r8169: enable cfg9346 config register access in atomic context

For disabling ASPM during NAPI poll we'll have to unlock access
to the config registers in atomic context. Other code parts
running with config register access unlocked are partially
longer and can sleep. Add a usage counter to enable parallel
execution of code parts requiring unlocked config registers.

Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -616,6 +616,9 @@ struct rtl8169_private {
 	spinlock_t config25_lock;
 	spinlock_t mac_ocp_lock;
 
+	spinlock_t cfg9346_usage_lock;
+	int cfg9346_usage_count;
+
 	unsigned supports_gmii:1;
 	unsigned aspm_manageable:1;
 	dma_addr_t counters_phys_addr;
@@ -664,12 +667,22 @@ static inline struct device *tp_to_dev(struct rtl8169_private *tp)
 
 static void rtl_lock_config_regs(struct rtl8169_private *tp)
 {
-	RTL_W8(tp, Cfg9346, Cfg9346_Lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&tp->cfg9346_usage_lock, flags);
+	if (!--tp->cfg9346_usage_count)
+		RTL_W8(tp, Cfg9346, Cfg9346_Lock);
+	spin_unlock_irqrestore(&tp->cfg9346_usage_lock, flags);
 }
 
 static void rtl_unlock_config_regs(struct rtl8169_private *tp)
 {
-	RTL_W8(tp, Cfg9346, Cfg9346_Unlock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&tp->cfg9346_usage_lock, flags);
+	if (!tp->cfg9346_usage_count++)
+		RTL_W8(tp, Cfg9346, Cfg9346_Unlock);
+	spin_unlock_irqrestore(&tp->cfg9346_usage_lock, flags);
 }
 
 static void rtl_pci_commit(struct rtl8169_private *tp)
@@ -5229,6 +5242,7 @@ static int rtl_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 	tp->eee_adv = -1;
 	tp->ocp_base = OCP_STD_PHY_BASE;
 
+	spin_lock_init(&tp->cfg9346_usage_lock);
 	spin_lock_init(&tp->config25_lock);
 	spin_lock_init(&tp->mac_ocp_lock);