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

[Shenwei Wang]

> -----Original Message-----
> From: Russell King <linux at armlinux.org.uk>
> Sent: Wednesday, July 26, 2023 10:09 AM
> To: Shenwei Wang <shenwei.wang at nxp.com>
> Cc: David S. Miller <davem at davemloft.net>; Eric Dumazet
> <edumazet at google.com>; Jakub Kicinski <kuba at kernel.org>; Paolo Abeni
> <pabeni at redhat.com>; Maxime Coquelin <mcoquelin.stm32 at gmail.com>;
> Shawn Guo <shawnguo at kernel.org>; dl-linux-imx <linux-imx at nxp.com>;
> Giuseppe Cavallaro <peppe.cavallaro at st.com>; Alexandre Torgue
> <alexandre.torgue at foss.st.com>; Jose Abreu <joabreu at synopsys.com>; Sascha
> Hauer <s.hauer at pengutronix.de>; Pengutronix Kernel Team
> <kernel at pengutronix.de>; Fabio Estevam <festevam at gmail.com>;
> netdev at vger.kernel.org; linux-stm32 at st-md-mailman.stormreply.com; linux-
> arm-kernel at lists.infradead.org; imx at lists.linux.dev; Frank Li <frank.li at nxp.com>
> Subject: Re: [EXT] Re: [PATCH] net: stmmac: dwmac-imx: pause the TXC clock in
> fixed-link
>
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>
> On Wed, Jul 26, 2023 at 03:00:49PM +0000, Shenwei Wang wrote:
> >
> >
> > > -----Original Message-----
> > > From: Russell King <linux at armlinux.org.uk>
> > > Sent: Tuesday, July 25, 2023 4:05 PM
> > > To: Shenwei Wang <shenwei.wang at nxp.com>
> > > Cc: David S. Miller <davem at davemloft.net>; Eric Dumazet
> > > <edumazet at google.com>; Jakub Kicinski <kuba at kernel.org>; Paolo Abeni
> > > <pabeni at redhat.com>; Maxime Coquelin <mcoquelin.stm32 at gmail.com>;
> > > Shawn Guo <shawnguo at kernel.org>; dl-linux-imx <linux-imx at nxp.com>;
> > > Giuseppe Cavallaro <peppe.cavallaro at st.com>; Alexandre Torgue
> > > <alexandre.torgue at foss.st.com>; Jose Abreu <joabreu at synopsys.com>;
> > > Sascha Hauer <s.hauer at pengutronix.de>; Pengutronix Kernel Team
> > > <kernel at pengutronix.de>; Fabio Estevam <festevam at gmail.com>;
> > > netdev at vger.kernel.org; linux-stm32 at st-md-mailman.stormreply.com;
> > > linux- arm-kernel at lists.infradead.org; imx at lists.linux.dev; Frank Li
> > > <frank.li at nxp.com>
> > > Subject: [EXT] Re: [PATCH] net: stmmac: dwmac-imx: pause the TXC
> > > clock in fixed-link
> > >
> > > Caution: This is an external email. Please take care when clicking
> > > links or opening attachments. When in doubt, report the message
> > > using the 'Report this email' button
> > >
> > >
> > > On Tue, Jul 25, 2023 at 02:49:31PM -0500, Shenwei Wang wrote:
> > > > +static bool imx_dwmac_is_fixed_link(struct imx_priv_data *dwmac) {
> > > > +     struct plat_stmmacenet_data *plat_dat;
> > > > +     struct device_node *dn;
> > > > +
> > > > +     if (!dwmac || !dwmac->plat_dat)
> > > > +             return false;
> > > > +
> > > > +     plat_dat = dwmac->plat_dat;
> > > > +     dn = of_get_child_by_name(dwmac->dev->of_node, "fixed-link");
> > > > +     if (!dn)
> > > > +             return false;
> > > > +
> > > > +     if (plat_dat->phy_node == dn || plat_dat->phylink_node == dn)
> > > > +             return true;
> > >
> > > Why would the phy_node or the phylink_node ever be pointing at the
> > > fixed-link node?
> > >
> >
> > The logic was learned from the function of stmmac_probe_config_dt, and
> > it normally save the phy handle to those two members: phy_node and
> > phylink_node. But seems checking phy_node is enough here, right?
> >
> >         plat->phy_node = of_parse_phandle(np, "phy-handle", 0);
> >
> >         /* PHYLINK automatically parses the phy-handle property */
> >         plat->phylink_node = np;
>
> So, plat->phy_node will never ever be equal to your "dn" above.
> plat->phylink_node is the same as dwmac->dev->of_node above, and
> so plat->phylink_node will never be your "dn" above either.
>
> Those two together means that imx_dwmac_is_fixed_link() will _always_ return
> false, and thus most of the code you're adding is rather useless.
>
> It also means the code you're submitting probably hasn't been properly tested.
>
> Have you confirmed that imx_dwmac_is_fixed_link() will actually return true in
> your testing? Under what conditions did your testing reveal a true return value
> from this function?
>

We can't make that assumption. In my testing code, I had trace statements in that
section to indicate the code was actually executed. You may get some clues from the following DTS:

+&eqos {
+       pinctrl-names = "default";
+       pinctrl-0 = <&pinctrl_eqos_rgmii>;
+       phy-mode = "rgmii-rxid";
+       phy-handle = <&fixed0>;
+       status = "okay";
+
+       fixed0: fixed-link {
+               speed = <1000>;
+               full-duplex;
+       };
+
+       mdio {
+               compatible = "snps,dwmac-mdio";
+               #address-cells = <1>;
+               #size-cells = <0>;
+               clock-frequency = <2500000>;
+
+               phy0: ethernet-phy at 8 {
+                       reg = <0x8>;
+                       max-speed = <100>;
+                       #address-cells = <1>;
+                       #size-cells = <0>;
+
+                       phy1: ethernet-phy at 9 {
+                               reg = <0x9>;
+                               max-speed = <100>;
+                       };
+               };
...


Thanks,
Shenwei



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