Re: [PATCH] net: macb: ignore tx_clk if MII is used

Michael Walle
2021-01-21T09:43:51Z

Hi Claudiu,

Am 2021-01-21 10:19, schrieb Claudiu.Beznea@microchip.com:
> On 20.01.2021 21:43, Michael Walle wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
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>>
>> If the MII interface is used, the PHY is the clock master, thus don't
>> set the clock rate. On Zynq-7000, this will prevent the following
>> warning:
>> macb e000b000.ethernet eth0: unable to generate target frequency:
>> 25000000 Hz
>>
>
> Since in this case the PHY provides the TX clock and it provides the
> proper
> rate based on link speed, the MACB driver should not handle the
> bp->tx_clk
> at all (MACB driver uses this clock only for setting the proper rate on
> it
> based on link speed). So, I believe the proper fix would be to not pass
> the
> tx_clk at all in device tree. This clock is optional for MACB driver.

Thanks for looking into this.

I had the same thought. But shouldn't the driver handle this case
gracefully?
I mean it does know that the clock isn't needed at all. Ususually that
clock
is defined in a device tree include. So you'd have to redefine that node
in
an actual board file which means duplicating the other clocks.

-michael