[PATCH 0/1] scsi: qla1280: Make 64-bit DMA addressing a Kconfig option

[Magnus Lindholm <linmag7@gmail.com>]

After spending quite some time trying to make the qla1280 driver work
with 64-bit DMA on alpha/tsunami systems with more than 2GB RAM, I
haven't given up on finding the root cause why this doesn't work but
I propose making 32/64 bit optional in the kernel config. Many thanks
to Martin, James, Maciej, Thomas and Christoph who has take the time
to provide feedback and testing during my attempts.

Some platforms like for example the SGI Octace2, require full 64-bit
addressing in order for the qla1280 driver to work. On other systems,
like the tsunami based Alpha systems, 32-bit PCI Qlogic SCSI controllers
(like the ISP1040 series) will not work properly on systems with more
than 2GB RAM installed. For some reason the combination of using PCI DAC
cycles and the enabling the DMA "monster window" on the tsunami based
alphas will result in file system corruption with the Qlogic ISP driver.
This is not the case on other alpha systems, such as rawhide based
systems, like the Alphaserver 4100, on this platform cards like
the qlogic 32-bit PCI (ISP1040B) works fine with PCI DAC cycles and
the "monster window" enabled. In order for the qla1280 driver to work
with ISP1040 chips on tsunami based alphas the driver must be compiled
with 32-bit DMA addressing. Most SRM firmware versions allow alphas to
boot from Qlogic ISP1040 SCSI controllers and hence having a simple way
to limit DMA addressing to 32-bits is relevant.

 drivers/scsi/Kconfig   | 17 +++++++++++++++++
 drivers/scsi/qla1280.c |  2 ++
 2 files changed, 19 insertions(+)

-- 
2.49.0