Re: [PATCH net-next 1/6] net: dsa: vsc73xx: convert to PHYLINK

Paweł Dembicki
2023-06-24T04:02:46Z

czw., 22 cze 2023 o 13:55 Russell King (Oracle)
<linux@armlinux.org.uk> napisał(a):
>
> On Wed, Jun 21, 2023 at 09:12:56PM +0200, Pawel Dembicki wrote:
> > + /* This driver does not make use of the speed, duplex, pause or the
> > + * advertisement in its mac_config, so it is safe to mark this driver
> > + * as non-legacy.
> > + */
> > + config->legacy_pre_march2020 = false;
>
> Great stuff, thanks!
>
> > +static void vsc73xx_phylink_mac_config(struct dsa_switch *ds, int port,
> > + unsigned int mode,
> > + const struct phylink_link_state *state)
> > +{
> > + struct vsc73xx *vsc = ds->priv;
>
> Nit: normally have a blank line between function variable declarations
> and the rest of the function body.
>
> > /* Special handling of the CPU-facing port */
> > if (port == CPU_PORT) {
> > /* Other ports are already initialized but not this one */
> > @@ -775,104 +803,92 @@ static void vsc73xx_adjust_link(struct dsa_switch *ds, int port,
> > VSC73XX_ADVPORTM_ENA_GTX |
> > VSC73XX_ADVPORTM_DDR_MODE);
> > }
> > +}
> >
> > - /* This is the MAC confiuration that always need to happen
> > - * after a PHY or the CPU port comes up or down.
> > - */
> > - if (!phydev->link) {
> > - int maxloop = 10;
> > +static void vsc73xx_phylink_mac_link_down(struct dsa_switch *ds, int port,
> > + unsigned int mode,
> > + phy_interface_t interface)
> > +{
> > + struct vsc73xx *vsc = ds->priv;
> > + u32 val;
> >
> > - dev_dbg(vsc->dev, "port %d: went down\n",
> > - port);
> > + int maxloop = VSC73XX_TABLE_ATTEMPTS;
>
> Reverse christmas-tree for variable declarations, and there shouldn't
> be a blank line between them. In any case, I don't think you need
> "maxloop" if you adopt my suggestion below.
>
> >
> > - /* Disable RX on this port */
> > - vsc73xx_update_bits(vsc, VSC73XX_BLOCK_MAC, port,
> > - VSC73XX_MAC_CFG,
> > - VSC73XX_MAC_CFG_RX_EN, 0);
> > + dev_dbg(vsc->dev, "port %d: went down\n",
> > + port);
> >
> > - /* Discard packets */
> > - vsc73xx_update_bits(vsc, VSC73XX_BLOCK_ARBITER, 0,
> > - VSC73XX_ARBDISC, BIT(port), BIT(port));
> > + /* Disable RX on this port */
> > + vsc73xx_update_bits(vsc, VSC73XX_BLOCK_MAC, port,
> > + VSC73XX_MAC_CFG,
> > + VSC73XX_MAC_CFG_RX_EN, 0);
> > +
> > + /* Discard packets */
> > + vsc73xx_update_bits(vsc, VSC73XX_BLOCK_ARBITER, 0,
> > + VSC73XX_ARBDISC, BIT(port), BIT(port));
> >
> > - /* Wait until queue is empty */
> > + /* Wait until queue is empty */
> > + vsc73xx_read(vsc, VSC73XX_BLOCK_ARBITER, 0,
> > + VSC73XX_ARBEMPTY, &val);
> > + while (!(val & BIT(port))) {
> > + msleep(1);
> > vsc73xx_read(vsc, VSC73XX_BLOCK_ARBITER, 0,
> > VSC73XX_ARBEMPTY, &val);
> > - while (!(val & BIT(port))) {
> > - msleep(1);
> > - vsc73xx_read(vsc, VSC73XX_BLOCK_ARBITER, 0,
> > - VSC73XX_ARBEMPTY, &val);
> > - if (--maxloop == 0) {
> > - dev_err(vsc->dev,
> > - "timeout waiting for block arbiter\n");
> > - /* Continue anyway */
> > - break;
> > - }
> > + if (--maxloop == 0) {
> > + dev_err(vsc->dev,
> > + "timeout waiting for block arbiter\n");
> > + /* Continue anyway */
> > + break;
> > }
> > + }
>
> I know you're only moving this code, but I think it would be good to
> _first_ have a patch that fixes this polling function:
>
> int ret, err;
> ...
> 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 != 0)
> dev_err(vsc->dev,
> "timeout waiting for block arbiter\n");
> else if (err < 0)
> dev_err(vsc->dev,
> "error reading arbiter\n");
>
> This avoids the issue that on the last iteration, the code reads the
> register, test it, find the condition that's being waiting for is
> false, _then_ waits and end up printing the error message - that last
> wait is rather useless, and as the arbiter state isn't checked after
> waiting, it could be that we had success during the last wait.
>

Thank you for the tips. I will prepare additional commit in v2 series.

