On Friday 06 April 2012, Chris Metcalf wrote:

This change adds support for the tilegx network driver based on the
GXIO IORPC support in the tilegx software stack, using the on-chip
mPIPE packet processing engine.

Signed-off-by: Chris Metcalf <redacted>
---
 drivers/net/ethernet/tile/Kconfig  |    1 +
 drivers/net/ethernet/tile/Makefile |    4 +-
 drivers/net/ethernet/tile/tilegx.c | 2045 ++++++++++++++++++++++++++++++++++++
 3 files changed, 2048 insertions(+), 2 deletions(-)
 create mode 100644 drivers/net/ethernet/tile/tilegx.c

I think the directory name should be the company, not the architecture here, so make
it drivers/net/ethernet/tilera/tilegx.c instead.

+
+MODULE_AUTHOR("Tilera");
+MODULE_LICENSE("GPL");
+

MODULE_AUTHOR is normally a real person with an email address.

+/* Statistics counters for a specific cpu and device. */
+struct tile_net_stats_t {
+	u32 rx_packets;
+	u32 rx_bytes;
+	u32 tx_packets;
+	u32 tx_bytes;
+};

I think you need to drop the _t postfix here, which presumably comes
from converting it from a typedef.

+
+/* The actual devices. */
+static struct net_device *tile_net_devs[TILE_NET_DEVS];
+
+/* The device for a given channel.  HACK: We use "32", not
+ * TILE_NET_CHANNELS, because it is fairly subtle that the 5 bit
+ * "idesc.channel" field never exceeds TILE_NET_CHANNELS.
+ */
+static struct net_device *tile_net_devs_for_channel[32];

When you need to keep a list or array of device structures in a driver, you're
usually doing something very wrong. The convention is to just pass the pointer
around to where you need it.

+
+/* Convert a "buffer ptr" into a "buffer cpa". */
+static inline void *buf_to_cpa(void *buf)
+{
+	return (void *)__pa(buf);
+}
+
+
+/* Convert a "buffer cpa" into a "buffer ptr". */
+static inline void *cpa_to_buf(void *cpa)
+{
+	return (void *)__va(cpa);
+}

This is almost certainly wrong: The type returned by __pa is a phys_addr_t,
which cannot be dereferenced like a pointer. On normal drivers, you would
use dma_map_single()/dma_unmap_single() to get a token that can get
passed into a dma engine. From what I can tell, this device is directly mapped,
while your PCI uses an IOMMU, so that would require two different
implementations of dma mapping operations.

+/* Allocate and push a buffer. */
+static bool tile_net_provide_buffer(bool small)
+{
+	int stack = small ? small_buffer_stack : large_buffer_stack;
+
+	/* Buffers must be aligned. */
+	const unsigned long align = 128;
+
+	/* Note that "dev_alloc_skb()" adds NET_SKB_PAD more bytes,
+	 * and also "reserves" that many bytes.
+	 */
+	int len = sizeof(struct sk_buff **) + align + (small ? 128 : 1664);
+
+	/* Allocate (or fail). */
+	struct sk_buff *skb = dev_alloc_skb(len);
+	if (skb == NULL)
+		return false;
+
+	/* Make room for a back-pointer to 'skb'. */
+	skb_reserve(skb, sizeof(struct sk_buff **));
+
+	/* Make sure we are aligned. */
+	skb_reserve(skb, -(long)skb->data & (align - 1));
+
+	/* Save a back-pointer to 'skb'. */
+	*(struct sk_buff **)(skb->data - sizeof(struct sk_buff **)) = skb;

This looks very wrong: why would you put the pointer to the skb into the
skb itself?

+	/* Make sure "skb" and the back-pointer have been flushed. */
+	__insn_mf();

Try to use archicture independent names for flush operations like this
to make it more readable. I assume this should be smp_wmb()?

+
+		/* Compute the "ip checksum". */
+		jsum = isum_hack + htons(s_len - eh_len) + htons(id);
+		jsum = __insn_v2sadu(jsum, 0);
+		jsum = __insn_v2sadu(jsum, 0);
+		jsum = (0xFFFF ^ jsum);
+		jh->check = jsum;
+
+		/* Update the tcp "seq". */
+		uh->seq = htonl(seq);
+
+		/* Update some flags. */
+		if (!final)
+			uh->fin = uh->psh = 0;
+
+		/* Compute the tcp pseudo-header checksum. */
+		usum = tsum_hack + htons(s_len);
+		usum = __insn_v2sadu(usum, 0);
+		usum = __insn_v2sadu(usum, 0);
+		uh->check = usum;

Why to you open-code the ip checksum functions here? Normally the stack takes
care of this by calling the functions you already provide in
arch/tile/lib/checksum.c

	Arnd