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cxgb4vf: fix mailbox data/control coherency domain race

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For the VFs, the Mailbox Data "registers" are actually backed by
T4's "MA" interface rather than PL Registers (as is the case for
the PFs).  Because these are in different coherency domains, the
write to the VF's PL-register-backed Mailbox Control can race in
front of the writes to the MA-backed VF Mailbox Data "registers".
So we need to do a read-back on at least one byte of the VF Mailbox
Data registers before doing the write to the VF Mailbox Control
register.

Signed-off-by: Casey Leedom <leedom@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Casey Leedom 2011-01-10 13:53:43 -08:00 committed by David S. Miller
parent b11a25aaec
commit 80ce3f67e7
1 changed files with 11 additions and 0 deletions
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11
drivers/net/cxgb4vf/t4vf_hw.c
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@ -147,9 +147,20 @@ int t4vf_wr_mbox_core(struct adapter *adapter, const void *cmd, int size,
/*
* Write the command array into the Mailbox Data register array and
* transfer ownership of the mailbox to the firmware.
*
* For the VFs, the Mailbox Data "registers" are actually backed by
* T4's "MA" interface rather than PL Registers (as is the case for
* the PFs). Because these are in different coherency domains, the
* write to the VF's PL-register-backed Mailbox Control can race in
* front of the writes to the MA-backed VF Mailbox Data "registers".
* So we need to do a read-back on at least one byte of the VF Mailbox
* Data registers before doing the write to the VF Mailbox Control
* register.
*/
for (i = 0, p = cmd; i < size; i += 8)
t4_write_reg64(adapter, mbox_data + i, be64_to_cpu(*p++));
t4_read_reg(adapter, mbox_data); /* flush write */
t4_write_reg(adapter, mbox_ctl,
MBMSGVALID | MBOWNER(MBOX_OWNER_FW));
t4_read_reg(adapter, mbox_ctl); /* flush write */