Re: [PATCH 5.10 51/96] net: dsa: microchip: Fix ksz_read64()

Pavel Machek
2021-08-17T17:56:40Z

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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;
> }

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