qed: make 'ethtool -d' 10 times faster

As a side effect of commit 5401c3e ("qed: allow sleep in
qed_mcp_trace_dump()"), 'ethtool -d' became much slower.
Almost all the time is spent collecting the "mcp_trace".
It is caused by sleeping too long in _qed_mcp_cmd_and_union.
When called with sleeping not allowed, the function delays for 10 µs
between firmware polls. But if sleeping is allowed, it sleeps for 10 ms
instead.

The sleeps in _qed_mcp_cmd_and_union are unnecessarily long.
Replace msleep with usleep_range, which allows to achieve a similar
polling interval like in the no-sleeping mode (10 - 20 µs).

The only caller, qed_mcp_cmd_and_union, can stop doing the
multiplication/division of the usecs/max_retries. The polling interval
and the number of retries do not need to be parameters at all.

On my test system, 'ethtool -d' now takes 4 seconds instead of 44.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Link: https://patch.msgid.link/20240930201307.330692-2-mschmidt@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/qlogic/qed/qed_mcp.c

@@ -459,12 +459,11 @@ static void qed_mcp_print_cpu_info(struct qed_hwfn *p_hwfn,
 static int
 _qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 		       struct qed_ptt *p_ptt,
-		       struct qed_mcp_mb_params *p_mb_params,
-		       u32 max_retries, u32 usecs)
+		       struct qed_mcp_mb_params *p_mb_params)
 {
-	u32 cnt = 0, msecs = DIV_ROUND_UP(usecs, 1000);
 	struct qed_mcp_cmd_elem *p_cmd_elem;
 	u16 seq_num;
+	u32 cnt = 0;
 	int rc = 0;
 
 	/* Wait until the mailbox is non-occupied */
@@ -488,12 +487,13 @@ _qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 		spin_unlock_bh(&p_hwfn->mcp_info->cmd_lock);
 
 		if (QED_MB_FLAGS_IS_SET(p_mb_params, CAN_SLEEP))
-			msleep(msecs);
+			usleep_range(QED_MCP_RESP_ITER_US,
+				     QED_MCP_RESP_ITER_US * 2);
 		else
-			udelay(usecs);
-	} while (++cnt < max_retries);
+			udelay(QED_MCP_RESP_ITER_US);
+	} while (++cnt < QED_DRV_MB_MAX_RETRIES);
 
-	if (cnt >= max_retries) {
+	if (cnt >= QED_DRV_MB_MAX_RETRIES) {
 		DP_NOTICE(p_hwfn,
 			  "The MFW mailbox is occupied by an uncompleted command. Failed to send command 0x%08x [param 0x%08x].\n",
 			  p_mb_params->cmd, p_mb_params->param);
@@ -520,9 +520,10 @@ _qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 		 */
 
 		if (QED_MB_FLAGS_IS_SET(p_mb_params, CAN_SLEEP))
-			msleep(msecs);
+			usleep_range(QED_MCP_RESP_ITER_US,
+				     QED_MCP_RESP_ITER_US * 2);
 		else
-			udelay(usecs);
+			udelay(QED_MCP_RESP_ITER_US);
 
 		spin_lock_bh(&p_hwfn->mcp_info->cmd_lock);
 
@@ -536,9 +537,9 @@ _qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 			goto err;
 
 		spin_unlock_bh(&p_hwfn->mcp_info->cmd_lock);
-	} while (++cnt < max_retries);
+	} while (++cnt < QED_DRV_MB_MAX_RETRIES);
 
-	if (cnt >= max_retries) {
+	if (cnt >= QED_DRV_MB_MAX_RETRIES) {
 		DP_NOTICE(p_hwfn,
 			  "The MFW failed to respond to command 0x%08x [param 0x%08x].\n",
 			  p_mb_params->cmd, p_mb_params->param);
@@ -564,7 +565,8 @@ _qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 		   "MFW mailbox: response 0x%08x param 0x%08x [after %d.%03d ms]\n",
 		   p_mb_params->mcp_resp,
 		   p_mb_params->mcp_param,
-		   (cnt * usecs) / 1000, (cnt * usecs) % 1000);
+		   (cnt * QED_MCP_RESP_ITER_US) / 1000,
+		   (cnt * QED_MCP_RESP_ITER_US) % 1000);
 
 	/* Clear the sequence number from the MFW response */
 	p_mb_params->mcp_resp &= FW_MSG_CODE_MASK;
@@ -581,8 +583,6 @@ static int qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 				 struct qed_mcp_mb_params *p_mb_params)
 {
 	size_t union_data_size = sizeof(union drv_union_data);
-	u32 max_retries = QED_DRV_MB_MAX_RETRIES;
-	u32 usecs = QED_MCP_RESP_ITER_US;
 
 	/* MCP not initialized */
 	if (!qed_mcp_is_init(p_hwfn)) {
@@ -606,13 +606,7 @@ static int qed_mcp_cmd_and_union(struct qed_hwfn *p_hwfn,
 		return -EINVAL;
 	}
 
-	if (QED_MB_FLAGS_IS_SET(p_mb_params, CAN_SLEEP)) {
-		max_retries = DIV_ROUND_UP(max_retries, 1000);
-		usecs *= 1000;
-	}
-
-	return _qed_mcp_cmd_and_union(p_hwfn, p_ptt, p_mb_params, max_retries,
-				      usecs);
+	return _qed_mcp_cmd_and_union(p_hwfn, p_ptt, p_mb_params);
 }
 
 static int _qed_mcp_cmd(struct qed_hwfn *p_hwfn,