Messages in this thread | | | Date | Wed, 22 Nov 2023 17:24:33 +0000 | From | "Russell King (Oracle)" <> | Subject | Re: [net-next PATCH] net: phy: aquantia: drop wrong endianness conversion for addr and CRC |
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On Wed, Nov 22, 2023 at 06:08:13PM +0100, Christian Marangi wrote: > On further testing on BE target with kernel test robot, it was notice > that the endianness conversion for addr and CRC in fw_load_memory was > wrong and actually not needed. Values in define doesn't get converted > and are passed as is and hardcoded values are already in what the PHY > require, that is LE. > > Also drop the cpu_to_be32 for CRC calculation as it's wrong and use > _swab32 instead, the word is taked from firmware and is always LE, the
taken
> mailbox will emit a BE CRC hence the word needs to be always swapped and > the endianness of the host needs to be ignored.
I'm not convinced. If the firmware is a bytestream (as most "files" are) then for val = get_unaligned((u32 *)ptr), where ptr is an array of u8:
ptr[0] ptr[1] ptr[2] ptr[3] val on LE val on BE 0x01 0x02 0x03 0x04 0x04030201 0x01020304
So, endianness matters here, and I think as Jakub already suggested, you need to use get_unaligned_le32().
> diff --git a/drivers/net/phy/aquantia/aquantia_firmware.c b/drivers/net/phy/aquantia/aquantia_firmware.c > index c5f292b1c4c8..bd093633d0cf 100644 > --- a/drivers/net/phy/aquantia/aquantia_firmware.c > +++ b/drivers/net/phy/aquantia/aquantia_firmware.c > @@ -93,9 +93,9 @@ static int aqr_fw_load_memory(struct phy_device *phydev, u32 addr, > u16 crc = 0, up_crc; > size_t pos; > > - /* PHY expect addr in LE */ > - addr = (__force u32)cpu_to_le32(addr); > - > + /* PHY expect addr in LE. Hardcoded addr in defines are > + * already in this format. > + */ > phy_write_mmd(phydev, MDIO_MMD_VEND1, > VEND1_GLOBAL_MAILBOX_INTERFACE1, > VEND1_GLOBAL_MAILBOX_INTERFACE1_CRC_RESET); > @@ -128,7 +128,7 @@ static int aqr_fw_load_memory(struct phy_device *phydev, u32 addr, > * We convert word to big-endian as PHY is BE and mailbox will > * return a BE CRC. > */ > - word = (__force u32)cpu_to_be32(word); > + word = __swab32(word); > crc = crc_ccitt_false(crc, (u8 *)&word, sizeof(word));
Again, I think you need to be careful with the endianness here again. From what I understand here, it seems the CRC needs to be generated by looking at the byte at ptr[3] first, then ptr[2], ptr[1] and finally ptr[0] ?
If that is the case, the problem is using __swab32() on LE will do the job for you, but on BE machines, it will be wrong.
I would make this explicit:
u8 crc_data[4];
...
/* CRC is calculated using BE order */ crc_data[0] = word >> 24; crc_data[1] = word >> 16; crc_data[2] = word >> 8; crc_data[3] = word;
crc = crc_ccitt_false(crc, crc_data, sizeof(crc_data));
which will be (a) completely unambiguous, and (b) completely independent of the host endianness.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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