linux-kernel - Re: [PATCH net-next v4 02/15] net: dsa: vsc73xx: convert to PHYLINK

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Date: Wed, 14 Feb 2024 13:56:10 +0100
From: Paweł Dembicki <paweldembicki@...il.com>
To: Florian Fainelli <f.fainelli@...il.com>
Cc: netdev@...r.kernel.org, linus.walleij@...aro.org, 
	Andrew Lunn <andrew@...n.ch>, Vladimir Oltean <olteanv@...il.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Claudiu Manoil <claudiu.manoil@....com>, Alexandre Belloni <alexandre.belloni@...tlin.com>, 
	UNGLinuxDriver@...rochip.com, Russell King <linux@...linux.org.uk>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v4 02/15] net: dsa: vsc73xx: convert to PHYLINK

śr., 14 lut 2024 o 00:19 Florian Fainelli <f.fainelli@...il.com> napisał(a):
>
> On 2/13/24 14:03, Pawel Dembicki wrote:
> > This patch replaces the adjust_link api with the phylink apis that provide
> > equivalent functionality.
> >
> > The remaining functionality from the adjust_link is now covered in the
> > phylink_mac_link_* and phylink_mac_config.
> >
> > Removes:
> > .adjust_link
> > Adds:
> > .phylink_mac_config
> > .phylink_mac_link_up
> > .phylink_mac_link_down
>
> The implementation of phylink_mac_link_down() strictly mimics what had
> been done by adjust_link() in the phydev->link == 0 case, but it really
> makes me wonder whether some bits do not logically belong to
> phylink_mac_link_up(), like "Accept packets again" for instance.
>
> Are we certain there was not an assumption before that we would get
> adjust_link() called first with phydev->link = 0, and then phydev->link
> =1 and that this specific sequence would program things just the way we
> want?

Yes, it was the simplest conversion possible, without any improvements.

Some part is implementation of datasheet (description of ARBEMPTY register):

        /* Discard packets */
        vsc73xx_update_bits(vsc, VSC73XX_BLOCK_ARBITER, 0,
                            VSC73XX_ARBDISC, BIT(port), BIT(port));

        /* Wait until queue is empty */
        ret = read_poll_timeout(vsc73xx_read, err, err < 0 || (val & BIT(port)),
                                1000, 10000, false, vsc, VSC73XX_BLOCK_ARBITER,
                                0, VSC73XX_ARBEMPTY, &val);
        if (ret)
                dev_err(vsc->dev,
                        "timeout waiting for block arbiter\n");
        else if (err < 0)
                dev_err(vsc->dev, "error reading arbiter\n");

        /* Put this port into reset */
        vsc73xx_write(vsc, VSC73XX_BLOCK_MAC, port, VSC73XX_MAC_CFG,
                      VSC73XX_MAC_CFG_RESET);


I agree that VSC73XX_ARBDISC should be moved to phylink_mac_link_up.
Other things could be optimised and it needs more care. (eg. This
implementation doesn't disable phy when the interface goes down.) I
plan to tweak it after the driver becomes usable. Please let me know
if it should be fixed in this patch.

-- 
Best Regards,
Pawel Dembicki