sfc: Remove configurable FIFO thresholds for pause frame generation

In Falcon we can configure the fill levels of the RX data FIFO which
trigger the generation of pause frames (if enabled), and we have
module parameters for this.

Siena does not allow the levels to be configured (or, if it does, this
is done by the MC firmware and is not configurable by drivers).

So far as I can tell, the module parameters are not used by our
internal scripts and have not been documented (with the exception of
the short parameter descriptions).  Therefore, remove them and always
initialise Falcon with the default values.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/sfc/falcon.c

@@ -1478,36 +1478,26 @@ static void falcon_init_rx_cfg(struct efx_nic *efx)
 	/* RX control FIFO thresholds (32 entries) */
 	const unsigned ctrl_xon_thr = 20;
 	const unsigned ctrl_xoff_thr = 25;
-	/* RX data FIFO thresholds (256-byte units; size varies) */
-	int data_xon_thr = efx_nic_rx_xon_thresh >> 8;
-	int data_xoff_thr = efx_nic_rx_xoff_thresh >> 8;
 	efx_oword_t reg;
 
 	efx_reado(efx, &reg, FR_AZ_RX_CFG);
 	if (efx_nic_rev(efx) <= EFX_REV_FALCON_A1) {
 		/* Data FIFO size is 5.5K */
-		if (data_xon_thr < 0)
-			data_xon_thr = 512 >> 8;
-		if (data_xoff_thr < 0)
-			data_xoff_thr = 2048 >> 8;
 		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_DESC_PUSH_EN, 0);
 		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_USR_BUF_SIZE,
 				    huge_buf_size);
-		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XON_MAC_TH, data_xon_thr);
-		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XOFF_MAC_TH, data_xoff_thr);
+		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XON_MAC_TH, 512 >> 8);
+		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XOFF_MAC_TH, 2048 >> 8);
 		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XON_TX_TH, ctrl_xon_thr);
 		EFX_SET_OWORD_FIELD(reg, FRF_AA_RX_XOFF_TX_TH, ctrl_xoff_thr);
 	} else {
 		/* Data FIFO size is 80K; register fields moved */
-		if (data_xon_thr < 0)
-			data_xon_thr = 27648 >> 8; /* ~3*max MTU */
-		if (data_xoff_thr < 0)
-			data_xoff_thr = 54272 >> 8; /* ~80Kb - 3*max MTU */
 		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_DESC_PUSH_EN, 0);
 		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_USR_BUF_SIZE,
 				    huge_buf_size);
-		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XON_MAC_TH, data_xon_thr);
-		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XOFF_MAC_TH, data_xoff_thr);
+		/* Send XON and XOFF at ~3 * max MTU away from empty/full */
+		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XON_MAC_TH, 27648 >> 8);
+		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XOFF_MAC_TH, 54272 >> 8);
 		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XON_TX_TH, ctrl_xon_thr);
 		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_XOFF_TX_TH, ctrl_xoff_thr);
 		EFX_SET_OWORD_FIELD(reg, FRF_BZ_RX_INGR_EN, 1);

drivers/net/sfc/nic.c

@@ -41,26 +41,6 @@
 #define RX_DC_ENTRIES 64
 #define RX_DC_ENTRIES_ORDER 3
 
-/* RX FIFO XOFF watermark
- *
- * When the amount of the RX FIFO increases used increases past this
- * watermark send XOFF. Only used if RX flow control is enabled (ethtool -A)
- * This also has an effect on RX/TX arbitration
- */
-int efx_nic_rx_xoff_thresh = -1;
-module_param_named(rx_xoff_thresh_bytes, efx_nic_rx_xoff_thresh, int, 0644);
-MODULE_PARM_DESC(rx_xoff_thresh_bytes, "RX fifo XOFF threshold");
-
-/* RX FIFO XON watermark
- *
- * When the amount of the RX FIFO used decreases below this
- * watermark send XON. Only used if TX flow control is enabled (ethtool -A)
- * This also has an effect on RX/TX arbitration
- */
-int efx_nic_rx_xon_thresh = -1;
-module_param_named(rx_xon_thresh_bytes, efx_nic_rx_xon_thresh, int, 0644);
-MODULE_PARM_DESC(rx_xon_thresh_bytes, "RX fifo XON threshold");
-
 /* If EFX_MAX_INT_ERRORS internal errors occur within
  * EFX_INT_ERROR_EXPIRE seconds, we consider the NIC broken and
  * disable it.

drivers/net/sfc/nic.h

@@ -188,7 +188,6 @@ extern void efx_nic_eventq_read_ack(struct efx_channel *channel);
 /* MAC/PHY */
 extern void falcon_drain_tx_fifo(struct efx_nic *efx);
 extern void falcon_reconfigure_mac_wrapper(struct efx_nic *efx);
-extern int efx_nic_rx_xoff_thresh, efx_nic_rx_xon_thresh;
 
 /* Interrupts and test events */
 extern int efx_nic_init_interrupt(struct efx_nic *efx);

drivers/net/sfc/siena.c

@@ -341,11 +341,6 @@ static int siena_init_nic(struct efx_nic *efx)
 	       FRF_CZ_RX_RSS_IPV6_TKEY_HI_WIDTH / 8);
 	efx_writeo(efx, &temp, FR_CZ_RX_RSS_IPV6_REG3);
 
-	if (efx_nic_rx_xoff_thresh >= 0 || efx_nic_rx_xon_thresh >= 0)
-		/* No MCDI operation has been defined to set thresholds */
-		netif_err(efx, hw, efx->net_dev,
-			  "ignoring RX flow control thresholds\n");
-
 	/* Enable event logging */
 	rc = efx_mcdi_log_ctrl(efx, true, false, 0);
 	if (rc)