DS20) and want to use cards with
+	  the ISP1040/1020 chip, you should say no here.
+
 config SCSI_QLOGICPTI
 	tristate "PTI Qlogic, ISP Driver"
 	depends on SBUS && SCSI
diff --git a/drivers/scsi/qla1280.c b/drivers/scsi/qla1280.c
index 6af018f1ca22..d02141157abe 100644
--- a/drivers/scsi/qla1280.c
+++ b/drivers/scsi/qla1280.c
@@ -371,8 +371,10 @@
 #include "qla1280.h"
 
 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
+#ifdef CONFIG_SCSI_QLOGIC_1280_DMA_64BIT_ADDRESSING
 #define QLA_64BIT_PTR	1
 #endif
+#endif
 
 #define NVRAM_DELAY()			udelay(500)	/* 2 microseconds */
 
-- 
2.49.0