stmmac: add CHAINED descriptor mode support (V4)

This patch enhances the STMMAC driver to support CHAINED mode of
descriptor.

STMMAC supports DMA descriptor to operate both in dual buffer(RING)
and linked-list(CHAINED) mode. In RING mode (default) each descriptor
points to two data buffer pointers whereas in CHAINED mode they point
to only one data buffer pointer.

In CHAINED mode each descriptor will have pointer to next descriptor in
the list, hence creating the explicit chaining in the descriptor itself,
whereas such explicit chaining is not possible in RING mode.

First version of this work has been done by Rayagond.
Then the patch has been reworked avoiding ifdef inside the C code.
A new header file has been added to define all the functions needed for
managing enhanced and normal descriptors.
In fact, these have to be specialized according to the ring/chain usage.
Two new C files have been also added to implement the helper routines
needed to manage: jumbo frames, chain and ring setup (i.e. desc3).

Signed-off-by: Rayagond Kokatanur <rayagond@vayavyalabs.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 126 insertions, 0 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/ring_mode.c b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
new file mode 100644
index 000000000000..fb8377da1687
--- /dev/null
+++ b/drivers/net/ethernet/stmicro/stmmac/ring_mode.c
@@ -0,0 +1,126 @@
+/*******************************************************************************
+  Specialised functions for managing Ring mode
+
+  Copyright(C) 2011  STMicroelectronics Ltd
+
+  It defines all the functions used to handle the normal/enhanced
+  descriptors in case of the DMA is configured to work in chained or
+  in ring mode.
+
+  This program is free software; you can redistribute it and/or modify it
+  under the terms and conditions of the GNU General Public License,
+  version 2, as published by the Free Software Foundation.
+
+  This program is distributed in the hope it will be useful, but WITHOUT
+  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+  more details.
+
+  You should have received a copy of the GNU General Public License along with
+  this program; if not, write to the Free Software Foundation, Inc.,
+  51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
+
+  The full GNU General Public License is included in this distribution in
+  the file called "COPYING".
+
+  Author: Giuseppe Cavallaro <peppe.cavallaro@st.com>
+*******************************************************************************/
+
+#include "stmmac.h"
+
+static unsigned int stmmac_jumbo_frm(void *p, struct sk_buff *skb, int csum)
+{
+	struct stmmac_priv *priv = (struct stmmac_priv *) p;
+	unsigned int txsize = priv->dma_tx_size;
+	unsigned int entry = priv->cur_tx % txsize;
+	struct dma_desc *desc = priv->dma_tx + entry;
+	unsigned int nopaged_len = skb_headlen(skb);
+	unsigned int bmax, len;
+
+	if (priv->plat->enh_desc)
+		bmax = BUF_SIZE_8KiB;
+	else
+		bmax = BUF_SIZE_2KiB;
+
+	len = nopaged_len - bmax;
+
+	if (nopaged_len > BUF_SIZE_8KiB) {
+
+		desc->des2 = dma_map_single(priv->device, skb->data,
+					    bmax, DMA_TO_DEVICE);
+		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
+		priv->hw->desc->prepare_tx_desc(desc, 1, bmax,
+						csum);
+
+		entry = (++priv->cur_tx) % txsize;
+		desc = priv->dma_tx + entry;
+
+		desc->des2 = dma_map_single(priv->device, skb->data + bmax,
+					    len, DMA_TO_DEVICE);
+		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
+		priv->hw->desc->prepare_tx_desc(desc, 0, len, csum);
+		priv->hw->desc->set_tx_owner(desc);
+		priv->tx_skbuff[entry] = NULL;
+	} else {
+		desc->des2 = dma_map_single(priv->device, skb->data,
+					    nopaged_len, DMA_TO_DEVICE);
+		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
+		priv->hw->desc->prepare_tx_desc(desc, 1, nopaged_len, csum);
+	}
+
+	return entry;
+}
+
+static unsigned int stmmac_is_jumbo_frm(int len, int enh_desc)
+{
+	unsigned int ret = 0;
+
+	if (len >= BUF_SIZE_4KiB)
+		ret = 1;
+
+	return ret;
+}
+
+static void stmmac_refill_desc3(int bfsize, struct dma_desc *p)
+{
+	/* Fill DES3 in case of RING mode */
+	if (bfsize >= BUF_SIZE_8KiB)
+		p->des3 = p->des2 + BUF_SIZE_8KiB;
+}
+
+/* In ring mode we need to fill the desc3 because it is used
+ * as buffer */
+static void stmmac_init_desc3(int des3_as_data_buf, struct dma_desc *p)
+{
+	if (unlikely(des3_as_data_buf))
+		p->des3 = p->des2 + BUF_SIZE_8KiB;
+}
+
+static void stmmac_init_dma_chain(struct dma_desc *des, dma_addr_t phy_addr,
+				  unsigned int size)
+{
+}
+
+static void stmmac_clean_desc3(struct dma_desc *p)
+{
+	if (unlikely(p->des3))
+		p->des3 = 0;
+}
+
+static int stmmac_set_16kib_bfsize(int mtu)
+{
+	int ret = 0;
+	if (unlikely(mtu >= BUF_SIZE_8KiB))
+		ret = BUF_SIZE_16KiB;
+	return ret;
+}
+
+const struct stmmac_ring_mode_ops ring_mode_ops = {
+	.is_jumbo_frm = stmmac_is_jumbo_frm,
+	.jumbo_frm = stmmac_jumbo_frm,
+	.refill_desc3 = stmmac_refill_desc3,
+	.init_desc3 = stmmac_init_desc3,
+	.init_dma_chain = stmmac_init_dma_chain,
+	.clean_desc3 = stmmac_clean_desc3,
+	.set_16kib_bfsize = stmmac_set_16kib_bfsize,
+};