i40e: reduce stack usage in i40e_set_fc

The functions i40e_aq_get_phy_abilities_resp() and i40e_set_fc() both
have giant structure on the stack, which makes each one use stack frames
larger than 500 bytes.

As clang decides one function into the other, we get a warning for
exceeding the frame size limit on 32-bit architectures:

drivers/net/ethernet/intel/i40e/i40e_common.c:1654:23: error: stack frame size of 1116 bytes in function 'i40e_set_fc' [-Werror,-Wframe-larger-than=]

When building with gcc, the inlining does not happen, but i40e_set_fc()
calls i40e_aq_get_phy_abilities_resp() anyway, so they add up on the
kernel stack just as much.

The parts that actually use large stacks don't overlap, so make sure
each one is a separate function, and mark them as noinline_for_stack to
prevent the compilers from combining them again.

Fixes: 0a862b43 ("i40e/i40evf: Add module_types and update_link_info")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e_common.c

@@ -1643,25 +1643,15 @@ enum i40e_status_code i40e_aq_set_phy_config(struct i40e_hw *hw,
 	return status;
 }
 
-/**
- * i40e_set_fc
- * @hw: pointer to the hw struct
- * @aq_failures: buffer to return AdminQ failure information
- * @atomic_restart: whether to enable atomic link restart
- *
- * Set the requested flow control mode using set_phy_config.
- **/
-enum i40e_status_code i40e_set_fc(struct i40e_hw *hw, u8 *aq_failures,
+static noinline_for_stack enum i40e_status_code
+i40e_set_fc_status(struct i40e_hw *hw,
+		   struct i40e_aq_get_phy_abilities_resp *abilities,
 		   bool atomic_restart)
 {
-	enum i40e_fc_mode fc_mode = hw->fc.requested_mode;
-	struct i40e_aq_get_phy_abilities_resp abilities;
 	struct i40e_aq_set_phy_config config;
-	enum i40e_status_code status;
+	enum i40e_fc_mode fc_mode = hw->fc.requested_mode;
 	u8 pause_mask = 0x0;
 
-	*aq_failures = 0x0;
-
 	switch (fc_mode) {
 	case I40E_FC_FULL:
 		pause_mask |= I40E_AQ_PHY_FLAG_PAUSE_TX;
@@ -1677,39 +1667,60 @@ enum i40e_status_code i40e_set_fc(struct i40e_hw *hw, u8 *aq_failures,
 		break;
 	}
 
-	/* Get the current phy config */
-	status = i40e_aq_get_phy_capabilities(hw, false, false, &abilities,
-					      NULL);
-	if (status) {
-		*aq_failures |= I40E_SET_FC_AQ_FAIL_GET;
-		return status;
-	}
-
 	memset(&config, 0, sizeof(struct i40e_aq_set_phy_config));
 	/* clear the old pause settings */
-	config.abilities = abilities.abilities & ~(I40E_AQ_PHY_FLAG_PAUSE_TX) &
+	config.abilities = abilities->abilities & ~(I40E_AQ_PHY_FLAG_PAUSE_TX) &
 			   ~(I40E_AQ_PHY_FLAG_PAUSE_RX);
 	/* set the new abilities */
 	config.abilities |= pause_mask;
 	/* If the abilities have changed, then set the new config */
-	if (config.abilities != abilities.abilities) {
+	if (config.abilities == abilities->abilities)
+		return 0;
+
 	/* Auto restart link so settings take effect */
 	if (atomic_restart)
 		config.abilities |= I40E_AQ_PHY_ENABLE_ATOMIC_LINK;
 	/* Copy over all the old settings */
-		config.phy_type = abilities.phy_type;
-		config.phy_type_ext = abilities.phy_type_ext;
-		config.link_speed = abilities.link_speed;
-		config.eee_capability = abilities.eee_capability;
-		config.eeer = abilities.eeer_val;
-		config.low_power_ctrl = abilities.d3_lpan;
-		config.fec_config = abilities.fec_cfg_curr_mod_ext_info &
+	config.phy_type = abilities->phy_type;
+	config.phy_type_ext = abilities->phy_type_ext;
+	config.link_speed = abilities->link_speed;
+	config.eee_capability = abilities->eee_capability;
+	config.eeer = abilities->eeer_val;
+	config.low_power_ctrl = abilities->d3_lpan;
+	config.fec_config = abilities->fec_cfg_curr_mod_ext_info &
 			    I40E_AQ_PHY_FEC_CONFIG_MASK;
-		status = i40e_aq_set_phy_config(hw, &config, NULL);
 
+	return i40e_aq_set_phy_config(hw, &config, NULL);
+}
+
+/**
+ * i40e_set_fc
+ * @hw: pointer to the hw struct
+ * @aq_failures: buffer to return AdminQ failure information
+ * @atomic_restart: whether to enable atomic link restart
+ *
+ * Set the requested flow control mode using set_phy_config.
+ **/
+enum i40e_status_code i40e_set_fc(struct i40e_hw *hw, u8 *aq_failures,
+				  bool atomic_restart)
+{
+	struct i40e_aq_get_phy_abilities_resp abilities;
+	enum i40e_status_code status;
+
+	*aq_failures = 0x0;
+
+	/* Get the current phy config */
+	status = i40e_aq_get_phy_capabilities(hw, false, false, &abilities,
+					      NULL);
+	if (status) {
+		*aq_failures |= I40E_SET_FC_AQ_FAIL_GET;
+		return status;
+	}
+
+	status = i40e_set_fc_status(hw, &abilities, atomic_restart);
 	if (status)
 		*aq_failures |= I40E_SET_FC_AQ_FAIL_SET;
-	}
+
 	/* Update the link info */
 	status = i40e_update_link_info(hw);
 	if (status) {
@@ -2537,7 +2548,7 @@ i40e_status i40e_get_link_status(struct i40e_hw *hw, bool *link_up)
  * i40e_updatelink_status - update status of the HW network link
  * @hw: pointer to the hw struct
  **/
-i40e_status i40e_update_link_info(struct i40e_hw *hw)
+noinline_for_stack i40e_status i40e_update_link_info(struct i40e_hw *hw)
 {
 	struct i40e_aq_get_phy_abilities_resp abilities;
 	i40e_status status = 0;