On Fri, May 14, 2021 at 9:09 AM Russell King (Oracle)
[off-list ref] wrote:

Hi!

On Fri, May 14, 2021 at 07:58:26AM -0400, Peter Geis wrote:

quoted

+     /* set rgmii delay mode */
+     val = __phy_read(phydev, YT8511_PAGE);
+
+     switch (phydev->interface) {
+     case PHY_INTERFACE_MODE_RGMII:
+             val &= ~(YT8511_DELAY_RX | YT8511_DELAY_TX);
+             break;
+     case PHY_INTERFACE_MODE_RGMII_ID:
+             val |= YT8511_DELAY_RX | YT8511_DELAY_TX;
+             break;
+     case PHY_INTERFACE_MODE_RGMII_RXID:
+             val &= ~(YT8511_DELAY_TX);
+             val |= YT8511_DELAY_RX;
+             break;
+     case PHY_INTERFACE_MODE_RGMII_TXID:
+             val &= ~(YT8511_DELAY_RX);
+             val |= YT8511_DELAY_TX;
+             break;
+     default: /* leave everything alone in other modes */
+             break;
+     }
+
+     ret = __phy_write(phydev, YT8511_PAGE, val);
+     if (ret < 0)
+             goto err_restore_page;

Another way of writing the above is to set "val" to be the value of the
YT8511_DELAY_RX and YT8511_DELAY_TX bits, and then do:

        ret = __phy_modify(phydev, YT8511_PAGE,
                           (YT8511_DELAY_RX | YT8511_DELAY_TX), val);
        if (ret < 0)
                goto err_restore_page;

which moves the read-modify-write out of the driver into core code and
makes the driver code smaller. It also handles your missing error check
on __phy_read() above - would you want the above code to attempt to
write a -ve error number back to this register? I suspect not!

That makes sense, thanks!
I was thinking about how to use __phy_modify with a functional mask,
but it didn't click until I had already sent it in.
Also thanks for catching handling that ret on the read!

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