Port FEATURE_CONF_DESC_LENGTH from the grx500 variant of the driver.
This also reduces the default length of some descriptors, resulting in
significantly lower latencies when the line is saturated.

--- a/dcdp/inc/tc_common.h
+++ b/dcdp/inc/tc_common.h
@@ -27,7 +27,11 @@
 #define UMT_DEF_PERIOD		400	/* microseconds */
 
 #define MAX_MTU			(DMA_PACKET_SZ - ETH_HLEN - HD_RSRV_SZ)
+#ifdef FEATURE_CONF_DESC_LENGTH
+#define QOSQ_NUM		8
+#else
 #define QOSQ_NUM		2
+#endif
 #define FW_STOP_TIMEOUT		20	/* millisecond */
 #define QOS_DISPATCH_OWN	0
 #define ACA_TXIN_POLL_INTVAL	10	/* millisecond */
--- a/dcdp/inc/tc_main.h
+++ b/dcdp/inc/tc_main.h
@@ -30,6 +30,7 @@
 #define TCPRIV_ALIGN	32
 #define DMA_PACKET_SZ	2048
 
+#define FEATURE_CONF_DESC_LENGTH 1
 #define FEATURE_POWER_DOWN 1
 
 enum {
@@ -157,6 +158,25 @@ struct tc_param {
 	unsigned int txout_dnum;
 	unsigned int rxin_dnum;
 	unsigned int rxout_dnum;
+
+#ifdef FEATURE_CONF_DESC_LENGTH
+	/* __US_FAST_PATH_DES_LIST_NUM:64
+	 * __ACA_TX_IN_PD_LIST_NUM
+	 * __ACA_TX_OUT_PD_LIST_NUM
+	 * */
+	u32 conf_us_fp_desq_len;
+	/*
+	 * Number of queue per QoS queue: QOS_DES_NUM / QOSQ_NUM
+	 * */
+	u32 conf_us_qos_queue_len;
+	/* __US_OUTQ0_DES_LIST_NUM: 32
+	 * __US_OUTQ1_DES_LIST_NUM: 32
+	 * OUTQ_DESC_PER_Q
+	 * */
+	u32 conf_us_outq_len;
+	/**/
+	u32 conf_us_local_q0_desq_len;
+#endif
 };
 
 struct cdma {
--- a/dcdp/ptm_tc.c
+++ b/dcdp/ptm_tc.c
@@ -75,7 +75,11 @@ static const u32 tx_kvec[] = {
 	0x30B1B233, 0xB43536B7, 0xB8393ABB, 0x3CBDBE3F,
 	0xC04142C3, 0x44C5C647, 0x48C9CA4B, 0xCC4D4ECF
 };
+#ifndef FEATURE_CONF_DESC_LENGTH
 static const u32 def_outq_map[OUTQ_PNUM] = {0x1, 0xFE};
+#else
+static const u32 def_outq_map[OUTQ_PNUM] = {0x0, 0xFF};
+#endif
 static const char ptm_drv_name[] = "PTM SL";
 static const char ptm_bond_name[][IFNAMSIZ] = {"PTM US BOND", "PTM DS BOND"};
 
@@ -1005,6 +1009,10 @@ static void us_fp_desq_cfg_ctxt_init(str
 	int i;
 	u32 desc_addr;
 	rx_descriptor_t desc;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	struct tc_priv *tc_priv;
+	tc_priv = priv->tc_priv;
+#endif
 
 	memset(&desq_cfg, 0, sizeof(desq_cfg));
 	/* Initialize US Fast-Path Descriptor Queue Config/Context */
@@ -1012,7 +1020,11 @@ static void us_fp_desq_cfg_ctxt_init(str
 	desq_cfg.fast_path	= 1;
 	desq_cfg.mbox_int_en	= 0;
 	desq_cfg.des_sync_needed = 0;
+#ifndef FEATURE_CONF_DESC_LENGTH
 	desq_cfg.des_num	= __US_FAST_PATH_DES_LIST_NUM;
+#else
+	desq_cfg.des_num	= tc_priv->param.conf_us_fp_desq_len;
+#endif
 	desq_cfg.des_base_addr	= __US_FAST_PATH_DES_LIST_BASE;
 
 	tc_mem_write(priv, fpi_addr(__US_FP_INQ_DES_CFG_CTXT),
@@ -1036,12 +1048,20 @@ static void us_qos_desq_cfg_ctxt_init(st
 	int offset, i;
 	rx_descriptor_t desc;
 	u32 phy_addr;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	struct tc_priv *tc_priv;
+	tc_priv = priv->tc_priv;
+#endif
 
 	/* Setup QoSQ_CFG_CTXT */
 	memset(&qosq_cfg_ctxt, 0, sizeof(qosq_cfg_ctxt));
 
 	qosq_cfg_ctxt.threshold = 8;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	qosq_cfg_ctxt.des_num	= tc_priv->param.conf_us_qos_queue_len;
+#else
 	qosq_cfg_ctxt.des_num	= QOS_DES_NUM / QOSQ_NUM;
+#endif
 
 	offset = 0;
 	for (i = 0; i < QOSQ_NUM; i++) {
@@ -1080,6 +1100,10 @@ static void us_outq_desq_cfg_ctxt_init(s
 	u32 phy_addr;
 	int i;
 	u32 offset;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	struct tc_priv *tc_priv;
+	tc_priv = priv->tc_priv;
+#endif
 
