From mboxrd@z Thu Jan 1 00:00:00 1970 From: Casey Leedom Subject: [PATCH net-26] cxgb4vf: fix mailbox data/control coherency domain race Date: Mon, 10 Jan 2011 13:51:01 -0800 Message-ID: <1294696261-21209-1-git-send-email-leedom@chelsio.com> Cc: davem@davemloft.net, Casey Leedom To: netdev@vger.kernel.org Return-path: Received: from stargate.chelsio.com ([67.207.112.58]:2252 "EHLO stargate.chelsio.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752874Ab1AJVvH (ORCPT ); Mon, 10 Jan 2011 16:51:07 -0500 Sender: netdev-owner@vger.kernel.org List-ID: 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 --- drivers/net/cxgb4vf/t4vf_hw.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) diff --git a/drivers/net/cxgb4vf/t4vf_hw.c b/drivers/net/cxgb4vf/t4vf_hw.c index e4bec78..0f51c80 100644 --- a/drivers/net/cxgb4vf/t4vf_hw.c +++ b/drivers/net/cxgb4vf/t4vf_hw.c @@ -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 */ -- 1.7.0.4