netdev - Re: [PATCH v2 1/2] stmmac: Expose module parameters

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Date:   Thu, 18 Aug 2022 14:15:39 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Feiyang Chen <chris.chenfeiyang@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, peppe.cavallaro@...com,
        alexandre.torgue@...s.st.com, joabreu@...opsys.com,
        Feiyang Chen <chenfeiyang@...ngson.cn>, zhangqing@...ngson.cn,
        Huacai Chen <chenhuacai@...ngson.cn>, netdev@...r.kernel.org,
        loongarch@...ts.linux.dev
Subject: Re: [PATCH v2 1/2] stmmac: Expose module parameters

On Thu, Aug 18, 2022 at 02:41:11PM +0800, Feiyang Chen wrote:
> On Thu, 18 Aug 2022 at 11:05, Jakub Kicinski <kuba@...nel.org> wrote:
> >
> > On Wed, 17 Aug 2022 15:29:18 +0800 chris.chenfeiyang@...il.com wrote:
> > > Expose module parameters so that we can use them in specific device
> > > configurations. Add the 'stmmac_' prefix for them to avoid conflicts.
> > >
> > > Meanwhile, there was a 'buf_sz' local variable in stmmac_rx() with the
> > > same name as the global variable, and now we can distinguish them.
> >
> > Can you provide more information on the 'why'?
> 
> Hi, Jakub,
> 
> We would like to be able to change these properties when configuring
> the device data. For example, Loongson GMAC does not support Flow
> Control feature, and exposing these parameters allows us to ensure
> that flow control is off in the Loongson GMAC device.

Two comments:

One patch should do one thing, with a commit message which explains why.

The MAC needs to tell phylib about what it can do in terms of
pause. The MAC would normally call phy_set_sym_pause(phydev, False, False) and then
the PHY will not auto-get any pause, and as a result, the MAC will never to asked
to enable any sort of flow control.

   Andrew