netdev - [patch 1/4] de2104x: support for systems lacking cache coherence

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Message-Id: <200906101955.n5AJt0Zr008180@imap1.linux-foundation.org>
Date:	Wed, 10 Jun 2009 12:55:00 -0700
From:	akpm@...ux-foundation.org
To:	davem@...emloft.net
Cc:	netdev@...r.kernel.org, akpm@...ux-foundation.org,
	risto.suominen@...il.com, Risto.Suominen@...il.com,
	grundler@...isc-linux.org
Subject: [patch 1/4] de2104x: support for systems lacking cache coherence

From: Risto Suominen <risto.suominen@...il.com>

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@...il.com>
Cc: Grant Grundler <grundler@...isc-linux.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 drivers/net/tulip/Kconfig   |   12 ++++++++++++
 drivers/net/tulip/de2104x.c |   13 ++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff -puN drivers/net/tulip/Kconfig~de2104x-support-for-systems-lacking-cache-coherence drivers/net/tulip/Kconfig
--- a/drivers/net/tulip/Kconfig~de2104x-support-for-systems-lacking-cache-coherence
+++ a/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
diff -puN drivers/net/tulip/de2104x.c~de2104x-support-for-systems-lacking-cache-coherence drivers/net/tulip/de2104x.c
--- a/drivers/net/tulip/de2104x.c~de2104x-support-for-systems-lacking-cache-coherence
+++ a/drivers/net/tulip/de2104x.c
@@ -82,6 +82,13 @@ MODULE_PARM_DESC (rx_copybreak, "de2104x
 				 NETIF_MSG_RX_ERR	| \
 				 NETIF_MSG_TX_ERR)
 
+/* Descriptor skip length in 32 bit longwords. */
+#ifndef CONFIG_DE2104X_DSL
+#define DSL			0
+#else
+#define DSL			CONFIG_DE2104X_DSL
+#endif
+
 #define DE_RX_RING_SIZE		64
 #define DE_TX_RING_SIZE		64
 #define DE_RING_BYTES		\
@@ -153,6 +160,7 @@ enum {
 	CmdReset		= (1 << 0),
 	CacheAlign16		= 0x00008000,
 	BurstLen4		= 0x00000400,
+	DescSkipLen		= (DSL << 2),
 
 	/* Rx/TxPoll bits */
 	NormalTxPoll		= (1 << 0),
@@ -246,7 +254,7 @@ static const u32 de_intr_mask =
  * Set the programmable burst length to 4 longwords for all:
  * DMA errors result without these values. Cache align 16 long.
  */
-static const u32 de_bus_mode = CacheAlign16 | BurstLen4;
+static const u32 de_bus_mode = CacheAlign16 | BurstLen4 | DescSkipLen;
 
 struct de_srom_media_block {
 	u8			opts;
@@ -266,6 +274,9 @@ struct de_desc {
 	__le32			opts2;
 	__le32			addr1;
 	__le32			addr2;
+#if DSL
+	__le32			skip[DSL];
+#endif
 };
 
 struct media_info {
_
--
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