linux-kernel - [PATCH net-next v3 1/2] net: ravb: Make DBAT entry count configurable per-SoC

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Message-ID: <20251023112111.215198-2-prabhakar.mahadev-lad.rj@bp.renesas.com>
Date: Thu, 23 Oct 2025 12:21:10 +0100
From: Prabhakar <prabhakar.csengg@...il.com>
To: Niklas Söderlund <niklas.soderlund@...natech.se>,
	Paul Barker <paul@...rker.dev>,
	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>
Cc: netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Prabhakar <prabhakar.csengg@...il.com>,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Subject: [PATCH net-next v3 1/2] net: ravb: Make DBAT entry count configurable per-SoC

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Avoid wasting coherent DMA memory by allocating the descriptor base
address table sized for the actual number of DBAT/CDARq entries supported
by the SoC. Some platforms (for example GBETH) only provide two CDARq
entries; previously the driver always allocated space for 22 entries which
needlessly consumed memory on those systems.

Pass the per-SoC dbat_entry_num via struct ravb_hw_info and use it for
allocation and initialization in probe. This sizes the table correctly and
removes the unnecessary memory overhead on SoCs with fewer DBAT entries.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
---
v2->v3:
- Reworded commit message for clarity.

v1->v2:
- Added Reviewed-by tag from Niklas.
---
 drivers/net/ethernet/renesas/ravb.h      | 2 +-
 drivers/net/ethernet/renesas/ravb_main.c | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 7b48060c250b..d65cd83ddd16 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -1017,7 +1017,6 @@ enum CSR2_BIT {
 #define CSR2_CSUM_ENABLE (CSR2_RTCP4 | CSR2_RUDP4 | CSR2_RICMP4 | \
 			  CSR2_RTCP6 | CSR2_RUDP6 | CSR2_RICMP6)
 
-#define DBAT_ENTRY_NUM	22
 #define RX_QUEUE_OFFSET	4
 #define NUM_RX_QUEUE	2
 #define NUM_TX_QUEUE	2
@@ -1062,6 +1061,7 @@ struct ravb_hw_info {
 	u32 rx_max_frame_size;
 	u32 rx_buffer_size;
 	u32 rx_desc_size;
+	u32 dbat_entry_num;
 	unsigned aligned_tx: 1;
 	unsigned coalesce_irqs:1;	/* Needs software IRQ coalescing */
 
diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index 9d3bd65b85ff..69d382e8757d 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -2694,6 +2694,7 @@ static const struct ravb_hw_info ravb_gen2_hw_info = {
 	.rx_buffer_size = SZ_2K +
 			  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
 	.rx_desc_size = sizeof(struct ravb_ex_rx_desc),
+	.dbat_entry_num = 22,
 	.aligned_tx = 1,
 	.gptp = 1,
 	.nc_queues = 1,
@@ -2717,6 +2718,7 @@ static const struct ravb_hw_info ravb_gen3_hw_info = {
 	.rx_buffer_size = SZ_2K +
 			  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
 	.rx_desc_size = sizeof(struct ravb_ex_rx_desc),
+	.dbat_entry_num = 22,
 	.internal_delay = 1,
 	.tx_counters = 1,
 	.multi_irqs = 1,
@@ -2743,6 +2745,7 @@ static const struct ravb_hw_info ravb_gen4_hw_info = {
 	.rx_buffer_size = SZ_2K +
 			  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
 	.rx_desc_size = sizeof(struct ravb_ex_rx_desc),
+	.dbat_entry_num = 22,
 	.internal_delay = 1,
 	.tx_counters = 1,
 	.multi_irqs = 1,
@@ -2769,6 +2772,7 @@ static const struct ravb_hw_info ravb_rzv2m_hw_info = {
 	.rx_buffer_size = SZ_2K +
 			  SKB_DATA_ALIGN(sizeof(struct skb_shared_info)),
 	.rx_desc_size = sizeof(struct ravb_ex_rx_desc),
+	.dbat_entry_num = 22,
 	.multi_irqs = 1,
 	.err_mgmt_irqs = 1,
 	.gptp = 1,
@@ -2794,6 +2798,7 @@ static const struct ravb_hw_info gbeth_hw_info = {
 	.rx_max_frame_size = SZ_8K,
 	.rx_buffer_size = SZ_2K,
 	.rx_desc_size = sizeof(struct ravb_rx_desc),
+	.dbat_entry_num = 2,
 	.aligned_tx = 1,
 	.coalesce_irqs = 1,
 	.tx_counters = 1,
@@ -3025,7 +3030,7 @@ static int ravb_probe(struct platform_device *pdev)
 	ravb_parse_delay_mode(np, ndev);
 
 	/* Allocate descriptor base address table */
-	priv->desc_bat_size = sizeof(struct ravb_desc) * DBAT_ENTRY_NUM;
+	priv->desc_bat_size = sizeof(struct ravb_desc) * info->dbat_entry_num;
 	priv->desc_bat = dma_alloc_coherent(ndev->dev.parent, priv->desc_bat_size,
 					    &priv->desc_bat_dma, GFP_KERNEL);
 	if (!priv->desc_bat) {
@@ -3035,7 +3040,7 @@ static int ravb_probe(struct platform_device *pdev)
 		error = -ENOMEM;
 		goto out_rpm_put;
 	}
-	for (q = RAVB_BE; q < DBAT_ENTRY_NUM; q++)
+	for (q = RAVB_BE; q < info->dbat_entry_num; q++)
 		priv->desc_bat[q].die_dt = DT_EOS;
 
 	/* Initialise HW timestamp list */
-- 
2.43.0