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.villem...@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.villem...@prevas.dk
www.prevas.dk
