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gianfar: Use Single-Queue polling for "fsl,etsec2"
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For the "fsl,etsec2" compatible models the driver currently
supports 8 Tx and Rx DMA rings (aka HW queues).  However, there
are only 2 pairs of Rx/Tx interrupt lines, as these controllers
are integrated in low power SoCs with 2 CPUs at most.  As a result,
there are at most 2 NAPI instances that have to service multiple
Tx and Rx queues for these devices.  This complicates the NAPI
polling routine having to iterate over the mutiple Rx/Tx queues
hooked to the same interrupt lines.  And there's also an overhead
at HW level, as the controller needs to service all the 8 Tx rings
in a round robin manner.  The combined overhead shows up for multi
parallel Tx flows transmitted by the kernel stack, when the driver
usually starts returning NETDEV_TX_BUSY leading to NETDEV WATCHDOG
Tx timeout triggering if the Tx path is congested for too long.

As an alternative, this patch makes the driver support only one
Tx/Rx DMA ring per NAPI instance (per interrupt group or pair
of Tx/Rx interrupt lines) by default.  The simplified single queue
polling routine (gfar_poll_sq) will be the default napi poll routine
for the etsec2 devices too.  Some adjustments needed to be made to
link the Tx/Rx HW queues with each NAPI instance (2 in this case).
The gfar_poll_sq() is already successfully used by older SQ_SG_MODE
(single interrupt group) controllers.
This patch fixes Tx timeout triggering under heavy Tx traffic load
(i.e. iperf -c -P 8) for the "fsl,etsec2" (currently the only
MQ_MG_MODE devices).  There's also a significant memory footprint
reduction by supporting 2 Rx/Tx DMA rings (at most), instead of 8,
for these devices.

Signed-off-by: Claudiu Manoil <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@claudiu-m @davem330
claudiu-m authored and davem330 committed Mar 10, 2014
1 parent aeb12c5 commit 71ff9e3
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Showing 2 changed files with 79 additions and 32 deletions.
70 changes: 48 additions & 22 deletions drivers/net/ethernet/freescale/gianfar.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -363,7 +363,10 @@ static void gfar_mac_rx_config(struct gfar_private *priv)
if (priv->rx_filer_enable) {
rctrl |= RCTRL_FILREN;
/* Program the RIR0 reg with the required distribution */
gfar_write(&regs->rir0, DEFAULT_RIR0);
if (priv->poll_mode == GFAR_SQ_POLLING)
gfar_write(&regs->rir0, DEFAULT_2RXQ_RIR0);
else /* GFAR_MQ_POLLING */
gfar_write(&regs->rir0, DEFAULT_8RXQ_RIR0);
}

/* Restore PROMISC mode */
Expand Down Expand Up @@ -636,7 +639,6 @@ static int gfar_parse_group(struct device_node *np,
struct gfar_private *priv, const char *model)
{
struct gfar_priv_grp *grp = &priv->gfargrp[priv->num_grps];
u32 *queue_mask;
int i;

for (i = 0; i < GFAR_NUM_IRQS; i++) {
Expand Down Expand Up @@ -665,12 +667,20 @@ static int gfar_parse_group(struct device_node *np,
grp->priv = priv;
spin_lock_init(&grp->grplock);
if (priv->mode == MQ_MG_MODE) {
queue_mask = (u32 *)of_get_property(np, "fsl,rx-bit-map", NULL);
grp->rx_bit_map = queue_mask ?
*queue_mask : (DEFAULT_MAPPING >> priv->num_grps);
queue_mask = (u32 *)of_get_property(np, "fsl,tx-bit-map", NULL);
grp->tx_bit_map = queue_mask ?
*queue_mask : (DEFAULT_MAPPING >> priv->num_grps);
u32 *rxq_mask, *txq_mask;
rxq_mask = (u32 *)of_get_property(np, "fsl,rx-bit-map", NULL);
txq_mask = (u32 *)of_get_property(np, "fsl,tx-bit-map", NULL);

