Messages in this thread | | | Date | Tue, 17 Aug 2021 20:20:40 +0200 | From | Ben Hutchings <> | Subject | Re: [PATCH 5.10 51/96] net: dsa: microchip: Fix ksz_read64() |
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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
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