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: NRayagond Kokatanur <rayagond@vayavyalabs.com>
Signed-off-by: NGiuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/Kconfig

@@ -63,4 +63,22 @@ config STMMAC_RTC_TIMER
 
 endchoice
 
+choice
+	prompt "Select the DMA TX/RX descriptor operating modes"
+	depends on STMMAC_ETH
+	---help---
+	  This driver supports DMA descriptor to operate both in dual buffer
+	  (RING) and linked-list(CHAINED) mode. In RING mode each descriptor
+	  points to two data buffer pointers whereas in CHAINED mode they
+	  points to only one data buffer pointer.
+
+config STMMAC_RING
+	bool "Enable Descriptor Ring Mode"
+
+config STMMAC_CHAINED
+	bool "Enable Descriptor Chained Mode"
+
+endchoice
+
+
 endif

drivers/net/ethernet/stmicro/stmmac/Makefile

 obj-$(CONFIG_STMMAC_ETH) += stmmac.o
 stmmac-$(CONFIG_STMMAC_TIMER) += stmmac_timer.o
+stmmac-$(CONFIG_STMMAC_RING) += ring_mode.o
+stmmac-$(CONFIG_STMMAC_CHAINED) += chain_mode.o
 stmmac-objs:= stmmac_main.o stmmac_ethtool.o stmmac_mdio.o	\
 	      dwmac_lib.o dwmac1000_core.o  dwmac1000_dma.o	\
 	      dwmac100_core.o dwmac100_dma.o enh_desc.o  norm_desc.o \

drivers/net/ethernet/stmicro/stmmac/chain_mode.c

+/*******************************************************************************
+  Specialised functions for managing Chained 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"
+
+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;
+	unsigned int i = 1, len;
+
+	if (priv->plat->enh_desc)
+		bmax = BUF_SIZE_8KiB;
+	else
+		bmax = BUF_SIZE_2KiB;
+
+	len = nopaged_len - bmax;
+
+	desc->des2 = dma_map_single(priv->device, skb->data,
+				    bmax, DMA_TO_DEVICE);
+	priv->hw->desc->prepare_tx_desc(desc, 1, bmax, csum);
+
+	while (len != 0) {
+		entry = (++priv->cur_tx) % txsize;
+		desc = priv->dma_tx + entry;
+
+		if (len > bmax) {
+			desc->des2 = dma_map_single(priv->device,
+						    (skb->data + bmax * i),
+						    bmax, DMA_TO_DEVICE);
+			priv->hw->desc->prepare_tx_desc(desc, 0, bmax,
+							csum);
+			priv->hw->desc->set_tx_owner(desc);
+			priv->tx_skbuff[entry] = NULL;
+			len -= bmax;
+			i++;
+		} else {
+			desc->des2 = dma_map_single(priv->device,
+						    (skb->data + bmax * i), len,
+						    DMA_TO_DEVICE);
+			priv->hw->desc->prepare_tx_desc(desc, 0, len,
+							csum);
+			priv->hw->desc->set_tx_owner(desc);
+			priv->tx_skbuff[entry] = NULL;
+			len = 0;
+		}
+	}
+	return entry;
+}
+
+static unsigned int stmmac_is_jumbo_frm(int len, int enh_desc)
+{
+	unsigned int ret = 0;
+
+	if ((enh_desc && (len > BUF_SIZE_8KiB)) ||
+	    (!enh_desc && (len > BUF_SIZE_2KiB))) {
+		ret = 1;
+	}
+
+	return ret;
+}
+
+static void stmmac_refill_desc3(int bfsize, struct dma_desc *p)
+{
+}
+
+static void stmmac_init_desc3(int des3_as_data_buf, struct dma_desc *p)
+{
+}
+
+static void stmmac_clean_desc3(struct dma_desc *p)
+{
+}
+
+static void stmmac_init_dma_chain(struct dma_desc *des, dma_addr_t phy_addr,
+				  unsigned int size)
+{
+	/*
+	 * In chained mode the des3 points to the next element in the ring.
+	 * The latest element has to point to the head.
+	 */
+	int i;
+	struct dma_desc *p = des;
+	dma_addr_t dma_phy = phy_addr;
+
+	for (i = 0; i < (size - 1); i++) {
+		dma_phy += sizeof(struct dma_desc);
+		p->des3 = (unsigned int)dma_phy;
+		p++;
+	}
+	p->des3 = (unsigned int)phy_addr;
+}
+
+static int stmmac_set_16kib_bfsize(int mtu)
+{
+	/* Not supported */
+	return 0;
+}
+
+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,
+};

drivers/net/ethernet/stmicro/stmmac/common.h

@@ -287,10 +287,22 @@ struct mii_regs {
 	unsigned int data;	/* MII Data */
 };
 
