[PATCH RESEND net-next] net: stmmac: dwmac-rk: Provide FIFO sizes for DWMAC 1000

[Chen-Yu Tsai <wens@kernel.org>]

From: Chen-Yu Tsai <wens@csie.org>

The DWMAC 1000 DMA capabilities register does not provide actual
FIFO sizes, nor does the driver really care. If they are not
provided via some other means, the driver will work fine, only
disallowing changing the MTU setting.

The recent commit 8865d22656b4 ("net: stmmac: Specify hardware
capability value when FIFO size isn't specified") changed this by
requiring the FIFO sizes to be provided, breaking devices that were
working just fine.

Provide the FIFO sizes through the driver's platform data, to not
only fix the breakage, but also enable MTU changes. The FIFO sizes
are confirmed to be the same across RK3288, RK3328, RK3399 and PX30,
based on their respective manuals. It is likely that Rockchip
synthesized their DWMAC 1000 with the same parameters on all their
chips that have it.

Fixes: eaf4fac47807 ("net: stmmac: Do not accept invalid MTU values")
Fixes: 8865d22656b4 ("net: stmmac: Specify hardware capability value when FIFO size isn't specified")
Cc: <stable@vger.kernel.org>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
(Resending to net-next instead of netdev.)

The commit that broke things has already been reverted in netdev.

The reason for stable inclusion is not to fix the device breakage
(which only broke in v6.14-rc1), but to provide the values so that MTU
changes can work in older kernels.

 drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
index a4dc89e23a68..71a4c4967467 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-rk.c
@@ -1966,8 +1966,11 @@ static int rk_gmac_probe(struct platform_device *pdev)
 	/* If the stmmac is not already selected as gmac4,
 	 * then make sure we fallback to gmac.
 	 */
-	if (!plat_dat->has_gmac4)
+	if (!plat_dat->has_gmac4) {
 		plat_dat->has_gmac = true;
+		plat_dat->rx_fifo_size = 4096;
+		plat_dat->tx_fifo_size = 2048;
+	}
 	plat_dat->fix_mac_speed = rk_fix_speed;
 
 	plat_dat->bsp_priv = rk_gmac_setup(pdev, plat_dat, data);
-- 
2.39.5