if (priv->poll_mode == GFAR_SQ_POLLING) {
/* One Q per interrupt group: Q0 to G0, Q1 to G1 */
grp->rx_bit_map = (DEFAULT_MAPPING >> priv->num_grps);
grp->tx_bit_map = (DEFAULT_MAPPING >> priv->num_grps);
} else { /* GFAR_MQ_POLLING */
grp->rx_bit_map = rxq_mask ?
*rxq_mask : (DEFAULT_MAPPING >> priv->num_grps);
grp->tx_bit_map = txq_mask ?
*txq_mask : (DEFAULT_MAPPING >> priv->num_grps);
}
} else {
grp->rx_bit_map = 0xFF;
grp->tx_bit_map = 0xFF;
Expand All @@ -686,13 +696,17 @@ static int gfar_parse_group(struct device_node *np,
* also assign queues to groups
*/
for_each_set_bit(i, &grp->rx_bit_map, priv->num_rx_queues) {
if (!grp->rx_queue)
grp->rx_queue = priv->rx_queue[i];
grp->num_rx_queues++;
grp->rstat |= (RSTAT_CLEAR_RHALT >> i);
priv->rqueue |= ((RQUEUE_EN0 | RQUEUE_EX0) >> i);
priv->rx_queue[i]->grp = grp;
}

for_each_set_bit(i, &grp->tx_bit_map, priv->num_tx_queues) {
if (!grp->tx_queue)
grp->tx_queue = priv->tx_queue[i];
grp->num_tx_queues++;
grp->tstat |= (TSTAT_CLEAR_THALT >> i);
priv->tqueue |= (TQUEUE_EN0 >> i);
Expand Down Expand Up @@ -723,9 +737,22 @@ static int gfar_of_init(struct platform_device *ofdev, struct net_device **pdev)
if (!np || !of_device_is_available(np))
return -ENODEV;

/* parse the num of tx and rx queues */
/* parse the num of HW tx and rx queues */
tx_queues = (u32 *)of_get_property(np, "fsl,num_tx_queues", NULL);
num_tx_qs = tx_queues ? *tx_queues : 1;
rx_queues = (u32 *)of_get_property(np, "fsl,num_rx_queues", NULL);

if (priv->mode == SQ_SG_MODE) {
num_tx_qs = 1;
num_rx_qs = 1;
} else { /* MQ_MG_MODE */
if (priv->poll_mode == GFAR_SQ_POLLING) {
num_tx_qs = 2; /* one q per int group */
num_rx_qs = 2; /* one q per int group */
} else { /* GFAR_MQ_POLLING */
num_tx_qs = tx_queues ? *tx_queues : 1;
num_rx_qs = rx_queues ? *rx_queues : 1;
}
}

if (num_tx_qs > MAX_TX_QS) {
pr_err("num_tx_qs(=%d) greater than MAX_TX_QS(=%d)\n",
Expand All @@ -734,9 +761,6 @@ static int gfar_of_init(struct platform_device *ofdev, struct net_device **pdev)
return -EINVAL;
}

rx_queues = (u32 *)of_get_property(np, "fsl,num_rx_queues", NULL);
num_rx_qs = rx_queues ? *rx_queues : 1;

if (num_rx_qs > MAX_RX_QS) {
pr_err("num_rx_qs(=%d) greater than MAX_RX_QS(=%d)\n",
num_rx_qs, MAX_RX_QS);
Expand Down Expand Up @@ -777,13 +801,15 @@ static int gfar_of_init(struct platform_device *ofdev, struct net_device **pdev)
/* Parse and initialize group specific information */
if (of_device_is_compatible(np, "fsl,etsec2")) {
priv->mode = MQ_MG_MODE;
priv->poll_mode = GFAR_SQ_POLLING;
for_each_child_of_node(np, child) {
err = gfar_parse_group(child, priv, model);
if (err)
goto err_grp_init;
}
} else {
priv->mode = SQ_SG_MODE;
priv->poll_mode = GFAR_SQ_POLLING;
err = gfar_parse_group(np, priv, model);
if (err)
goto err_grp_init;
Expand Down Expand Up @@ -1263,13 +1289,13 @@ static int gfar_probe(struct platform_device *ofdev)
dev->ethtool_ops = &gfar_ethtool_ops;

/* Register for napi ...We are registering NAPI for each grp */
if (priv->mode == SQ_SG_MODE) {
netif_napi_add(dev, &priv->gfargrp[0].napi_rx, gfar_poll_rx_sq,
GFAR_DEV_WEIGHT);
netif_napi_add(dev, &priv->gfargrp[0].napi_tx, gfar_poll_tx_sq,
2);
} else {
for (i = 0; i < priv->num_grps; i++) {
for (i = 0; i < priv->num_grps; i++) {
if (priv->poll_mode == GFAR_SQ_POLLING) {
netif_napi_add(dev, &priv->gfargrp[i].napi_rx,
gfar_poll_rx_sq, GFAR_DEV_WEIGHT);
netif_napi_add(dev, &priv->gfargrp[i].napi_tx,
gfar_poll_tx_sq, 2);
} else {
netif_napi_add(dev, &priv->gfargrp[i].napi_rx,
gfar_poll_rx, GFAR_DEV_WEIGHT);
netif_napi_add(dev, &priv->gfargrp[i].napi_tx,
Expand Down Expand Up @@ -2819,7 +2845,7 @@ static int gfar_poll_rx_sq(struct napi_struct *napi, int budget)
struct gfar_priv_grp *gfargrp =
container_of(napi, struct gfar_priv_grp, napi_rx);
struct gfar __iomem *regs = gfargrp->regs;
struct gfar_priv_rx_q *rx_queue = gfargrp->priv->rx_queue[0];
struct gfar_priv_rx_q *rx_queue = gfargrp->rx_queue;
int work_done = 0;