+struct stmmac_ring_mode_ops {
+	unsigned int (*is_jumbo_frm) (int len, int ehn_desc);
+	unsigned int (*jumbo_frm) (void *priv, struct sk_buff *skb, int csum);
+	void (*refill_desc3) (int bfsize, struct dma_desc *p);
+	void (*init_desc3) (int des3_as_data_buf, struct dma_desc *p);
+	void (*init_dma_chain) (struct dma_desc *des, dma_addr_t phy_addr,
+				unsigned int size);
+	void (*clean_desc3) (struct dma_desc *p);
+	int (*set_16kib_bfsize) (int mtu);
+};
+
 struct mac_device_info {
 	const struct stmmac_ops		*mac;
 	const struct stmmac_desc_ops	*desc;
 	const struct stmmac_dma_ops	*dma;
+	const struct stmmac_ring_mode_ops	*ring;
 	struct mii_regs mii;	/* MII register Addresses */
 	struct mac_link link;
 	unsigned int synopsys_uid;
@@ -304,3 +316,4 @@ extern void stmmac_set_mac_addr(void __iomem *ioaddr, u8 addr[6],
 extern void stmmac_get_mac_addr(void __iomem *ioaddr, unsigned char *addr,
 				unsigned int high, unsigned int low);
 extern void dwmac_dma_flush_tx_fifo(void __iomem *ioaddr);
+extern const struct stmmac_ring_mode_ops ring_mode_ops;

drivers/net/ethernet/stmicro/stmmac/descs_com.h

+/*******************************************************************************
+  Header File to describe Normal/enhanced descriptor functions used for RING
+  and CHAINED modes.
+
+  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>
+*******************************************************************************/
+
+#if defined(CONFIG_STMMAC_RING)
+static inline void ehn_desc_rx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	p->des01.erx.buffer2_size = BUF_SIZE_8KiB - 1;
+	if (end)
+		p->des01.erx.end_ring = 1;
+}
+
+static inline void ehn_desc_tx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	if (end)
+		p->des01.etx.end_ring = 1;
+}
+
+static inline void enh_desc_end_tx_desc(struct dma_desc *p, int ter)
+{
+	p->des01.etx.end_ring = ter;
+}
+
+static inline void enh_set_tx_desc_len(struct dma_desc *p, int len)
+{
+	if (unlikely(len > BUF_SIZE_4KiB)) {
+		p->des01.etx.buffer1_size = BUF_SIZE_4KiB;
+		p->des01.etx.buffer2_size = len - BUF_SIZE_4KiB;
+	} else
+		p->des01.etx.buffer1_size = len;
+}
+
+static inline void ndesc_rx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	p->des01.rx.buffer2_size = BUF_SIZE_2KiB - 1;
+	if (end)
+		p->des01.rx.end_ring = 1;
+}
+
+static inline void ndesc_tx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	if (end)
+		p->des01.tx.end_ring = 1;
+}
+
+static inline void ndesc_end_tx_desc(struct dma_desc *p, int ter)
+{
+	p->des01.tx.end_ring = ter;
+}
+
+static inline void norm_set_tx_desc_len(struct dma_desc *p, int len)
+{
+	if (unlikely(len > BUF_SIZE_2KiB)) {
+		p->des01.etx.buffer1_size = BUF_SIZE_2KiB - 1;
+		p->des01.etx.buffer2_size = len - p->des01.etx.buffer1_size;
+	} else
+		p->des01.tx.buffer1_size = len;
+}
+
+#else
+
+static inline void ehn_desc_rx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	p->des01.erx.second_address_chained = 1;
+}
+
+static inline void ehn_desc_tx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	p->des01.etx.second_address_chained = 1;
+}
+
+static inline void enh_desc_end_tx_desc(struct dma_desc *p, int ter)
+{
+	p->des01.etx.second_address_chained = 1;
+}
+
+static inline void enh_set_tx_desc_len(struct dma_desc *p, int len)
+{
+	p->des01.etx.buffer1_size = len;
+}
+
+static inline void ndesc_rx_set_on_ring_chain(struct dma_desc *p, int end)
+{
+	p->des01.rx.second_address_chained = 1;
+}
+
+static inline void ndesc_tx_set_on_ring_chain(struct dma_desc *p, int ring_size)
+{
+	p->des01.tx.second_address_chained = 1;
+}
+
+static inline void ndesc_end_tx_desc(struct dma_desc *p, int ter)
+{
+	p->des01.tx.second_address_chained = 1;
+}
+
+static inline void norm_set_tx_desc_len(struct dma_desc *p, int len)
+{
+	p->des01.tx.buffer1_size = len;
+}
+#endif