 	/* Setup OUTQ_QoS_CFG_CTXT */
 	/* NOTE: By default, Shaping & WFQ both are DISABLED!! */
@@ -1108,7 +1132,11 @@ static void us_outq_desq_cfg_ctxt_init(s
 	desq_cfg.des_in_own_val	= US_OUTQ_DES_OWN;
 	desq_cfg.mbox_int_en	= 0;
 	desq_cfg.des_sync_needed = 0;
-	desq_cfg.des_num	= 32;
+#ifndef FEATURE_CONF_DESC_LENGTH
+	desq_cfg.des_num	= OUTQ_DESC_PER_Q;
+#else
+	desq_cfg.des_num	= tc_priv->param.conf_us_outq_len;
+#endif
 	/**
 	* Only BC0 is used in VRX518
 	*/
@@ -1174,7 +1202,11 @@ static void us_qos_cfg_init(struct ptm_e
 	/* Set QoS NO DROP */
 	sb_w32(1, __QOSQ_NO_DROP);
 	/* Enable Preemption function/Disable QoS by default */
+#ifdef FEATURE_CONF_DESC_LENGTH
+	sb_w32(0, _CHK_PREEMP_MAP);
+#else
 	sb_w32(1, _CHK_PREEMP_MAP);
+#endif
 	/* By default, all qid mappint to non-preemption queue */
 	sb_w32(0x0, _QID2PREEMP_MAP);
 
@@ -1376,6 +1408,11 @@ static void ptm_local_desq_cfg_ctxt_init
 	u32 dcnt, addr, pdbram_base;
 	unsigned int us_des_alloc[] = {
 		__US_TC_LOCAL_Q0_DES_LIST_NUM, __US_TC_LOCAL_Q1_DES_LIST_NUM};
+#ifdef FEATURE_CONF_DESC_LENGTH
+	struct tc_priv *tc_priv;
+	tc_priv = priv->tc_priv;
+	us_des_alloc[0] = tc_priv->param.conf_us_local_q0_desq_len;
+#endif
 
 	/* Setup the Local DESQ Configuration/Context for UpStream Queues */
 	memset(&desq_cfg, 0, sizeof(desq_cfg));
@@ -2321,6 +2358,10 @@ static void ptm_aca_init(struct ptm_ep_p
 	u32 phybase = priv->ep->phy_membase;
 	u32 start;
 	u32 type;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	struct tc_priv *tc_priv;
+	tc_priv = priv->tc_priv;
+#endif
 
 	priv->tc_priv->tc_ops.soc_cfg_get(&priv->tc_priv->cfg, ptm_id(priv));
 	memset(&param, 0, sizeof(param));
@@ -2334,7 +2375,11 @@ static void ptm_aca_init(struct ptm_ep_p
 #endif
 	txin->hd_size_in_dw = cfg->txin.soc_desc_dwsz;
 	txin->pd_desc_base = SB_XBAR_ADDR(__ACA_TX_IN_PD_LIST_BASE);
+#ifndef FEATURE_CONF_DESC_LENGTH
 	txin->pd_desc_num = __ACA_TX_IN_PD_LIST_NUM;
+#else
+	txin->pd_desc_num = tc_priv->param.conf_us_fp_desq_len;
+#endif
 	txin->pd_size_in_dw = DESC_DWSZ;
 	txin->soc_desc_base = cfg->txin.soc_phydbase;
 	txin->soc_desc_num = cfg->txin.soc_dnum;
--- a/dcdp/tc_main.c
+++ b/dcdp/tc_main.c
@@ -182,6 +182,12 @@ static inline void init_local_param(stru
 	priv->param.txout_dnum = txout_num;
 	priv->param.rxin_dnum = rxin_num;
 	priv->param.rxout_dnum = rxout_num;
+#ifdef FEATURE_CONF_DESC_LENGTH
+	priv->param.conf_us_fp_desq_len = 32;
+	priv->param.conf_us_qos_queue_len = 32;
+	priv->param.conf_us_outq_len = 32;
+	priv->param.conf_us_local_q0_desq_len = 16;
+#endif
 	priv->tc_mode = TC_NONE_MODE;
 	priv->tc_stat = NO_TC;
 
--- a/dcdp/tc_proc.c
+++ b/dcdp/tc_proc.c
@@ -1114,6 +1114,9 @@ static int proc_read_ver(struct seq_file
 		(date >> 16) & 0xff,
 		(date & 0xffff));
 
