From: Martin Blumenstingl martin.blumenstingl@googlemail.com
[ Upstream commit 433c6cab9d298687c097f6ee82e49157044dc7c6 ]
Meson8b only supports MPLL2 as clock input. The rate of the MPLL2 clock set by Odroid-C1's u-boot is close to (but not exactly) 500MHz. The exact rate is 500002394Hz, which is calculated in drivers/clk/meson/clk-mpll.c using the following formula: DIV_ROUND_UP_ULL((u64)parent_rate * SDM_DEN, (SDM_DEN * n2) + sdm) Odroid-C1's u-boot configures MPLL2 with the following values: - SDM_DEN = 16384 - SDM = 1638 - N2 = 5
The 250MHz clock (m250_div) inside dwmac-meson8b driver is derived from the MPLL2 clock. Due to MPLL2 running slightly faster than 500MHz the common clock framework chooses a divider which is too big to generate the 250MHz clock (a divider of 2 would be needed, but this is rounded up to a divider of 3). This breaks the RTL8211F RGMII PHY on Odroid-C1 because it requires a (close to) 125MHz RGMII TX clock (on Gbit speeds, the IP block internally divides that down to 25MHz on 100Mbit/s connections and 2.5MHz on 10Mbit/s connections - we don't need any special configuration for that).
Round the divider to the closest value to prevent this issue on Meson8b. This means we'll now end up with a clock rate for the RGMII TX clock of 125001197Hz (= 125MHz plus 1197Hz), which is close-enough to 125MHz. This has no effect on the Meson GX SoCs since there fclk_div2 is used as input clock, which has a rate of 1000MHz (and thus is divisible cleanly to 250MHz and 125MHz).
Fixes: 566e8251625304 ("net: stmmac: add a glue driver for the Amlogic Meson 8b / GXBB DWMAC") Reported-by: Emiliano Ingrassia ingrassia@epigenesys.com Signed-off-by: Martin Blumenstingl martin.blumenstingl@googlemail.com Reviewed-by: Jerome Brunet jbrunet@baylibre.com Tested-by: Jerome Brunet jbrunet@baylibre.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c index 4404650b32c5..157e12e15f28 100644 --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-meson8b.c @@ -144,7 +144,9 @@ static int meson8b_init_clk(struct meson8b_dwmac *dwmac) dwmac->m250_div.shift = PRG_ETH0_CLK_M250_DIV_SHIFT; dwmac->m250_div.width = PRG_ETH0_CLK_M250_DIV_WIDTH; dwmac->m250_div.hw.init = &init; - dwmac->m250_div.flags = CLK_DIVIDER_ONE_BASED | CLK_DIVIDER_ALLOW_ZERO; + dwmac->m250_div.flags = CLK_DIVIDER_ONE_BASED | + CLK_DIVIDER_ALLOW_ZERO | + CLK_DIVIDER_ROUND_CLOSEST;
dwmac->m250_div_clk = devm_clk_register(dev, &dwmac->m250_div.hw); if (WARN_ON(IS_ERR(dwmac->m250_div_clk)))