drivers/net/ethernet/stmicro/stmmac/enh_desc.c

@@ -23,6 +23,7 @@
 *******************************************************************************/
 
 #include "common.h"
+#include "descs_com.h"
 
 static int enh_desc_get_tx_status(void *data, struct stmmac_extra_stats *x,
 				  struct dma_desc *p, void __iomem *ioaddr)
@@ -233,10 +234,9 @@ static void enh_desc_init_rx_desc(struct dma_desc *p, unsigned int ring_size,
 	for (i = 0; i < ring_size; i++) {
 		p->des01.erx.own = 1;
 		p->des01.erx.buffer1_size = BUF_SIZE_8KiB - 1;
-		/* To support jumbo frames */
-		p->des01.erx.buffer2_size = BUF_SIZE_8KiB - 1;
-		if (i == ring_size - 1)
-			p->des01.erx.end_ring = 1;
+
+		ehn_desc_rx_set_on_ring_chain(p, (i == ring_size - 1));
+
 		if (disable_rx_ic)
 			p->des01.erx.disable_ic = 1;
 		p++;
@@ -249,8 +249,7 @@ static void enh_desc_init_tx_desc(struct dma_desc *p, unsigned int ring_size)
 
 	for (i = 0; i < ring_size; i++) {
 		p->des01.etx.own = 0;
-		if (i == ring_size - 1)
-			p->des01.etx.end_ring = 1;
+		ehn_desc_tx_set_on_ring_chain(p, (i == ring_size - 1));
 		p++;
 	}
 }
@@ -285,19 +284,16 @@ static void enh_desc_release_tx_desc(struct dma_desc *p)
 	int ter = p->des01.etx.end_ring;
 
 	memset(p, 0, offsetof(struct dma_desc, des2));
-	p->des01.etx.end_ring = ter;
+	enh_desc_end_tx_desc(p, ter);
 }
 
 static void enh_desc_prepare_tx_desc(struct dma_desc *p, int is_fs, int len,
 				     int csum_flag)
 {
 	p->des01.etx.first_segment = is_fs;
-	if (unlikely(len > BUF_SIZE_4KiB)) {
-		p->des01.etx.buffer1_size = BUF_SIZE_4KiB;
-		p->des01.etx.buffer2_size = len - BUF_SIZE_4KiB;
-	} else {
-		p->des01.etx.buffer1_size = len;
-	}
+
+	enh_set_tx_desc_len(p, len);
+
 	if (likely(csum_flag))
 		p->des01.etx.checksum_insertion = cic_full;
 }

drivers/net/ethernet/stmicro/stmmac/norm_desc.c

@@ -23,6 +23,7 @@
 *******************************************************************************/
 
 #include "common.h"
+#include "descs_com.h"
 
 static int ndesc_get_tx_status(void *data, struct stmmac_extra_stats *x,
 			       struct dma_desc *p, void __iomem *ioaddr)
@@ -126,9 +127,9 @@ static void ndesc_init_rx_desc(struct dma_desc *p, unsigned int ring_size,
 	for (i = 0; i < ring_size; i++) {
 		p->des01.rx.own = 1;
 		p->des01.rx.buffer1_size = BUF_SIZE_2KiB - 1;
-		p->des01.rx.buffer2_size = BUF_SIZE_2KiB - 1;
-		if (i == ring_size - 1)
-			p->des01.rx.end_ring = 1;
+
+		ndesc_rx_set_on_ring_chain(p, (i == ring_size - 1));
+
 		if (disable_rx_ic)
 			p->des01.rx.disable_ic = 1;
 		p++;
@@ -140,8 +141,7 @@ static void ndesc_init_tx_desc(struct dma_desc *p, unsigned int ring_size)
 	int i;
 	for (i = 0; i < ring_size; i++) {
 		p->des01.tx.own = 0;
-		if (i == ring_size - 1)
-			p->des01.tx.end_ring = 1;
+		ndesc_tx_set_on_ring_chain(p, (i == (ring_size - 1)));
 		p++;
 	}
 }
@@ -176,20 +176,14 @@ static void ndesc_release_tx_desc(struct dma_desc *p)
 	int ter = p->des01.tx.end_ring;
 
