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SubjectRe: [RFC 03/11] net: phy: refactor c45 phy identification sequence
On Fri, May 22, 2020 at 04:30:51PM -0500, Jeremy Linton wrote:
> Lets factor out the phy id logic, and make it generic
> so that it can be used for c22 and c45.
>
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
> drivers/net/phy/phy_device.c | 65 +++++++++++++++++++-----------------
> 1 file changed, 35 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 7746c07b97fe..f0761fa5e40b 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -695,6 +695,29 @@ static int get_phy_c45_devs_in_pkg(struct mii_bus *bus, int addr, int dev_addr,
> return 0;
> }
>
> +static int _get_phy_id(struct mii_bus *bus, int addr, int dev_addr,
> + u32 *phy_id, bool c45)
> +{
> + int phy_reg, reg_addr;
> +
> + int reg_base = c45 ? (MII_ADDR_C45 | dev_addr << 16) : 0;

int phy_reg, reg_addr, reg_base;

reg_base = c45 ? (MII_ADDR_C45 | dev_addr << 16) : 0;

I think would be preferable.

> +
> + reg_addr = reg_base | MII_PHYSID1;
> + phy_reg = mdiobus_read(bus, addr, reg_addr);
> + if (phy_reg < 0)
> + return -EIO;
> +
> + *phy_id = phy_reg << 16;
> +
> + reg_addr = reg_base | MII_PHYSID2;
> + phy_reg = mdiobus_read(bus, addr, reg_addr);
> + if (phy_reg < 0)
> + return -EIO;
> + *phy_id |= phy_reg;

The line spacing seems to be a little inconsistent between the above two
register reads.

> +
> + return 0;
> +}

So, _get_phy_id() returns either zero or -EIO.

> +
> static bool valid_phy_id(int val)
> {
> return (val > 0 && ((val & 0x1fffffff) != 0x1fffffff));
> @@ -715,17 +738,17 @@ static bool valid_phy_id(int val)
> */
> static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
> struct phy_c45_device_ids *c45_ids) {
> - int phy_reg;
> - int i, reg_addr;
> + int ret;
> + int i;
> const int num_ids = ARRAY_SIZE(c45_ids->device_ids);
> u32 *devs = &c45_ids->devices_in_package;

I feel a "reverse christmas tree" complaint brewing... yes, the original
code didn't follow it. Maybe a tidy up while touching this code?

>
> /* Find first non-zero Devices In package. Device zero is reserved
> * for 802.3 c45 complied PHYs, so don't probe it at first.
> */
> - for (i = 1; i < num_ids && *devs == 0; i++) {
> - phy_reg = get_phy_c45_devs_in_pkg(bus, addr, i, devs);
> - if (phy_reg < 0)
> + for (i = 0; i < num_ids && *devs == 0; i++) {
> + ret = get_phy_c45_devs_in_pkg(bus, addr, i, devs);
> + if (ret < 0)
> return -EIO;
>
> if ((*devs & 0x1fffffff) == 0x1fffffff) {
> @@ -752,17 +775,9 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
> if (!(c45_ids->devices_in_package & (1 << i)))
> continue;
>
> - reg_addr = MII_ADDR_C45 | i << 16 | MII_PHYSID1;
> - phy_reg = mdiobus_read(bus, addr, reg_addr);
> - if (phy_reg < 0)
> - return -EIO;
> - c45_ids->device_ids[i] = phy_reg << 16;
> -
> - reg_addr = MII_ADDR_C45 | i << 16 | MII_PHYSID2;
> - phy_reg = mdiobus_read(bus, addr, reg_addr);
> - if (phy_reg < 0)
> - return -EIO;
> - c45_ids->device_ids[i] |= phy_reg;
> + ret = _get_phy_id(bus, addr, i, &c45_ids->device_ids[i], true);
> + if (ret < 0)
> + return ret;

So here we can only propagate the -EIO, so this keeps the semantics.

> }
> *phy_id = 0;
> return 0;
> @@ -787,27 +802,17 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
> static int get_phy_id(struct mii_bus *bus, int addr, u32 *phy_id,
> bool is_c45, struct phy_c45_device_ids *c45_ids)
> {
> - int phy_reg;
> + int ret;
>
> if (is_c45)
> return get_phy_c45_ids(bus, addr, phy_id, c45_ids);
>
> - /* Grab the bits from PHYIR1, and put them in the upper half */
> - phy_reg = mdiobus_read(bus, addr, MII_PHYSID1);
> - if (phy_reg < 0) {
> + ret = _get_phy_id(bus, addr, 0, phy_id, false);
> + if (ret < 0) {
> /* returning -ENODEV doesn't stop bus scanning */
> - return (phy_reg == -EIO || phy_reg == -ENODEV) ? -ENODEV : -EIO;
> + return (ret == -EIO || ret == -ENODEV) ? -ENODEV : -EIO;

Since ret will only ever be -EIO here, this can only ever return
-ENODEV, which is a functional change in the code (probably unintended.)
Nevertheless, it's likely introducing a bug if the intention is for
some other return from mdiobus_read() to be handled differently.

> }
>
> - *phy_id = phy_reg << 16;
> -
> - /* Grab the bits from PHYIR2, and put them in the lower half */
> - phy_reg = mdiobus_read(bus, addr, MII_PHYSID2);
> - if (phy_reg < 0)
> - return -EIO;

... whereas this one always returns -EIO on any error.

So, I think you have the potential in this patch to introduce a subtle
change of behaviour, which may lead to problems - have you closely
analysed why the code was the way it was, and whether your change of
behaviour is actually valid?

> -
> - *phy_id |= phy_reg;
> -
> return 0;
> }
>
> --
> 2.26.2
>
>

--
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