netdev - [PATCH net-next v3 3/4] net: airoha: Add the capability to allocate hwfd buffers via reserved-memory

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Message-Id: <20250521-airopha-desc-sram-v3-3-a6e9b085b4f0@kernel.org>
Date: Wed, 21 May 2025 09:16:38 +0200
From: Lorenzo Bianconi <lorenzo@...nel.org>
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>, Lorenzo Bianconi <lorenzo@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, 
 linux-mediatek@...ts.infradead.org, netdev@...r.kernel.org, 
 devicetree@...r.kernel.org
Subject: [PATCH net-next v3 3/4] net: airoha: Add the capability to
 allocate hwfd buffers via reserved-memory

In some configurations QDMA blocks require a contiguous block of
system memory for hwfd buffers queue. Introduce the capability to allocate
hw buffers forwarding queue via the reserved-memory DTS property instead of
running dmam_alloc_coherent().

Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 33 +++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 5f7cbbcbb1d469836dfcea95137c960bfd076744..20e590d76735e72a1a538a42d2a1f49b882deccc 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -5,6 +5,7 @@
  */
 #include <linux/of.h>
 #include <linux/of_net.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/platform_device.h>
 #include <linux/tcp.h>
 #include <linux/u64_stats_sync.h>
@@ -1076,9 +1077,11 @@ static void airoha_qdma_cleanup_tx_queue(struct airoha_queue *q)
 static int airoha_qdma_init_hfwd_queues(struct airoha_qdma *qdma)
 {
 	struct airoha_eth *eth = qdma->eth;
+	int id = qdma - &eth->qdma[0];
 	dma_addr_t dma_addr;
+	const char *name;
+	int size, index;
 	u32 status;
-	int size;

 	size = HW_DSCP_NUM * sizeof(struct airoha_qdma_fwd_desc);
 	if (!dmam_alloc_coherent(eth->dev, size, &dma_addr, GFP_KERNEL))
@@ -1086,10 +1089,34 @@ static int airoha_qdma_init_hfwd_queues(struct airoha_qdma *qdma)

 	airoha_qdma_wr(qdma, REG_FWD_DSCP_BASE, dma_addr);

-	size = AIROHA_MAX_PACKET_SIZE * HW_DSCP_NUM;
-	if (!dmam_alloc_coherent(eth->dev, size, &dma_addr, GFP_KERNEL))
+	name = devm_kasprintf(eth->dev, GFP_KERNEL, "qdma%d-buf", id);
+	if (!name)
 		return -ENOMEM;

+	index = of_property_match_string(eth->dev->of_node,
+					 "memory-region-names", name);
+	if (index >= 0) {
+		struct reserved_mem *rmem;
+		struct device_node *np;
+
+		/* Consume reserved memory for hw forwarding buffers queue if
+		 * available in the DTS
+		 */
+		np = of_parse_phandle(eth->dev->of_node, "memory-region",
+				      index);
+		if (!np)
+			return -ENODEV;
+
+		rmem = of_reserved_mem_lookup(np);
+		of_node_put(np);
+		dma_addr = rmem->base;
+	} else {
+		size = AIROHA_MAX_PACKET_SIZE * HW_DSCP_NUM;
+		if (!dmam_alloc_coherent(eth->dev, size, &dma_addr,
+					 GFP_KERNEL))
+			return -ENOMEM;
+	}
+
 	airoha_qdma_wr(qdma, REG_FWD_BUF_BASE, dma_addr);

 	airoha_qdma_rmw(qdma, REG_HW_FWD_DSCP_CFG,

-- 
2.49.0