[PATCH 1/2] net: fec_mxc: Fix clk_ref rate on iMX93

[Ye Li]

Hi Fabio, Primoz, Peng,


On 9/24/2024 10:56 AM, Peng Fan wrote:
>> Subject: Re: [PATCH 1/2] net: fec_mxc: Fix clk_ref rate on iMX93
>>
>> Hi,
>>
>> On 23. 09. 24 15:14, Peng Fan (OSS) wrote:
>>> From: Ye Li <ye.li at nxp.com>
>>>
>>> Because iMX93 has a internal 1/2 divider before clock input to
>> network
>>> controller, so have to set twice frequency rate
>>>
>>> Fixes: 09de565f76b ("net: fec_mxc: support i.MX93")
>>> Signed-off-by: Ye Li <ye.li at nxp.com>
>>> Signed-off-by: Peng Fan <peng.fan at nxp.com>
>>> ---
>>>   drivers/net/fec_mxc.c | 3 +++
>>>   1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/net/fec_mxc.c b/drivers/net/fec_mxc.c index
>>> 0a0d92bc2cd..e5d7f0f3e1e 100644
>>> --- a/drivers/net/fec_mxc.c
>>> +++ b/drivers/net/fec_mxc.c
>>> @@ -1215,6 +1215,9 @@ static int fecmxc_set_ref_clk(struct clk
>> *clk_ref, phy_interface_t interface)
>>>   	else
>>>   		return -EINVAL;
>>>
>>> +	if (is_imx93())
>>> +		freq = freq << 1;
>> Humm, but how did it work so far?
>>
>> On phyboard-segin-imx93, this change breaks fec ethernet.
>>
>> I had to revert this already in NXP downstream u-boot.
> Ah. If you set enet_ref_clk to 250M, then you no need
> this change. Otherwise you need this change.
>
> Regards,
> Peng.

Just check phyboard-segin-imx93, this board uses RMII not RGMII. It 
outputs CCM clk_enet_ref on pin ENET1_TX_CLK to external phy for 
reference clock and loop back it on pad to FEC as RMII clock. So this 
usage has bypassed the 1/2 divider since the 1/2 divider is inside 
wakeupmix not on path CCM clk_enet_ref to pad.  We need to change the 
patch to limit the 1/2 divider only for RGMII on iMX93.

In kernel, clk_enet_ref is assigned by dts, I don't see its rate changed 
by driver like u-boot.


Best regards,

Ye Li

>> BR,
>> Primoz
>>
>>
>>> +
>>>   	ret = clk_set_rate(clk_ref, freq);
>>>   	if (ret < 0)
>>>   		return ret;
>> --
>> Primoz Fiser                    | phone: +386-41-390-545
>> <tel:+386-41-390-545> |
>> ---------------------------------------------------------|
>> Norik systems d.o.o.            |
>> https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2F
>> www.norik.com%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C482
>> 464a6990d46e9668808dcdbd135d9%7C686ea1d3bc2b4c6fa92cd99c
>> 5c301635%7C0%7C0%7C638626938825379940%7CUnknown%7CTW
>> FpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haW
>> wiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=kkO%2FnCs8%2FjpZ4ez
>> JYDHo5T57jmUVPdp%2Fs34CnpwrsGM%3D&reserved=0
>> <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2
>> Fwww.norik.com%2F&data=05%7C02%7Cpeng.fan%40nxp.com%7C48
>> 2464a6990d46e9668808dcdbd135d9%7C686ea1d3bc2b4c6fa92cd99
>> c5c301635%7C0%7C0%7C638626938825421127%7CUnknown%7CT
>> WFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
>> WwiLCJXVCI6Mn0%3D%7C0%7C%7C%7C&sdata=0YIItswvK9V9zEcn83I
>> h0IRjyzNGvqkM7vq4bXnajRI%3D&reserved=0>  | Your embedded
>> software partner  | email: info at norik.com <mailto:info at norik.com> |
>> Slovenia, EU                    | phone: +386-41-540-545
>> <tel:+386-41-540-545> |