Patch "net: dsa: microchip: fix register write order in ksz8_ind_write8()" has been added to the 6.7-stable tree

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This is a note to let you know that I've just added the patch titled

    net: dsa: microchip: fix register write order in ksz8_ind_write8()

to the 6.7-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-dsa-microchip-fix-register-write-order-in-ksz8_i.patch
and it can be found in the queue-6.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit b3b8141c29989b67d3f87263614c32f40e0cbc5e
Author: Tobias Jakobi (Compleo) <tobias.jakobi.compleo@xxxxxxxxx>
Date:   Mon Mar 4 16:41:35 2024 +0100

    net: dsa: microchip: fix register write order in ksz8_ind_write8()
    
    [ Upstream commit b7fb7729c94fb2d23c79ff44f7a2da089c92d81c ]
    
    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@xxxxxxxxx>
    Reviewed-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
    Fixes: 7b6e6235b664 ("net: dsa: microchip: ksz8795: handle eee specif erratum")
    Link: https://lore.kernel.org/r/20240304154135.161332-1-tobias.jakobi.compleo@xxxxxxxxx
    Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/net/dsa/microchip/ksz8795.c b/drivers/net/dsa/microchip/ksz8795.c
index 4bf4d67557dcf..9048d1f196110 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);
 




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