 	memset(p, 0, offsetof(struct dma_desc, des2));
-	/* set termination field */
-	p->des01.tx.end_ring = ter;
+	ndesc_end_tx_desc(p, ter);
 }
 
 static void ndesc_prepare_tx_desc(struct dma_desc *p, int is_fs, int len,
 				  int csum_flag)
 {
 	p->des01.tx.first_segment = is_fs;
-
-	if (unlikely(len > BUF_SIZE_2KiB)) {
-		p->des01.etx.buffer1_size = BUF_SIZE_2KiB - 1;
-		p->des01.etx.buffer2_size = len - p->des01.etx.buffer1_size;
-	} else
-		p->des01.tx.buffer1_size = len;
+	norm_set_tx_desc_len(p, len);
 }
 
 static void ndesc_clear_tx_ic(struct dma_desc *p)

drivers/net/ethernet/stmicro/stmmac/ring_mode.c

+/*******************************************************************************
+  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,
+};

drivers/net/ethernet/stmicro/stmmac/stmmac.h

@@ -22,7 +22,7 @@
 
 #define DRV_MODULE_VERSION	"Oct_2011"
 #include <linux/stmmac.h>
-
+#include <linux/phy.h>
 #include "common.h"
 #ifdef CONFIG_STMMAC_TIMER
 #include "stmmac_timer.h"

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -2,7 +2,7 @@
   This is the driver for the ST MAC 10/100/1000 on-chip Ethernet controllers.
   ST Ethernet IPs are built around a Synopsys IP Core.
 
-  Copyright (C) 2007-2009  STMicroelectronics Ltd
+	Copyright(C) 2007-2011 STMicroelectronics Ltd
 
   This program is free software; you can redistribute it and/or modify it
   under the terms and conditions of the GNU General Public License,
@@ -41,17 +41,16 @@
 #include <linux/if_ether.h>
 #include <linux/crc32.h>
 #include <linux/mii.h>
-#include <linux/phy.h>
 #include <linux/if.h>
 #include <linux/if_vlan.h>
 #include <linux/dma-mapping.h>
 #include <linux/slab.h>
 #include <linux/prefetch.h>
-#include "stmmac.h"
 #ifdef CONFIG_STMMAC_DEBUG_FS
 #include <linux/debugfs.h>
 #include <linux/seq_file.h>
 #endif
+#include "stmmac.h"
 
 #define STMMAC_RESOURCE_NAME	"stmmaceth"
 
@@ -388,11 +387,28 @@ static void display_ring(struct dma_desc *p, int size)
 	}
 }
 
+static int stmmac_set_bfsize(int mtu, int bufsize)
+{
+	int ret = bufsize;
+
+	if (mtu >= BUF_SIZE_4KiB)
+		ret = BUF_SIZE_8KiB;
+	else if (mtu >= BUF_SIZE_2KiB)
+		ret = BUF_SIZE_4KiB;
+	else if (mtu >= DMA_BUFFER_SIZE)
+		ret = BUF_SIZE_2KiB;
+	else
+		ret = DMA_BUFFER_SIZE;
+
+	return ret;
+}
+
 /**
  * init_dma_desc_rings - init the RX/TX descriptor rings
  * @dev: net device structure
  * Description:  this function initializes the DMA RX/TX descriptors
- * and allocates the socket buffers.
+ * and allocates the socket buffers. It suppors the chained and ring
+ * modes.
  */
 static void init_dma_desc_rings(struct net_device *dev)
 {
@@ -401,31 +417,24 @@ static void init_dma_desc_rings(struct net_device *dev)
 	struct sk_buff *skb;
 	unsigned int txsize = priv->dma_tx_size;
 	unsigned int rxsize = priv->dma_rx_size;
-	unsigned int bfsize = priv->dma_buf_sz;
-	int buff2_needed = 0, dis_ic = 0;
+	unsigned int bfsize;
+	int dis_ic = 0;
+	int des3_as_data_buf = 0;
 
