net: stmmac: fix LPI transitioning for dwmac4

The LPI transitioning logic in stmmac_main uses
priv->tx_path_in_lpi_mode to enter/exit LPI.

However, priv->tx_path_in_lpi_mode is assigned
using the return value from host_irq_status().

So for dwmac4, priv->tx_path_in_lpi_mode was always false,
so stmmac_tx_clean() would always try to put us in eee mode,
and stmmac_xmit() would never take us out of eee mode.

To fix this, make host_irq_status() read and return the LPI
irq status also for dwmac4.

This also increments the existing LPI counters, so that
ethtool --statistics shows LPI transitions also for dwmac4.

For dwmac1000, irqs are enabled/disabled using the register
named "Interrupt Mask Register", and thus setting a bit disables
that specific irq.

For dwmac4 the matching register is named "MAC_Interrupt_Enable",
and thus setting a bit enables that specific irq.

Looking at dwmac1000_core.c, the irqs that are always enabled are:
LPI and PMT.

Looking at dwmac4_core.c, the irqs that are always enabled are:
PMT.

To be able to read the LPI irq status, we need to enable the LPI
irq also for dwmac4.

Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac4.h

@@ -98,7 +98,7 @@
 #define	GMAC_PCS_IRQ_DEFAULT	(GMAC_INT_RGSMIIS | GMAC_INT_PCS_LINK |	\
 				 GMAC_INT_PCS_ANE)
 
-#define	GMAC_INT_DEFAULT_MASK	GMAC_INT_PMT_EN
+#define	GMAC_INT_DEFAULT_MASK	(GMAC_INT_PMT_EN | GMAC_INT_LPI_EN)
 
 enum dwmac4_irq_status {
 	time_stamp_irq = 0x00001000,
@@ -106,6 +106,7 @@ enum dwmac4_irq_status {
 	mmc_tx_irq = 0x00000400,
 	mmc_rx_irq = 0x00000200,
 	mmc_irq = 0x00000100,
+	lpi_irq = 0x00000020,
 	pmt_irq = 0x00000010,
 };
 
@@ -132,6 +133,10 @@ enum power_event {
 #define GMAC4_LPI_CTRL_STATUS_LPITXA	BIT(19)	/* Enable LPI TX Automate */
 #define GMAC4_LPI_CTRL_STATUS_PLS	BIT(17) /* PHY Link Status */
 #define GMAC4_LPI_CTRL_STATUS_LPIEN	BIT(16)	/* LPI Enable */
+#define GMAC4_LPI_CTRL_STATUS_RLPIEX	BIT(3) /* Receive LPI Exit */
+#define GMAC4_LPI_CTRL_STATUS_RLPIEN	BIT(2) /* Receive LPI Entry */
+#define GMAC4_LPI_CTRL_STATUS_TLPIEX	BIT(1) /* Transmit LPI Exit */
+#define GMAC4_LPI_CTRL_STATUS_TLPIEN	BIT(0) /* Transmit LPI Entry */
 
 /* MAC Debug bitmap */
 #define GMAC_DEBUG_TFCSTS_MASK		GENMASK(18, 17)