gianfar: Use Single-Queue polling for "fsl,etsec2"
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 <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/freescale/gianfar.h b/drivers/net/ethernet/freescale/gianfar.h
index 1aeb34e..84632c5 100644
--- a/drivers/net/ethernet/freescale/gianfar.h
+++ b/drivers/net/ethernet/freescale/gianfar.h
@@ -412,7 +412,9 @@
/* 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
@@ -907,6 +909,22 @@
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
*/
@@ -1016,17 +1034,20 @@
*/
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];
};
@@ -1056,8 +1077,6 @@
* 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;
@@ -1065,6 +1084,7 @@
u16 uses_rxfcb;
u16 padding;
+ u32 device_flags;
/* HW time stamping enabled flag */
int hwts_rx_en;
@@ -1075,10 +1095,11 @@
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 */