linux-kernel - [PATCH net-next 07/15] net: macb: simplify macb_adj_dma_desc

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Message-Id: <20251014-macb-cleanup-v1-7-31cd266e22cd@bootlin.com>
Date: Tue, 14 Oct 2025 17:25:08 +0200
From: Théo Lebrun <theo.lebrun@...tlin.com>
To: Andrew Lunn <andrew+netdev@...n.ch>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>, 
 Richard Cochran <richardcochran@...il.com>, 
 Russell King <linux@...linux.org.uk>
Cc: netdev@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>, 
 Tawfik Bayouk <tawfik.bayouk@...ileye.com>, 
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Grégory Clement <gregory.clement@...tlin.com>, 
 Benoît Monin <benoit.monin@...tlin.com>, 
 Maxime Chevallier <maxime.chevallier@...tlin.com>, 
 Théo Lebrun <theo.lebrun@...tlin.com>
Subject: [PATCH net-next 07/15] net: macb: simplify macb_adj_dma_desc_idx()

The function body uses a switch statement on bp->hw_dma_cap and handles
its four possible values: 0, is_64b, is_ptp, is_64b && is_ptp.

Instead, refactor by noticing that the return value is:
   desc_size * MULT
with MULT = 3 if is_64b && is_ptp,
            2 if is_64b || is_ptp,
            1 otherwise.

MULT can be expressed as:
   1 + is_64b + is_ptp

Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
---
 drivers/net/ethernet/cadence/macb_main.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 7f74e280a3351ee7f961ff5ecd9550470b2e68eb..44a411662786ca4f309d6f9389b0d36819fc40ad 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -136,19 +136,13 @@ static unsigned int macb_dma_desc_get_size(struct macb *bp)
 static unsigned int macb_adj_dma_desc_idx(struct macb *bp, unsigned int desc_idx)
 {
 #ifdef MACB_EXT_DESC
-	switch (bp->hw_dma_cap) {
-	case HW_DMA_CAP_64B:
-	case HW_DMA_CAP_PTP:
-		desc_idx <<= 1;
-		break;
-	case HW_DMA_CAP_64B_PTP:
-		desc_idx *= 3;
-		break;
-	default:
-		break;
-	}
-#endif
+	bool is_ptp = bp->hw_dma_cap & HW_DMA_CAP_PTP;
+	bool is_64b = bp->hw_dma_cap & HW_DMA_CAP_64B;
+
+	return desc_idx * (1 + is_64b + is_ptp);
+#else
 	return desc_idx;
+#endif
 }

 #ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT

-- 
2.51.0