[PATCH net-next v3 3/6] net: xilinx: axienet: Combine CR calculation

[Sean Anderson <sean.anderson@linux.dev>]

Combine the common parts of the CR calculations for better code reuse.
While we're at it, simplify the code a bit.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

Changes in v3:
- Fix mismatched parameter name documentation for axienet_calc_cr
- Integrate some cleanups originally included in
  https://lore.kernel.org/netdev/20240909230908.1319982-1-sean.anderson@linux.dev/

Changes in v2:
- Split off from runtime coalesce modification support

 drivers/net/ethernet/xilinx/xilinx_axienet.h  |  3 -
 .../net/ethernet/xilinx/xilinx_axienet_main.c | 64 ++++++++++---------
 2 files changed, 34 insertions(+), 33 deletions(-)

diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
index a3f4f3e42587..8fd3b45ef6aa 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
@@ -112,9 +112,6 @@
 #define XAXIDMA_DELAY_MASK		0xFF000000 /* Delay timeout counter */
 #define XAXIDMA_COALESCE_MASK		0x00FF0000 /* Coalesce counter */
 
-#define XAXIDMA_DELAY_SHIFT		24
-#define XAXIDMA_COALESCE_SHIFT		16
-
 #define XAXIDMA_IRQ_IOC_MASK		0x00001000 /* Completion intr */
 #define XAXIDMA_IRQ_DELAY_MASK		0x00002000 /* Delay interrupt */
 #define XAXIDMA_IRQ_ERROR_MASK		0x00004000 /* Error interrupt */
diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
index ccc4a1620015..961c9c9e5e18 100644
--- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
+++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
@@ -224,22 +224,40 @@ static void axienet_dma_bd_release(struct net_device *ndev)
 }
 
 /**
- * axienet_usec_to_timer - Calculate IRQ delay timer value
- * @lp:		Pointer to the axienet_local structure
- * @coalesce_usec: Microseconds to convert into timer value
+ * axienet_calc_cr() - Calculate control register value
+ * @lp: Device private data
+ * @count: Number of completions before an interrupt
+ * @usec: Microseconds after the last completion before an interrupt
+ *
+ * Calculate a control register value based on the coalescing settings. The
+ * run/stop bit is not set.
  */
-static u32 axienet_usec_to_timer(struct axienet_local *lp, u32 coalesce_usec)
+static u32 axienet_calc_cr(struct axienet_local *lp, u32 count, u32 usec)
 {
-	u32 result;
-	u64 clk_rate = 125000000; /* arbitrary guess if no clock rate set */
+	u32 cr;
 
-	if (lp->axi_clk)
-		clk_rate = clk_get_rate(lp->axi_clk);
+	cr = FIELD_PREP(XAXIDMA_COALESCE_MASK, count) | XAXIDMA_IRQ_IOC_MASK |
+	     XAXIDMA_IRQ_ERROR_MASK;
+	/* Only set interrupt delay timer if not generating an interrupt on
+	 * the first packet. Otherwise leave at 0 to disable delay interrupt.
+	 */
+	if (count > 1) {
+		u64 clk_rate = 125000000; /* arbitrary guess if no clock rate set */
+		u32 timer;
 
-	/* 1 Timeout Interval = 125 * (clock period of SG clock) */
-	result = DIV64_U64_ROUND_CLOSEST((u64)coalesce_usec * clk_rate,
-					 XAXIDMA_DELAY_SCALE);
-	return min(result, FIELD_MAX(XAXIDMA_DELAY_MASK));
+		if (lp->axi_clk)
+			clk_rate = clk_get_rate(lp->axi_clk);
+
+		/* 1 Timeout Interval = 125 * (clock period of SG clock) */
+		timer = DIV64_U64_ROUND_CLOSEST((u64)usec * clk_rate,
+						XAXIDMA_DELAY_SCALE);
+
+		timer = min(timer, FIELD_MAX(XAXIDMA_DELAY_MASK));
+		cr |= FIELD_PREP(XAXIDMA_DELAY_MASK, timer) |
+		      XAXIDMA_IRQ_DELAY_MASK;
+	}
+
+	return cr;
 }
 
 /**
@@ -249,27 +267,13 @@ static u32 axienet_usec_to_timer(struct axienet_local *lp, u32 coalesce_usec)
 static void axienet_dma_start(struct axienet_local *lp)
 {
 	/* Start updating the Rx channel control register */
-	lp->rx_dma_cr = (lp->coalesce_count_rx << XAXIDMA_COALESCE_SHIFT) |
-			XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_ERROR_MASK;
-	/* Only set interrupt delay timer if not generating an interrupt on
-	 * the first RX packet. Otherwise leave at 0 to disable delay interrupt.
-	 */
-	if (lp->coalesce_count_rx > 1)
-		lp->rx_dma_cr |= (axienet_usec_to_timer(lp, lp->coalesce_usec_rx)
-					<< XAXIDMA_DELAY_SHIFT) |
-				 XAXIDMA_IRQ_DELAY_MASK;
+	lp->rx_dma_cr = axienet_calc_cr(lp, lp->coalesce_count_rx,
+					lp->coalesce_usec_rx);
 	axienet_dma_out32(lp, XAXIDMA_RX_CR_OFFSET, lp->rx_dma_cr);
 
 	/* Start updating the Tx channel control register */
-	lp->tx_dma_cr = (lp->coalesce_count_tx << XAXIDMA_COALESCE_SHIFT) |
-			XAXIDMA_IRQ_IOC_MASK | XAXIDMA_IRQ_ERROR_MASK;
-	/* Only set interrupt delay timer if not generating an interrupt on
-	 * the first TX packet. Otherwise leave at 0 to disable delay interrupt.
-	 */
-	if (lp->coalesce_count_tx > 1)
-		lp->tx_dma_cr |= (axienet_usec_to_timer(lp, lp->coalesce_usec_tx)
-					<< XAXIDMA_DELAY_SHIFT) |
-				 XAXIDMA_IRQ_DELAY_MASK;
+	lp->tx_dma_cr = axienet_calc_cr(lp, lp->coalesce_count_tx,
+					lp->coalesce_usec_tx);
 	axienet_dma_out32(lp, XAXIDMA_TX_CR_OFFSET, lp->tx_dma_cr);
 
 	/* Populate the tail pointer and bring the Rx Axi DMA engine out of
-- 
2.35.1.1320.gc452695387.dirty