netdev - [PATCH net-next v2 8/9] ice: move prefetch enable to ice_setup_rx

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Message-Id: <20241025-packing-pack-fields-and-ice-implementation-v2-8-734776c88e40@intel.com>
Date: Fri, 25 Oct 2024 17:05:00 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Vladimir Oltean <olteanv@...il.com>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Tony Nguyen <anthony.l.nguyen@...el.com>, 
 Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
 Masahiro Yamada <masahiroy@...nel.org>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
 Jacob Keller <jacob.e.keller@...el.com>
Subject: [PATCH net-next v2 8/9] ice: move prefetch enable to
 ice_setup_rx_ctx

The ice_write_rxq_ctx() function is responsible for programming the Rx
Queue context into hardware. It receives the configuration in unpacked form
via the ice_rlan_ctx structure.

This function unconditionally modifies the context to set the prefetch
enable bit. This was done by commit c31a5c25bb19 ("ice: Always set prefena
when configuring an Rx queue"). Setting this bit makes sense, since
prefetching descriptors is almost always the preferred behavior.

However, the ice_write_rxq_ctx() function is not the place that actually
defines the queue context. We initialize the Rx Queue context in
ice_setup_rx_ctx(). It is surprising to have the Rx queue context changed
by a function who's responsibility is to program the given context to
hardware.

Following the principle of least surprise, move the setting of the prefetch
enable bit out of ice_write_rxq_ctx() and into the ice_setup_rx_ctx().

Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
---
 drivers/net/ethernet/intel/ice/ice_base.c   | 3 +++
 drivers/net/ethernet/intel/ice/ice_common.c | 9 +++------
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_base.c b/drivers/net/ethernet/intel/ice/ice_base.c
index 0a325dec804e..f1fbba19e4e4 100644
--- a/drivers/net/ethernet/intel/ice/ice_base.c
+++ b/drivers/net/ethernet/intel/ice/ice_base.c
@@ -453,6 +453,9 @@ static int ice_setup_rx_ctx(struct ice_rx_ring *ring)
 	/* Rx queue threshold in units of 64 */
 	rlan_ctx.lrxqthresh = 1;
 
+	/* Enable descriptor prefetch */
+	rlan_ctx.prefena = 1;
+
 	/* PF acts as uplink for switchdev; set flex descriptor with src_vsi
 	 * metadata and flags to allow redirecting to PR netdev
 	 */
diff --git a/drivers/net/ethernet/intel/ice/ice_common.c b/drivers/net/ethernet/intel/ice/ice_common.c
index 905f5c745a7b..3cc56b85a480 100644
--- a/drivers/net/ethernet/intel/ice/ice_common.c
+++ b/drivers/net/ethernet/intel/ice/ice_common.c
@@ -1433,14 +1433,13 @@ static void ice_pack_rxq_ctx(const struct ice_rlan_ctx *ctx,
 }
 
 /**
- * ice_write_rxq_ctx
+ * ice_write_rxq_ctx - Write Rx Queue context to hardware
  * @hw: pointer to the hardware structure
  * @rlan_ctx: pointer to the rxq context
  * @rxq_index: the index of the Rx queue
  *
- * Converts rxq context from sparse to dense structure and then writes
- * it to HW register space and enables the hardware to prefetch descriptors
- * instead of only fetching them on demand
+ * Pack the sparse Rx Queue context into dense hardware format and write it
+ * into the HW register space.
  */
 int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 		      u32 rxq_index)
@@ -1450,8 +1449,6 @@ int ice_write_rxq_ctx(struct ice_hw *hw, struct ice_rlan_ctx *rlan_ctx,
 	if (!rlan_ctx)
 		return -EINVAL;
 
-	rlan_ctx->prefena = 1;
-
 	ice_pack_rxq_ctx(rlan_ctx, &buf);
 
 	return ice_copy_rxq_ctx_to_hw(hw, &buf, rxq_index);

-- 
2.47.0.265.g4ca455297942