-	/* Set the Buffer size according to the MTU;
-	 * indeed, in case of jumbo we need to bump-up the buffer sizes.
-	 */
-	if (unlikely(dev->mtu >= BUF_SIZE_8KiB))
-		bfsize = BUF_SIZE_16KiB;
-	else if (unlikely(dev->mtu >= BUF_SIZE_4KiB))
-		bfsize = BUF_SIZE_8KiB;
-	else if (unlikely(dev->mtu >= BUF_SIZE_2KiB))
-		bfsize = BUF_SIZE_4KiB;
-	else if (unlikely(dev->mtu >= DMA_BUFFER_SIZE))
-		bfsize = BUF_SIZE_2KiB;
+	/* Set the max buffer size according to the DESC mode
+	 * and the MTU. Note that RING mode allows 16KiB bsize. */
+	bfsize = priv->hw->ring->set_16kib_bfsize(dev->mtu);
+
+	if (bfsize == BUF_SIZE_16KiB)
+		des3_as_data_buf = 1;
 	else
-		bfsize = DMA_BUFFER_SIZE;
+		bfsize = stmmac_set_bfsize(dev->mtu, priv->dma_buf_sz);
 
 #ifdef CONFIG_STMMAC_TIMER
 	/* Disable interrupts on completion for the reception if timer is on */
 	if (likely(priv->tm->enable))
 		dis_ic = 1;
 #endif
-	/* If the MTU exceeds 8k so use the second buffer in the chain */
-	if (bfsize >= BUF_SIZE_8KiB)
-		buff2_needed = 1;
 
 	DBG(probe, INFO, "stmmac: txsize %d, rxsize %d, bfsize %d\n",
 	    txsize, rxsize, bfsize);
@@ -453,7 +462,7 @@ static void init_dma_desc_rings(struct net_device *dev)
 		return;
 	}
 
-	DBG(probe, INFO, "stmmac (%s) DMA desc rings: virt addr (Rx %p, "
+	DBG(probe, INFO, "stmmac (%s) DMA desc: virt addr (Rx %p, "
 	    "Tx %p)\n\tDMA phy addr (Rx 0x%08x, Tx 0x%08x)\n",
 	    dev->name, priv->dma_rx, priv->dma_tx,
 	    (unsigned int)priv->dma_rx_phy, (unsigned int)priv->dma_tx_phy);
@@ -475,8 +484,9 @@ static void init_dma_desc_rings(struct net_device *dev)
 						bfsize, DMA_FROM_DEVICE);
 
 		p->des2 = priv->rx_skbuff_dma[i];
-		if (unlikely(buff2_needed))
-			p->des3 = p->des2 + BUF_SIZE_8KiB;
+
+		priv->hw->ring->init_desc3(des3_as_data_buf, p);
+
 		DBG(probe, INFO, "[%p]\t[%p]\t[%x]\n", priv->rx_skbuff[i],
 			priv->rx_skbuff[i]->data, priv->rx_skbuff_dma[i]);
 	}
@@ -490,6 +500,12 @@ static void init_dma_desc_rings(struct net_device *dev)
 		priv->tx_skbuff[i] = NULL;
 		priv->dma_tx[i].des2 = 0;
 	}
+
+	/* In case of Chained mode this sets the des3 to the next
+	 * element in the chain */
+	priv->hw->ring->init_dma_chain(priv->dma_rx, priv->dma_rx_phy, rxsize);
+	priv->hw->ring->init_dma_chain(priv->dma_tx, priv->dma_tx_phy, txsize);
+
 	priv->dirty_tx = 0;
 	priv->cur_tx = 0;
 
@@ -620,8 +636,7 @@ static void stmmac_tx(struct stmmac_priv *priv)
 			dma_unmap_single(priv->device, p->des2,
 					 priv->hw->desc->get_tx_len(p),
 					 DMA_TO_DEVICE);
-		if (unlikely(p->des3))
-			p->des3 = 0;
+		priv->hw->ring->clean_desc3(p);
 
 		if (likely(skb != NULL)) {
 			/*
@@ -728,7 +743,6 @@ static void stmmac_no_timer_stopped(void)
  */
 static void stmmac_tx_err(struct stmmac_priv *priv)
 {
-
 	netif_stop_queue(priv->dev);
 
 	priv->hw->dma->stop_tx(priv->ioaddr);
@@ -1028,47 +1042,6 @@ static int stmmac_release(struct net_device *dev)
 	return 0;
 }
 
