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".

Cc: stable@vger.kernel.org Fixes: ad72f783de06 ("net: stmmac: Add multi-channel support") Acked-by: Yanteng Si si.yanteng@linux.dev Reviewed-by: Simon Horman horms@kernel.org Signed-off-by: Chong Qiao qiaochong@loongson.cn Signed-off-by: Huacai Chen chenhuacai@loongson.cn --- V2: Update commit message and CC list.

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 bfe6e2d631bd..79acdf38c525 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson.c @@ -574,6 +574,9 @@ 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