net: stmmac: dwmac-meson8b: fix setting the RGMII TX clock on Meson8b
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: 566e8251 ("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>
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