qed*: Fix link indication race

Driver changes the link properties via communication with
the management firmware, and re-reads the resulting link status
when it receives an indication that the link has changed.
However, there are certain scenarios where such indications
might be missing, and so driver also re-reads the current link
results without attention in several places. Specifically, it
does so during load and when resetting the link.

This creates a race where driver might reflect incorrect
link status - e.g., when explicit reading of the link status is
switched by attention with the changed configuration.

Correct this flow by a lock syncronizing the handling of the
link indications [both explicit requests and attention].

Signed-off-by: Yuval Mintz <Yuval.Mintz@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 4 deletions

diff --git a/drivers/net/ethernet/qlogic/qed/qed_mcp.c b/drivers/net/ethernet/qlogic/qed/qed_mcp.c
index 7624a38cbd39..314022df3469 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_mcp.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_mcp.c
@@ -192,6 +192,7 @@ int qed_mcp_cmd_init(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt)
 
 	/* Initialize the MFW spinlock */
 	spin_lock_init(&p_info->lock);
+	spin_lock_init(&p_info->link_lock);
 
 	return 0;
 
@@ -610,6 +611,9 @@ static void qed_mcp_handle_link_change(struct qed_hwfn *p_hwfn,
 	u8 max_bw, min_bw;
 	u32 status = 0;
 
+	/* Prevent SW/attentions from doing this at the same time */
+	spin_lock_bh(&p_hwfn->mcp_info->link_lock);
+
 	p_link = &p_hwfn->mcp_info->link_output;
 	memset(p_link, 0, sizeof(*p_link));
 	if (!b_reset) {
@@ -624,7 +628,7 @@ static void qed_mcp_handle_link_change(struct qed_hwfn *p_hwfn,
 	} else {
 		DP_VERBOSE(p_hwfn, NETIF_MSG_LINK,
 			   "Resetting link indications\n");
-		return;
+		goto out;
 	}
 
 	if (p_hwfn->b_drv_link_init)
@@ -731,6 +735,8 @@ static void qed_mcp_handle_link_change(struct qed_hwfn *p_hwfn,
 	p_link->sfp_tx_fault = !!(status & LINK_STATUS_SFP_TX_FAULT);
 
 	qed_link_update(p_hwfn);
+out:
+	spin_unlock_bh(&p_hwfn->mcp_info->link_lock);
 }
 
 int qed_mcp_set_link(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt, bool b_up)
@@ -780,9 +786,13 @@ int qed_mcp_set_link(struct qed_hwfn *p_hwfn, struct qed_ptt *p_ptt, bool b_up)
 		return rc;
 	}
 
-	/* Reset the link status if needed */
-	if (!b_up)
-		qed_mcp_handle_link_change(p_hwfn, p_ptt, true);
+	/* Mimic link-change attention, done for several reasons:
+	 *  - On reset, there's no guarantee MFW would trigger
+	 *    an attention.
+	 *  - On initialization, older MFWs might not indicate link change
+	 *    during LFA, so we'll never get an UP indication.
+	 */
+	qed_mcp_handle_link_change(p_hwfn, p_ptt, !b_up);
 
 	return 0;
 }