diff options
| author | Tobias Jakobi (Compleo) | 2024-03-04 16:41:35 +0100 |
|---|---|---|
| committer | Jakub Kicinski | 2024-03-05 19:10:49 -0800 |
| commit | b7fb7729c94fb2d23c79ff44f7a2da089c92d81c (patch) | |
| tree | 77f42c9cc7474f53aa29d656b178b3f032669b30 /drivers | |
| parent | 289e922582af5b4721ba02e86bde4d9ba918158a (diff) | |
net: dsa: microchip: fix register write order in ksz8_ind_write8()
This bug was noticed while re-implementing parts of the kernel
driver in userspace using spidev. The goal was to enable some
of the errata workarounds that Microchip describes in their
errata sheet [1].
Both the errata sheet and the regular datasheet of e.g. the KSZ8795
imply that you need to do this for indirect register accesses:
- write a 16-bit value to a control register pair (this value
consists of the indirect register table, and the offset inside
the table)
- either read or write an 8-bit value from the data storage
register (indicated by REG_IND_BYTE in the kernel)
The current implementation has the order swapped. It can be
proven, by reading back some indirect register with known content
(the EEE register modified in ksz8_handle_global_errata() is one of
these), that this implementation does not work.
Private discussion with Oleksij Rempel of Pengutronix has revealed
that the workaround was apparantly never tested on actual hardware.
[1] https://ww1.microchip.com/downloads/aemDocuments/documents/OTH/ProductDocuments/Errata/KSZ87xx-Errata-DS80000687C.pdf
Signed-off-by: Tobias Jakobi (Compleo) <tobias.jakobi.compleo@gmail.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
Fixes: 7b6e6235b664 ("net: dsa: microchip: ksz8795: handle eee specif erratum")
Link: https://lore.kernel.org/r/20240304154135.161332-1-tobias.jakobi.compleo@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/net/dsa/microchip/ksz8795.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c index 61b71bcfe396..c3da97abce20 100644 --- a/drivers/net/dsa/microchip/ksz8795.c +++ b/drivers/net/dsa/microchip/ksz8795.c @@ -49,9 +49,9 @@ static int ksz8_ind_write8(struct ksz_device *dev, u8 table, u16 addr, u8 data) mutex_lock(&dev->alu_mutex); ctrl_addr = IND_ACC_TABLE(table) | addr; - ret = ksz_write8(dev, regs[REG_IND_BYTE], data); + ret = ksz_write16(dev, regs[REG_IND_CTRL_0], ctrl_addr); if (!ret) - ret = ksz_write16(dev, regs[REG_IND_CTRL_0], ctrl_addr); + ret = ksz_write8(dev, regs[REG_IND_BYTE], data); mutex_unlock(&dev->alu_mutex); |