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SubjectRe: [PATCH] net: phy: Fix c45 no phy detected logic
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Hi,

On 5/14/20 12:00 PM, Jeremy Linton wrote:
> The commit "disregard Clause 22 registers present bit..." clears
> the low bit of the devices_in_package data which is being used
> in get_phy_c45_ids() to determine if a phy/register is responding
> correctly. That check is against 0x1FFFFFFF, but since the low
> bit is always cleared, the check can never be true. This leads to
> detecting c45 phy devices where none exist.
>
> Lets fix this by also clearing the low bit in the mask to 0x1FFFFFFE.
> This allows us to continue to autoprobe standards compliant devices
> without also gaining a large number of bogus ones.

So, I've been reworking the c45 ID detection logic, with an aim to
hinting to the scanner that it should fallback to c22 for a given phy
address (as well as giving it some additional standardized areas to
probe for phy ids). It turns out that the c22 registers present bit is a
pretty useful signal that this needs to happen. So, I think this patch
really should move the BIT(0) sanitation after the MMD detection loop in
get_phy_c45_ids().

But having dug into this code for a while now, I'm hard pressed to
understand the case that the original 3b5e74e0afe3 commit fixed. The
only thing I can see is that the "bug" i'm fixing here was intentionally
creating bogus phy nodes when the MMDs weren't responding.


Thanks,

>
> Fixes: 3b5e74e0afe3 ("net: phy: disregard "Clause 22 registers present" bit in get_phy_c45_devs_in_pkg")
> Cc: Heiner Kallweit <hkallweit1@gmail.com>
> Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
> ---
> drivers/net/phy/phy_device.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index ac2784192472..b93d984d35cc 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -723,7 +723,7 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
> if (phy_reg < 0)
> return -EIO;
>
> - if ((*devs & 0x1fffffff) == 0x1fffffff) {
> + if ((*devs & 0x1ffffffe) == 0x1ffffffe) {
> /* If mostly Fs, there is no device there,
> * then let's continue to probe more, as some
> * 10G PHYs have zero Devices In package,
> @@ -733,7 +733,7 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
> if (phy_reg < 0)
> return -EIO;
> /* no device there, let's get out of here */
> - if ((*devs & 0x1fffffff) == 0x1fffffff) {
> + if ((*devs & 0x1ffffffe) == 0x1ffffffe) {
> *phy_id = 0xffffffff;
> return 0;
> } else {
>

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