From: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Vivien Didelot <vivien.didelot@gmail.com>,
Florian Fainelli <f.fainelli@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Rasmus Villemoes <Rasmus.Villemoes@prevas.se>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] net: dsa: mv88e6xxx: fix handling of upper half of STATS_TYPE_PORT
Date: Wed, 29 May 2019 06:42:53 +0000 [thread overview]
Message-ID: <dc84827e-6bac-7a01-f998-609cfe9a33ec@prevas.dk> (raw)
In-Reply-To: <20190528134458.GE18059@lunn.ch>
On 28/05/2019 15.44, Andrew Lunn wrote:
> On Tue, May 28, 2019 at 01:17:10PM +0000, Rasmus Villemoes wrote:
>> Currently, the upper half of a 4-byte STATS_TYPE_PORT statistic ends
>> up in bits 47:32 of the return value, instead of bits 31:16 as they
>> should.
>>
>> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
>
> Hi Rasmus
>
> Please include a Fixes tag, to indicate where the problem was
> introduced. In this case, i think it was:
>
> Fixes: 6e46e2d821bb ("net: dsa: mv88e6xxx: Fix u64 statistics")
>
> And set the Subject to [PATCH net] to indicate this should be applied
> to the net tree.
Will do.
>> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
>> index 370434bdbdab..317553d2cb21 100644
>> --- a/drivers/net/dsa/mv88e6xxx/chip.c
>> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
>> @@ -785,7 +785,7 @@ static uint64_t _mv88e6xxx_get_ethtool_stat(struct mv88e6xxx_chip *chip,
>> err = mv88e6xxx_port_read(chip, port, s->reg + 1, ®);
>> if (err)
>> return U64_MAX;
>> - high = reg;
>> + low |= ((u32)reg) << 16;
>> }
>> break;
>> case STATS_TYPE_BANK1:
>
> What i don't like about this is how the function finishes:
>
> }
> value = (((u64)high) << 32) | low;
> return value;
> }
>
> A better fix might be
>
> - break
> + value = (((u64)high) << 16 | low;
> + return value;
Why? It's odd to have the u32 "high" sometimes represent the high 32
bits, sometimes the third 16 bits. It would make it harder to support an
8-byte STATS_TYPE_PORT statistic. I think the code is much cleaner if
each case is just responsible for providing the upper/lower 32 bits,
then have the common case combine them; . It's just that in the
STATS_TYPE_BANK cases, the 32 bits are assembled from two 16 bit values
by a helper (mv88e6xxx_g1_stats_read), while it is "open-coded" in the
first case.
I'll resend my patch with the fixes tag (thanks for finding that; I had
already dug way too deep past that one) and fixed subject.
Rasmus
> Andrew
>
--
Rasmus Villemoes
Software Developer
Prevas A/S
Hedeager 3
DK-8200 Aarhus N
+45 51210274
rasmus.villemoes@prevas.dk
www.prevas.dk
next prev parent reply other threads:[~2019-05-29 6:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-28 13:17 [PATCH] net: dsa: mv88e6xxx: fix handling of upper half of STATS_TYPE_PORT Rasmus Villemoes
2019-05-28 13:44 ` Andrew Lunn
2019-05-29 6:42 ` Rasmus Villemoes [this message]
2019-05-29 17:10 ` Vivien Didelot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=dc84827e-6bac-7a01-f998-609cfe9a33ec@prevas.dk \
--to=rasmus.villemoes@prevas.dk \
--cc=Rasmus.Villemoes@prevas.se \
--cc=andrew@lunn.ch \
--cc=davem@davemloft.net \
--cc=f.fainelli@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=vivien.didelot@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).