/* Clear IEVENT, so interrupts aren't called again
Expand Down Expand Up @@ -2850,7 +2876,7 @@ static int gfar_poll_tx_sq(struct napi_struct *napi, int budget)
struct gfar_priv_grp *gfargrp =
container_of(napi, struct gfar_priv_grp, napi_tx);
struct gfar __iomem *regs = gfargrp->regs;
struct gfar_priv_tx_q *tx_queue = gfargrp->priv->tx_queue[0];
struct gfar_priv_tx_q *tx_queue = gfargrp->tx_queue;
u32 imask;

/* Clear IEVENT, so interrupts aren't called again
Expand Down
41 changes: 31 additions & 10 deletions drivers/net/ethernet/freescale/gianfar.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -412,7 +412,9 @@ extern const char gfar_driver_version[];

/* This default RIR value directly corresponds
* to the 3-bit hash value generated */
#define DEFAULT_RIR0 0x05397700
#define DEFAULT_8RXQ_RIR0 0x05397700
/* Map even hash values to Q0, and odd ones to Q1 */
#define DEFAULT_2RXQ_RIR0 0x04104100

/* RQFCR register bits */
#define RQFCR_GPI 0x80000000
Expand Down Expand Up @@ -907,6 +909,22 @@ enum {
MQ_MG_MODE
};

/* GFAR_SQ_POLLING: Single Queue NAPI polling mode
* The driver supports a single pair of RX/Tx queues
* per interrupt group (Rx/Tx int line). MQ_MG mode
* devices have 2 interrupt groups, so the device will
* have a total of 2 Tx and 2 Rx queues in this case.
* GFAR_MQ_POLLING: Multi Queue NAPI polling mode
* The driver supports all the 8 Rx and Tx HW queues
* each queue mapped by the Device Tree to one of
* the 2 interrupt groups. This mode implies significant
* processing overhead (CPU and controller level).
*/
enum gfar_poll_mode {
GFAR_SQ_POLLING = 0,
GFAR_MQ_POLLING
};

/*
* Per TX queue stats
*/
Expand Down Expand Up @@ -1016,17 +1034,20 @@ struct gfar_irqinfo {
*/

struct gfar_priv_grp {
spinlock_t grplock __attribute__ ((aligned (SMP_CACHE_BYTES)));
spinlock_t grplock __aligned(SMP_CACHE_BYTES);
struct napi_struct napi_rx;
struct napi_struct napi_tx;
struct gfar_private *priv;
struct gfar __iomem *regs;
unsigned int rstat;
unsigned long num_rx_queues;
unsigned long rx_bit_map;
struct gfar_priv_tx_q *tx_queue;
struct gfar_priv_rx_q *rx_queue;
unsigned int tstat;
unsigned int rstat;

struct gfar_private *priv;
unsigned long num_tx_queues;
unsigned long tx_bit_map;
unsigned long num_rx_queues;
unsigned long rx_bit_map;

struct gfar_irqinfo *irqinfo[GFAR_NUM_IRQS];
};
Expand Down Expand Up @@ -1056,15 +1077,14 @@ enum gfar_dev_state {
* the buffer descriptor determines the actual condition.
*/
struct gfar_private {
unsigned int num_rx_queues;

struct device *dev;
struct net_device *ndev;
enum gfar_errata errata;
unsigned int rx_buffer_size;

u16 uses_rxfcb;
u16 padding;
u32 device_flags;

/* HW time stamping enabled flag */
int hwts_rx_en;
Expand All @@ -1075,10 +1095,11 @@ struct gfar_private {
struct gfar_priv_grp gfargrp[MAXGROUPS];

unsigned long state;
u32 device_flags;

unsigned int mode;
unsigned short mode;
unsigned short poll_mode;
unsigned int num_tx_queues;
unsigned int num_rx_queues;
unsigned int num_grps;

/* Network Statistics */
Expand Down

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