[PATCH v3 3/3] staging/rdma/hfi1: Method to toggle "fast ECN" detection

[ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org]

From: Vennila Megavannan <vennila.megavannan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

Add a module paramter to toggle prescan/Fast ECN Detection and remove the
Kconfig option which used to control this.

Reviewed-by: Arthur Kepner<arthur.kepner-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Reviewed-by: Mike Marciniszyn<mike.marciniszyn-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Vennila Megavannan<vennila.megavannan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Ira Weiny <ira.weiny-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

---
Changes from V1:
	Redo commit message as well as Kconfig help to make it clear what the
	compile and module options do.

Changes from V2:
	Remove Kconfig option completely

 drivers/staging/rdma/hfi1/Kconfig  | 10 ----------
 drivers/staging/rdma/hfi1/driver.c | 24 ++++++++++++++----------
 2 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/staging/rdma/hfi1/Kconfig b/drivers/staging/rdma/hfi1/Kconfig
index fd25078ee923..0ad92fdb3fe6 100644
--- a/drivers/staging/rdma/hfi1/Kconfig
+++ b/drivers/staging/rdma/hfi1/Kconfig
@@ -25,13 +25,3 @@ config SDMA_VERBOSITY
 	---help---
 	This is a configuration flag to enable verbose
 	SDMA debug
-config PRESCAN_RXQ
-	bool "Enable prescanning of the RX queue for ECNs"
-	depends on INFINIBAND_HFI1
-	default n
-	---help---
-	This option toggles the prescanning of the receive queue for
-	Explicit Congestion Notifications. If an ECN is detected, it
-	is processed as quickly as possible, the ECN is toggled off.
-	After the prescanning step, the receive queue is processed as
-	usual.
diff --git a/drivers/staging/rdma/hfi1/driver.c b/drivers/staging/rdma/hfi1/driver.c
index 9a4ec09af020..145ac3061f5d 100644
--- a/drivers/staging/rdma/hfi1/driver.c
+++ b/drivers/staging/rdma/hfi1/driver.c
@@ -83,6 +83,12 @@ unsigned int hfi1_cu = 1;
 module_param_named(cu, hfi1_cu, uint, S_IRUGO);
 MODULE_PARM_DESC(cu, "Credit return units");
 
+static unsigned int prescan_rx_queue;
+module_param_named(prescan_rxq, prescan_rx_queue, uint,
+		   S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(prescan_rxq,
+		 "Used to toggle rx prescan. Set to 1 to enable prescan");
+
 unsigned long hfi1_cap_mask = HFI1_CAP_MASK_DEFAULT;
 static int hfi1_caps_set(const char *, const struct kernel_param *);
 static int hfi1_caps_get(char *, const struct kernel_param *);
@@ -434,11 +440,6 @@ static inline void init_packet(struct hfi1_ctxtdata *rcd,
 	packet->rcv_flags = 0;
 }
 
-#ifndef CONFIG_PRESCAN_RXQ
-static void prescan_rxq(struct hfi1_packet *packet) {}
-#else /* !CONFIG_PRESCAN_RXQ */
-static int prescan_receive_queue;
-
 static void process_ecn(struct hfi1_qp *qp, struct hfi1_ib_header *hdr,
 			struct hfi1_other_headers *ohdr,
 			u64 rhf, u32 bth1, struct ib_grh *grh)
@@ -541,15 +542,19 @@ static inline void update_ps_mdata(struct ps_mdata *mdata)
  * containing Excplicit Congestion Notifications (FECNs, or BECNs).
  * When an ECN is found, process the Congestion Notification, and toggle
  * it off.
+ * This is declared as a macro to allow quick checking of the module param and
+ * avoid the overhead of a function call if not enabled.
  */
-static void prescan_rxq(struct hfi1_packet *packet)
+#define prescan_rxq(packet) \
+	do { \
+		if (prescan_rx_queue) \
+			__prescan_rxq(packet); \
+	} while (0)
+static void __prescan_rxq(struct hfi1_packet *packet)
 {
 	struct hfi1_ctxtdata *rcd = packet->rcd;
 	struct ps_mdata mdata;
 
-	if (!prescan_receive_queue)
-		return;
-
 	init_ps_mdata(&mdata, packet);
 
 	while (1) {
@@ -609,7 +614,6 @@ next:
 		update_ps_mdata(&mdata);
 	}
 }
-#endif /* CONFIG_PRESCAN_RXQ */
 
 static inline int process_rcv_packet(struct hfi1_packet *packet, int thread)
 {
-- 
1.8.2

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