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 equal to 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@bootlin.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 dfa6b6d2cfedc8d240f55a04f2ada9fa28c55309..e3cf62253bb96ff245e49730dd4c4b232ce89712 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -135,19 +135,13 @@ 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

-- 
2.50.1