+#ifdef FEATURE_CONF_DESC_LENGTH
+	seq_puts(seq, " + Support QoS and Configurable descriptor length\n");
+#endif
 #ifdef FEATURE_POWER_DOWN
 	seq_puts(seq, " + Support Power Down enhancement feature\n");
 #endif
@@ -1166,6 +1169,113 @@ static const struct proc_ops tc_soc_proc
 	.proc_release	= single_release,
 };
 
+#ifdef FEATURE_CONF_DESC_LENGTH
+static ssize_t proc_write_desc_conf(struct file *file, const char __user *buf,
+			size_t count, loff_t *data)
+{
+	struct tc_priv *priv;
+	char str[32];
+	int len, rlen, temp;
+	int num, temp_num;
+	char *param_list[20];
+	len = count < sizeof(str) ? count : sizeof(str) - 1;
+	rlen = len - copy_from_user(str, buf, len);
+	str[rlen] = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	priv = (struct tc_priv *)PDE_DATA(file_inode(file));
+	if (priv == NULL)
+		return count;
+
+	num = vrx_split_buffer(str, param_list, ARRAY_SIZE(param_list));
+	if (num < 1 || num > 4)
+		goto proc_dbg_desc_conf;
+
+	temp_num = num;
+	if (num-- != 0) {
+		temp = vrx_atoi(param_list[0]);
+		if (temp < 1 || temp > 128) {
+			pr_info("Fastpath valid range: 1 -> 128\n");
+			goto proc_dbg_desc_conf;
+		}
+	}
+	if (num-- != 0) {
+		temp = vrx_atoi(param_list[1]);
+		if (temp < 1 || temp > 63) {
+			pr_info("QoS valid range: 1 -> 63\n");
+			goto proc_dbg_desc_conf;
+		}
+	}
+	if (num-- != 0) {
+		temp = vrx_atoi(param_list[2]);
+		if (temp < 1 || temp > 128) {
+			pr_info("OutQ valid range: 1 -> 128\n");
+			goto proc_dbg_desc_conf;
+		}
+	}
+	if (num-- != 0) {
+		temp = vrx_atoi(param_list[3]);
+		if (temp < 4 || temp > 16) {
+			pr_info("Local Q0 valid range: 4 -> 16\n");
+			goto proc_dbg_desc_conf;
+		}
+	}
+	num = temp_num;
+	if (num-- != 0) {
+		priv->param.conf_us_fp_desq_len = vrx_atoi(param_list[0]);
+	}
+	if (num-- != 0) {
+		priv->param.conf_us_qos_queue_len = vrx_atoi(param_list[1]);
+	}
+	if (num-- != 0) {
+		priv->param.conf_us_outq_len = vrx_atoi(param_list[2]);
+	}
+	if (num-- != 0) {
+		priv->param.conf_us_local_q0_desq_len = vrx_atoi(param_list[3]);
+	}
+
+	return count;
+
+proc_dbg_desc_conf:
+	pr_info("echo [FP] [QoS] [OutQ] [LocalQ0]> desc_conf\n");
+	return count;
+}
+
+static int proc_read_desc_conf(struct seq_file *seq, void *v)
+{
+	struct tc_priv *priv;
+	priv = (struct tc_priv *)seq->private;
+	if (priv == NULL)
+		return -1;
+	seq_puts(seq, "Upstream descriptor length information:\n");
+	seq_printf(seq, " - Fastpath: %d\n",
+		priv->param.conf_us_fp_desq_len);
+	seq_printf(seq, " - QoS: %d\n",
+		priv->param.conf_us_qos_queue_len);
+	seq_printf(seq, " - OutQ: %d\n",
+		priv->param.conf_us_outq_len);
+	seq_printf(seq, " - Local Q0: %d\n",
+		priv->param.conf_us_local_q0_desq_len);
+	seq_puts(seq, "\n");
+	return 0;
+}
+
+static int proc_read_desc_conf_seq_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, proc_read_desc_conf, PDE_DATA(inode));
+}
+#endif
+
+static const struct proc_ops tc_desc_conf_proc_fops = {
+	.proc_open	= proc_read_desc_conf_seq_open,
+	.proc_read	= seq_read,
+	.proc_write	= proc_write_desc_conf,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+};
+
 static struct tc_proc_list tc_procs[] = {
 	{TC_PROC_DIR,	0,	NULL,			1},
 	{"cfg",		0644, &tc_cfg_proc_fops,	0},
@@ -1174,6 +1284,9 @@ static struct tc_proc_list tc_procs[] =
 	{"showtime",	0200, &tc_show_time_proc_fops,	0},
 	{"ver",		0644, &tc_ver_proc_fops,	0},
 	{"soc",		0644, &tc_soc_proc_fops,	0},
+#ifdef FEATURE_CONF_DESC_LENGTH
+	{"desc_conf",	0644, &tc_desc_conf_proc_fops,	0},
+#endif
 };
 
 int tc_proc_init(struct tc_priv *priv)
@@ -1333,7 +1446,6 @@ proc_ptm_cfg_help:
 	return count;
 }
 
-
 static const struct proc_ops ptm_cfg_proc_fops = {
 	.proc_open = proc_read_cfg_seq_open,
 	.proc_read = seq_read,