From: <shh....@gmail.com>
Date: Thu, 29 Oct 2015 17:09:37 +0800
> From: Shaohui Xie <shaohui....@freescale.com>
>
> When probing devices-in-package for a c45 phy, device zero is the last
> device to probe, in a rare situation which driver can read a '0' from
> the device zero, thus c45_ids->devices_in_package is set to '0', so the
> loop condition of probing is matched, see codes below:
>
> for (i = 1;i < num_ids && c45_ids->devices_in_package == 0;i++)
>
> driver will run in a dead loop.
>
> So after probing the device zero, driver should stop the probing loop.
>
> Signed-off-by: Shaohui Xie <shaohui....@freescale.com>
This bug only exists because the loop is extremely confusing.
Please fix this by restructuring the loop:
1) Break out this code:
reg_addr = MII_ADDR_C45 | i << 16 | MDIO_DEVS2;
phy_reg = mdiobus_read(bus, addr, reg_addr);
if (phy_reg < 0)
return -EIO;
c45_ids->devices_in_package = (phy_reg & 0xffff) << 16;
reg_addr = MII_ADDR_C45 | i << 16 | MDIO_DEVS1;
phy_reg = mdiobus_read(bus, addr, reg_addr);
if (phy_reg < 0)
return -EIO;
c45_ids->devices_in_package |= (phy_reg & 0xffff);
into a helper function that takes "c45_ids, bus, addr, i" as arguments
and returns an error, either 0 or -EIO. Call it "phy_check_devs_in_pkg"
or similar.
2) Rewrite the loop as:
for (i = 1;
i < num_ids && c45_ids->devices_in_package == 0;
i++) {
err = phy_check_devs_in_pkg(c45_ids, bus, addr, i);
if (err < 0)
return err;
if ((c45_ids->devices_in_package & 0x1fffffff) == 0x1fffffff) {
if (i) {
/* If mostly Fs, there is no device there,
* then let's continue to probe more, as some
* 10G PHYs have zero Devices In package,
* e.g. Cortina CS4315/CS4340 PHY.
*/
err = phy_check_devs_in_pkg(c45_ids, bus, addr,
0);
if (err)
return err;
break;
}
} else {
/* no device there, let's get out of here */
*phy_id = 0xffffffff;
return 0;
}
}
}
Thanks.
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