On 6/19/24 15:14, Marek Vasut wrote:
On 6/19/24 9:41 AM, Christophe ROULLIER wrote:
Hi,
+static int stm32mp2_configure_syscfg(struct
plat_stmmacenet_data *plat_dat)
+{
+ struct stm32_dwmac *dwmac = plat_dat->bsp_priv;
+ u32 reg = dwmac->mode_reg;
+ int val = 0;
+
+ switch (plat_dat->mac_interface) {
+ case PHY_INTERFACE_MODE_MII:
+ break;
dwmac->enable_eth_ck does not apply to MII mode ? Why ?
It is like MP1 and MP13, nothing to set in syscfg register for
case MII mode wo crystal.
Have a look at STM32MP15xx RM0436 Figure 83. Peripheral clock
distribution for Ethernet.
If RCC (top-left corner of the figure) generates 25 MHz MII clock
(yellow line) on eth_clk_fb (top-right corner), can I set
ETH_REF_CLK_SEL to position '1' and ETH_SEL[2] to '0' and feed ETH
(right side) clk_rx_i input with 25 MHz clock that way ?
I seems like this should be possible, at least theoretically. Can
you check with the hardware/silicon people ?
No it is not possible (it will work if speed (and frequency) is
fixed 25Mhz=100Mbps, but for speed 10Mbps (2,5MHz) it will not work.
Could the pll4_p_ck or pll3_q_ck generate either 25 MHz or 2.5 MHz
as needed in that case ? Then it would work, right ?
Yes you can set frequency you want for pll4 or pll3, if you set 25MHz
and auto-negotiation of speed is 100Mbps it should work (pad ETH_CK
of 25MHz clock the PHY and eth_clk_fb set to 25MHz for clk_RX)
but if autoneg of speed is 10Mbps, then 2.5MHz is needed for clk_RX
(you will provide 25Mhz)
What if:
- Aneg is 10 Mbps
- PLL4_P_CK/PLL3_Q_CK = 2.5 MHz
- ETH_REF_CLK_SEL = 1
- ETH_SEL[2] = 0
?
Then, clk_rx_i is 2.5 MHz, right ?
Yes that right
Does this configuration work ?
For me no, because PHY Ethernet Oscillator/cristal need in PAD 25Mhz or
50Mhz, I think it is does not work if oscillator frequency provided is
2.5MHz (To my knowledge there is no Ethernet PHY which have oscillator
working to 2.5MHz)
. For RMII case, frequency from pll (eth_clk_fb) is automatically
adjust in function of speed value, thanks to diviser /2, /20 with
mac_speed_o.
