linux-kernel - Re: [PATCH] net: phy: Fix c45 no phy detected logic

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Date:   Thu, 14 May 2020 15:49:18 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Heiner Kallweit <hkallweit1@...il.com>, netdev@...r.kernel.org
Cc:     andrew@...n.ch, f.fainelli@...il.com, linux@...linux.org.uk,
        davem@...emloft.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: Fix c45 no phy detected logic

Hi,

On 5/14/20 2:59 PM, Heiner Kallweit wrote:
> On 14.05.2020 19:00, 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.
>>
>> Fixes: 3b5e74e0afe3 ("net: phy: disregard "Clause 22 registers present" bit in get_phy_c45_devs_in_pkg")
>> Cc: Heiner Kallweit <hkallweit1@...il.com>
>> Signed-off-by: Jeremy Linton <jeremy.linton@....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,
> 
> Looks good to me, it would just be good to extend the comment and explain
> why we exclude bit 0 here.

Sure, sounds good.

> 
> 
>>   			 *  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 {
>>
>