-static unsigned int stmmac_handle_jumbo_frames(struct sk_buff *skb,
-					       struct net_device *dev,
-					       int csum_insertion)
-{
-	struct stmmac_priv *priv = netdev_priv(dev);
-	unsigned int nopaged_len = skb_headlen(skb);
-	unsigned int txsize = priv->dma_tx_size;
-	unsigned int entry = priv->cur_tx % txsize;
-	struct dma_desc *desc = priv->dma_tx + entry;
-
-	if (nopaged_len > BUF_SIZE_8KiB) {
-
-		int buf2_size = nopaged_len - BUF_SIZE_8KiB;
-
-		desc->des2 = dma_map_single(priv->device, skb->data,
-					    BUF_SIZE_8KiB, DMA_TO_DEVICE);
-		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
-		priv->hw->desc->prepare_tx_desc(desc, 1, BUF_SIZE_8KiB,
-						csum_insertion);
-
-		entry = (++priv->cur_tx) % txsize;
-		desc = priv->dma_tx + entry;
-
-		desc->des2 = dma_map_single(priv->device,
-					skb->data + BUF_SIZE_8KiB,
-					buf2_size, DMA_TO_DEVICE);
-		desc->des3 = desc->des2 + BUF_SIZE_4KiB;
-		priv->hw->desc->prepare_tx_desc(desc, 0, buf2_size,
-						csum_insertion);
-		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_insertion);
-	}
-	return entry;
-}
-
 /**
  *  stmmac_xmit:
  *  @skb : the socket buffer
@@ -1083,6 +1056,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	int i, csum_insertion = 0;
 	int nfrags = skb_shinfo(skb)->nr_frags;
 	struct dma_desc *desc, *first;
+	unsigned int nopaged_len = skb_headlen(skb);
 
 	if (unlikely(stmmac_tx_avail(priv) < nfrags + 1)) {
 		if (!netif_queue_stopped(dev)) {
@@ -1103,7 +1077,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 		pr_info("stmmac xmit:\n"
 		       "\tskb addr %p - len: %d - nopaged_len: %d\n"
 		       "\tn_frags: %d - ip_summed: %d - %s gso\n",
-		       skb, skb->len, skb_headlen(skb), nfrags, skb->ip_summed,
+		       skb, skb->len, nopaged_len, nfrags, skb->ip_summed,
 		       !skb_is_gso(skb) ? "isn't" : "is");
 #endif
 
@@ -1116,14 +1090,14 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	if ((nfrags > 0) || (skb->len > ETH_FRAME_LEN))
 		pr_debug("stmmac xmit: skb len: %d, nopaged_len: %d,\n"
 		       "\t\tn_frags: %d, ip_summed: %d\n",
-		       skb->len, skb_headlen(skb), nfrags, skb->ip_summed);
+		       skb->len, nopaged_len, nfrags, skb->ip_summed);
 #endif
 	priv->tx_skbuff[entry] = skb;
-	if (unlikely(skb->len >= BUF_SIZE_4KiB)) {
-		entry = stmmac_handle_jumbo_frames(skb, dev, csum_insertion);
+
+	if (priv->hw->ring->is_jumbo_frm(skb->len, priv->plat->enh_desc)) {
+		entry = priv->hw->ring->jumbo_frm(priv, skb, csum_insertion);
 		desc = priv->dma_tx + entry;
 	} else {
-		unsigned int nopaged_len = skb_headlen(skb);
 		desc->des2 = dma_map_single(priv->device, skb->data,
 					nopaged_len, DMA_TO_DEVICE);
 		priv->hw->desc->prepare_tx_desc(desc, 1, nopaged_len,
@@ -1214,11 +1188,10 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
 					   DMA_FROM_DEVICE);
 
 			(p + entry)->des2 = priv->rx_skbuff_dma[entry];
-			if (unlikely(priv->plat->has_gmac)) {
-				if (bfsize >= BUF_SIZE_8KiB)
-					(p + entry)->des3 =
-					    (p + entry)->des2 + BUF_SIZE_8KiB;
-			}
+
+			if (unlikely(priv->plat->has_gmac))
+				priv->hw->ring->refill_desc3(bfsize, p + entry);
+
 			RX_DBG(KERN_INFO "\trefill entry #%d\n", entry);
 		}
 		wmb();
@@ -1795,6 +1768,7 @@ static int stmmac_mac_device_setup(struct net_device *dev)
 		device->desc = &ndesc_ops;
 
 	priv->hw = device;
+	priv->hw->ring = &ring_mode_ops;
 
 	if (device_can_wakeup(priv->device)) {
 		priv->wolopts = WAKE_MAGIC; /* Magic Frame as default */