de2104x: support for systems lacking cache coherence

Add a configurable Descriptor Skip Length for systems that lack cache
coherence.

(akpm: I think this should be done as a module parameter, not a
compile-tinme option)

Signed-off-by: Risto Suominen <Risto.Suominen@gmail.com>
Cc: Grant Grundler <grundler@parisc-linux.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/net/tulip/Kconfig b/drivers/net/tulip/Kconfig
index d913405bc393..1cc8cf4425d1 100644
--- a/drivers/net/tulip/Kconfig
+++ b/drivers/net/tulip/Kconfig
@@ -27,6 +27,18 @@ config DE2104X
           To compile this driver as a module, choose M here. The module will
           be called de2104x.
 
+config DE2104X_DSL
+        int "Descriptor Skip Length in 32 bit longwords"
+        depends on DE2104X
+        range 0 31
+        default 0
+        help
+          Setting this value allows to align ring buffer descriptors into their
+          own cache lines. Value of 4 corresponds to the typical 32 byte line
+          (the descriptor is 16 bytes). This is necessary on systems that lack
+          cache coherence, an example is PowerMac 5500. Otherwise 0 is safe.
+          Default is 0, and range is 0 to 31.
+
 config TULIP
         tristate "DECchip Tulip (dc2114x) PCI support"
         depends on PCI