linux-kernel - [PATCH AUTOSEL 6.14 456/642] net: stmmac: dwmac-loongson: Set correct {tx,rx}_fifo

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Message-Id: <20250505221419.2672473-456-sashal@kernel.org>
Date: Mon,  5 May 2025 18:11:12 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Huacai Chen <chenhuacai@...ngson.cn>,
	Yanteng Si <si.yanteng@...ux.dev>,
	Simon Horman <horms@...nel.org>,
	Chong Qiao <qiaochong@...ngson.cn>,
	Jakub Kicinski <kuba@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	pabeni@...hat.com,
	mcoquelin.stm32@...il.com,
	alexandre.torgue@...s.st.com,
	chenhuacai@...nel.org,
	chenfeiyang@...ngson.cn,
	fancer.lancer@...il.com,
	phasta@...nel.org,
	zhaoqunqin@...ngson.cn,
	rmk+kernel@...linux.org.uk,
	netdev@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 6.14 456/642] net: stmmac: dwmac-loongson: Set correct {tx,rx}_fifo_size

From: Huacai Chen <chenhuacai@...ngson.cn>

[ Upstream commit 8dbf0c7556454b52af91bae305ca71500c31495c ]

Now for dwmac-loongson {tx,rx}_fifo_size are uninitialised, which means
zero. This means dwmac-loongson doesn't support changing MTU because in
stmmac_change_mtu() it requires the fifo size be no less than MTU. Thus,
set the correct tx_fifo_size and rx_fifo_size for it (16KB multiplied by
queue counts).

Here {tx,rx}_fifo_size is initialised with the initial value (also the
maximum value) of {tx,rx}_queues_to_use. So it will keep as 16KB if we
don't change the queue count, and will be larger than 16KB if we change
(decrease) the queue count. However stmmac_change_mtu() still work well
with current logic (MTU cannot be larger than 16KB for stmmac).

Note: the Fixes tag picked here is the oldest commit and key commit of
the dwmac-loongson series "stmmac: Add Loongson platform support".

Acked-by: Yanteng Si <si.yanteng@...ux.dev>
Reviewed-by: Simon Horman <horms@...nel.org>
Signed-off-by: Chong Qiao <qiaochong@...ngson.cn>
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
Link: https://patch.msgid.link/20250210134328.2755328-1-chenhuacai@loongson.cn
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
index ab7c2750c1042..702ea5a00b56d 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c
@@ -590,6 +590,9 @@ static int loongson_dwmac_probe(struct pci_dev *pdev, const struct pci_device_id
 	if (ret)
 		goto err_disable_device;
 
+	plat->tx_fifo_size = SZ_16K * plat->tx_queues_to_use;
+	plat->rx_fifo_size = SZ_16K * plat->rx_queues_to_use;
+
 	if (dev_of_node(&pdev->dev))
 		ret = loongson_dwmac_dt_config(pdev, plat, &res);
 	else
-- 
2.39.5