netdev - Re: [PATCH v8 net-next 11/11] net: ethernet: ti: am65-cpsw: Fix get_eth_mac

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Date: Fri, 15 Dec 2023 13:31:17 +0200
From: Roger Quadros <rogerq@...nel.org>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, shuah@...nel.org, s-vadapalli@...com,
 r-gunasekaran@...com, vigneshr@...com, srk@...com, horms@...nel.org,
 p-varis@...com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 net-next 11/11] net: ethernet: ti: am65-cpsw: Fix
 get_eth_mac_stats



On 14/12/2023 12:04, Roger Quadros wrote:
> 
> 
> On 13/12/2023 15:54, Vladimir Oltean wrote:
>> On Wed, Dec 13, 2023 at 01:07:21PM +0200, Roger Quadros wrote:
>>> We do not support individual stats for PMAC and EMAC so
>>> report only aggregate stats.
>>>
>>> Fixes: 67372d7a85fc ("net: ethernet: am65-cpsw: Add standard Ethernet MAC stats to ethtool")
>>> Signed-off-by: Roger Quadros <rogerq@...nel.org>
>>> ---
>>>  drivers/net/ethernet/ti/am65-cpsw-ethtool.c | 3 +++
>>>  1 file changed, 3 insertions(+)
>>>
>>> Changelog:
>>>
>>> v8: initial commit
>>>
>>> diff --git a/drivers/net/ethernet/ti/am65-cpsw-ethtool.c b/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
>>> index d2baffb05d55..35e318458b0c 100644
>>> --- a/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
>>> +++ b/drivers/net/ethernet/ti/am65-cpsw-ethtool.c
>>> @@ -671,6 +671,9 @@ static void am65_cpsw_get_eth_mac_stats(struct net_device *ndev,
>>>  
>>>  	stats = port->stat_base;
>>>  
>>> +	if (s->src != ETHTOOL_MAC_STATS_SRC_AGGREGATE)
>>> +		return;
>>> +
>>>  	s->FramesTransmittedOK = readl_relaxed(&stats->tx_good_frames);
>>>  	s->SingleCollisionFrames = readl_relaxed(&stats->tx_single_coll_frames);
>>>  	s->MultipleCollisionFrames = readl_relaxed(&stats->tx_mult_coll_frames);
>>> -- 
>>> 2.34.1
>>>
>>
>> Fixes are only fixes if they address a visible issue. And the blamed
>> commit is the one that made the issue visible - the same one that
>> "git bisect" would lead to - not necessarily the commit that introduced
>> the code being changed.
>>
>> If you look at net/ethtool/stats.c, it will only accept ETHTOOL_MAC_STATS_SRC_AGGREGATE
>> for drivers that don't support the MAC Merge layer.
>>
>> 	if ((src == ETHTOOL_MAC_STATS_SRC_EMAC ||
>> 	     src == ETHTOOL_MAC_STATS_SRC_PMAC) &&
>> 	    !__ethtool_dev_mm_supported(dev)) {
>> 		NL_SET_ERR_MSG_MOD(info->extack,
>> 				   "Device does not support MAC merge layer");
>> 		ethnl_ops_complete(dev);
>> 		return -EOPNOTSUPP;
>> 	}
> 
> Got it.
> 
>>
>> So, there was nothing broken in commit 67372d7a85fc ("net: ethernet:
>> am65-cpsw: Add standard Ethernet MAC stats to ethtool").
>>
>> The first broken commit is when you add support for get_mm(), such that
>> __ethtool_dev_mm_supported() returns true.
>>
>> And because you don't add bugs in the code just to fix them later in the
>> series, you need to order the patches such that all the dependencies for
>> get_mm() are in place before the get_mm() support is added.
>>
>> Translated to your case, this patch must not be 11/11, and it must have
>> the Fixes: tag dropped, and it must explain in the commit message that
>> it is preparatory work.
> 
> OK. I take care of this in next spin. Thanks.

Just a heads up. I have decided to merge this patch with mac-merge patch.
One less patch to deal with ;).

-- 
cheers,
-roger