> > +static void vsc73xx_phylink_mac_link_up(struct dsa_switch *ds, int port,
> > + unsigned int mode,
> > + phy_interface_t interface,
> > + struct phy_device *phydev,
> > + int speed, int duplex,
> > + bool tx_pause, bool rx_pause)
> > +{
> > + struct vsc73xx *vsc = ds->priv;
> > + u32 val;
> >
> > + switch (speed) {
> > + case SPEED_1000:
> > /* Set up default for internal port or external RGMII */
> > - if (phydev->interface == PHY_INTERFACE_MODE_RGMII)
> > + if (interface == PHY_INTERFACE_MODE_RGMII)
> > val = VSC73XX_MAC_CFG_1000M_F_RGMII;
> > else
> > val = VSC73XX_MAC_CFG_1000M_F_PHY;
> > - vsc73xx_adjust_enable_port(vsc, port, phydev, val);
> > - } else if (phydev->speed == SPEED_100) {
> > - if (phydev->duplex == DUPLEX_FULL) {
> > - val = VSC73XX_MAC_CFG_100_10M_F_PHY;
> > - dev_dbg(vsc->dev,
> > - "port %d: 100 Mbit full duplex mode\n",
> > - port);
> > - } else {
> > - val = VSC73XX_MAC_CFG_100_10M_H_PHY;
> > - dev_dbg(vsc->dev,
> > - "port %d: 100 Mbit half duplex mode\n",
> > - port);
> > - }
> > - vsc73xx_adjust_enable_port(vsc, port, phydev, val);
> > - } else if (phydev->speed == SPEED_10) {
> > - if (phydev->duplex == DUPLEX_FULL) {
> > + break;
> > + case SPEED_100:
> > + case SPEED_10:
> > + if (duplex == DUPLEX_FULL)
> > val = VSC73XX_MAC_CFG_100_10M_F_PHY;
> > - dev_dbg(vsc->dev,
> > - "port %d: 10 Mbit full duplex mode\n",
> > - port);
> > - } else {
> > + else
> > val = VSC73XX_MAC_CFG_100_10M_H_PHY;
> > - dev_dbg(vsc->dev,
> > - "port %d: 10 Mbit half duplex mode\n",
> > - port);
> > - }
> > - vsc73xx_adjust_enable_port(vsc, port, phydev, val);
> > - } else {
> > - dev_err(vsc->dev,
> > - "could not adjust link: unknown speed\n");
> > + break;
> > }
>
> Do the dev_dbg() add anything useful over what phylink prints when the
> link comes up?
>
> I don't think moving to a switch() statement for this is a good idea.
> Given that "val" may be uninitialised, I suspect the following may be
> a better solution:
>
> if (speed == SPEED_1000 || speed == SPEED_100 || speed == SPEED_10) {
> if (speed == SPEED_1000) {
> ...
> } else {
> ...
> }
>
> ... set VSC73XX_BLOCK_ANALYZER and call
> vsc73xx_adjust_enable_port ...
> }
>
> However, looking at the definitions of the various macros, it seems we
> can do a little better by not using the VSC73XX_MAC_CFG_*M_[FH]_*
> definitions:
>
> if (speed == SPEED_1000) {
> val = VSC73XX_MAC_CFG_GIGA_MODE |
> VSC73XX_MAC_CFG_TX_IPG_1000M;
>
> if (interface == PHY_INTERFACE_MODE_RGMII)
> val |= VSC73XX_MAC_CFG_CLK_SEL_1000M;
> else
> val |= VSC73XX_MAC_CFG_CLK_SEL_EXT;
> } else {
> val = VSC73XX_MAC_CFG_TX_IPG_100_10M |
> VSC73XX_MAC_CFG_CLK_SEL_EXT;
> }
>
> if (duplex == DUPLEX_FULL)
> val |= VSC73XX_MAC_CFG_FDX;
>
> Now, this reveals a question: when operating in RGMII mode, why do we
> need VSC73XX_MAC_CFG_CLK_SEL_1000M for 1G, and
> VSC73XX_MAC_CFG_CLK_SEL_EXT for 10M and 100M, whereas "PHY" mode always
> uses CLK_SEL_EXT ?
>

VSC73XX_MAC_CFG_CLK_SEL_EXT should be used always when phy is used, no
matter what speed is. VSC73XX_MAC_CFG_CLK_SEL_1000M in RGMII mode. It
can be even more simplified:

if (speed == SPEED_1000)
val = VSC73XX_MAC_CFG_GIGA_MODE | VSC73XX_MAC_CFG_TX_IPG_1000M;
else
val = VSC73XX_MAC_CFG_TX_IPG_100_10M;

if (interface == PHY_INTERFACE_MODE_RGMII)
val |= VSC73XX_MAC_CFG_CLK_SEL_1000M;
else
val |= VSC73XX_MAC_CFG_CLK_SEL_EXT;

if (duplex == DUPLEX_FULL)
val |= VSC73XX_MAC_CFG_FDX;

--
Pawel Dembicki