| Message ID | 20210816125436.659359567@linuxfoundation.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | None | expand |
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; > }
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
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; }