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 <[email protected]>
---
I also noticed that it's a bit inconsistent that we return U64_MAX if
there's a read error in STATS_TYPE_PORT, while
mv88e6xxx_g1_stats_read() returns 0 in case of a read error. In
practice, register reads probably never fail so it doesn't matter.
drivers/net/dsa/mv88e6xxx/chip.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
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:
--
2.20.1
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 <[email protected]>
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.
> ---
> I also noticed that it's a bit inconsistent that we return U64_MAX if
> there's a read error in STATS_TYPE_PORT, while
> mv88e6xxx_g1_stats_read() returns 0 in case of a read error. In
> practice, register reads probably never fail so it doesn't matter.
>
> drivers/net/dsa/mv88e6xxx/chip.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> 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;
Andrew
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 <[email protected]>
>
> 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
[email protected]
http://www.prevas.dk
Hi Rasmus, Andrew,
On Wed, 29 May 2019 06:42:53 +0000, Rasmus Villemoes <[email protected]> wrote:
> 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 <[email protected]>
> >
> > 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.
Here "low" and "high" are u32 and refer to the upper and lower halves
of the u64 returned value. For a 4-byte STATS_TYPE_PORT value, the
second read refers to the bits 31:16, thus belongs to (the upper half
of) the lower half of the 64-bit returned value, i.e. "low".
The current return value is correct, as well as your patch.
Thanks,
Vivien