From: Ben Hutchings <[email protected]>
[ Upstream commit c34f674c8875235725c3ef86147a627f165d23b4 ]
ksz_read64() currently does some dubious byte-swapping on the two
halves of a 64-bit register, and then only returns the high bits.
Replace this with a straightforward expression.
Fixes: e66f840c08a2 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
Signed-off-by: Ben Hutchings <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
---
drivers/net/dsa/microchip/ksz_common.h | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index cf866e48ff66..a51c716ec920 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -210,12 +210,8 @@ static inline int ksz_read64(struct ksz_device *dev, u32 reg, u64 *val)
int ret;
ret = regmap_bulk_read(dev->regmap[2], reg, value, 2);
- if (!ret) {
- /* Ick! ToDo: Add 64bit R/W to regmap on 32bit systems */
- value[0] = swab32(value[0]);
- value[1] = swab32(value[1]);
- *val = swab64((u64)*value);
- }
+ if (!ret)
+ *val = (u64)value[0] << 32 | value[1];
return ret;
}
--
2.30.2
Hi!
> [ Upstream commit c34f674c8875235725c3ef86147a627f165d23b4 ]
>
> ksz_read64() currently does some dubious byte-swapping on the two
> halves of a 64-bit register, and then only returns the high bits.
> Replace this with a straightforward expression.
The code indeed is very strange, but there are just 2 users, and they
will now receive byteswapped values, right? If it worked before, it
will be broken.
Did this get enough testing for -stable?
Is hw little endian or high endian or...? Note that ksz_write64()
still contains the strange code, at least in 5.10.
Best regards,
Pavel
> +++ b/drivers/net/dsa/microchip/ksz_common.h
> @@ -210,12 +210,8 @@ static inline int ksz_read64(struct ksz_device *dev, u32 reg, u64 *val)
> int ret;
>
> ret = regmap_bulk_read(dev->regmap[2], reg, value, 2);
> - if (!ret) {
> - /* Ick! ToDo: Add 64bit R/W to regmap on 32bit systems */
> - value[0] = swab32(value[0]);
> - value[1] = swab32(value[1]);
> - *val = swab64((u64)*value);
> - }
> + if (!ret)
> + *val = (u64)value[0] << 32 | value[1];
>
> return ret;
> }
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
On Tue, Aug 17, 2021 at 07:56:30PM +0200, Pavel Machek wrote:
> Hi!
>
> > [ Upstream commit c34f674c8875235725c3ef86147a627f165d23b4 ]
> >
> > ksz_read64() currently does some dubious byte-swapping on the two
> > halves of a 64-bit register, and then only returns the high bits.
> > Replace this with a straightforward expression.
>
> The code indeed is very strange, but there are just 2 users, and they
> will now receive byteswapped values, right? If it worked before, it
> will be broken.
The old code swaps the bytes within each 32-bit word, attempts to
concatenate them into a 64-bit word, then swaps the bytes within the
64-bit word. There is no need for byte-swapping, only (on little-
endian platforms) a word-swap, which is what the new code does.
> Did this get enough testing for -stable?
Yes, I actually developed and tested all the ksz8795 changes in 5.10
before forward-porting to mainline.
> Is hw little endian or high endian or...?
The hardware is big-endian and regmap handles any necessary
byte-swapping for values up to 32 bits.
> Note that ksz_write64() still contains the strange code, at least in
> 5.10.
It's unnecessarily complex, but it does work.
Ben.
>
> Best regards,
> Pavel
>
> > +++ b/drivers/net/dsa/microchip/ksz_common.h
> > @@ -210,12 +210,8 @@ static inline int ksz_read64(struct ksz_device *dev, u32 reg, u64 *val)
> > int ret;
> >
> > ret = regmap_bulk_read(dev->regmap[2], reg, value, 2);
> > - if (!ret) {
> > - /* Ick! ToDo: Add 64bit R/W to regmap on 32bit systems */
> > - value[0] = swab32(value[0]);
> > - value[1] = swab32(value[1]);
> > - *val = swab64((u64)*value);
> > - }
> > + if (!ret)
> > + *val = (u64)value[0] << 32 | value[1];
> >
> > return ret;
> > }
>
> --
> DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
--
Ben Hutchings ? Senior Embedded Software Engineer, Essensium-Mind ? mind.be
Hi!
> > > [ Upstream commit c34f674c8875235725c3ef86147a627f165d23b4 ]
> > >
> > > ksz_read64() currently does some dubious byte-swapping on the two
> > > halves of a 64-bit register, and then only returns the high bits.
> > > Replace this with a straightforward expression.
> >
> > The code indeed is very strange, but there are just 2 users, and they
> > will now receive byteswapped values, right? If it worked before, it
> > will be broken.
>
> The old code swaps the bytes within each 32-bit word, attempts to
> concatenate them into a 64-bit word, then swaps the bytes within the
> 64-bit word. There is no need for byte-swapping, only (on little-
> endian platforms) a word-swap, which is what the new code does.
>
> > Did this get enough testing for -stable?
>
> Yes, I actually developed and tested all the ksz8795 changes in 5.10
> before forward-porting to mainline.
>
> > Is hw little endian or high endian or...?
>
> The hardware is big-endian and regmap handles any necessary
> byte-swapping for values up to 32 bits.
>
> > Note that ksz_write64() still contains the strange code, at least in
> > 5.10.
>
> It's unnecessarily complex, but it does work.
Thanks for the explanations and sorry for the noise. Indeed
ksz_write64() is quite obfuscated, but I can't see a problem.
Best regards,
Pavel
--
DENX Software Engineering GmbH, Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany