RE: [EXT] Re: [PATCH v3 net 2/2] net: stmmac: dwmac-imx: pause the TXC clock in fixed-link

[Shenwei Wang]

> -----Original Message-----
> From: Russell King <linux@xxxxxxxxxxxxxxx>
> Sent: Tuesday, August 1, 2023 7:57 AM
> To: Johannes Zink <j.zink@xxxxxxxxxxxxxx>
> Cc: Shenwei Wang <shenwei.wang@xxxxxxx>; David S. Miller
> <davem@xxxxxxxxxxxxx>; Eric Dumazet <edumazet@xxxxxxxxxx>; Jakub
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> Subject: [EXT] Re: [PATCH v3 net 2/2] net: stmmac: dwmac-imx: pause the TXC
> clock in fixed-link
>
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> On Tue, Aug 01, 2023 at 02:47:46PM +0200, Johannes Zink wrote:
> > Hi Shenwei,
> >
> > thanks for your patch.
> >
> > On 7/31/23 18:19, Shenwei Wang wrote:
> > > When using a fixed-link setup, certain devices like the SJA1105
> > > require a small pause in the TXC clock line to enable their internal
> > > tunable delay line (TDL).
> >
> > If this is only required for some devices, is it safe to enforce this
> > behaviour unconditionally for any kind of fixed link devices connected
> > to the MX93 EQOS or could this possibly break for other devices?
>
> This same point has been raised by Andrew Halaney in message-id
> <4govb566nypifbtqp5lcbsjhvoyble5luww3onaa2liinboguf@4kgihys6vhrg>
> and Fabio Estevam in message-id
>
> <CAOMZO5ANQmVbk_jy7qdVtzs3716FisT2c72W+3WZyu7FoAochw@mail.gmail.
> com>
> but we don't seem to have any answer for it.
>
Hi Russell,

I hope you have thoroughly read all of my earlier responses, as I believe I already addressed this question.
I'm happy to clarify further, but kindly avoid unsubstantiated comments.

https://lore.kernel.org/imx/20230727152503.2199550-1-shenwei.wang@xxxxxxx/T/#m08da3797a056d4d8ea4c1d8956b445ae967e7cfa
" Yes, that's the purpose because it won't hurt even the other side is not SJA1105."

> Also, the patch still uses wmb() between the write and the delay, and as Will
> Deacon pointed out in his message, message-id
> <20230728153611.GH21718@willie-the-truck>
> this is not safe, yet still a new version was sent.
>

Can we conclude that even without the wmb() here, the desired delay time between
operations can still be ensured?

Thanks,
Shenwei

> It seems the author of these patches is pretty resistant to comments, and has
> shown that when I was requesting changes - it was an awful struggle to get
> changes made. I'm now of the opinion that I really can't be bothered to review
> these patches, precisely because feedback is clearly not welcome or if welcome,
> apparently acted upon.
>
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