e1000e: Remove duplicated writel() in e1000_configure_tx/rx()

Author: Takamitsu Iwai <takamitz@amazon.co.jp>

Duplicated register initialization codes exist in e1000_configure_tx()
and e1000_configure_rx().

For example, writel(0, tx_ring->head) writes 0 to tx_ring->head, which
is adapter->hw.hw_addr + E1000_TDH(0).

This initialization is already done in ew32(TDH(0), 0).

ew32(TDH(0), 0) is equivalent to __ew32(hw, E1000_TDH(0), 0). It
executes writel(0, hw->hw_addr + E1000_TDH(0)). Since variable hw is
set to &adapter->hw, it is equal to writel(0, tx_ring->head).

We can remove similar four writel() in e1000_configure_tx() and
e1000_configure_rx().

commit 0845d45 ("e1000e: Modify Tx/Rx configurations to avoid
null pointer dereferences in e1000_open") has introduced these
writel(). This commit moved register writing to
e1000_configure_tx/rx(), and as result, it caused duplication in
e1000_configure_tx/rx().

This patch modifies the sequence of register writing, but removing
these writes is safe because the same writes were already there before
the commit.

I also have checked the datasheets [0] [1] and have not found any
description that we need to write RDH, RDT, TDH and TDT registers
twice at initialization. Furthermore, we have tested this patch on an
I219-V device physically.

Link: https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/82577-gbe-phy-datasheet.pdf [0]
Link: https://www.intel.com/content/www/us/en/content-details/613460/intel-82583v-gbe-controller-datasheet.html [1]
Tested-by: Kohei Enju <enjuk@amazon.com>
Signed-off-by: Takamitsu Iwai <takamitz@amazon.co.jp>
Tested-by: Mor Bar-Gabay <morx.bar.gabay@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
(cherry picked from commit 0cab3b0)
JIRA: https://issues.redhat.com/browse/RHEL-99399
Signed-off-by: Corinna Vinschen <vinschen@redhat.com>

Author: github-cygwin

drivers/net/ethernet/intel/e1000e/netdev.c

@@ -2928,11 +2928,8 @@ static void e1000_configure_tx(struct e1000_adapter *adapter)
 	tx_ring->head = adapter->hw.hw_addr + E1000_TDH(0);
 	tx_ring->tail = adapter->hw.hw_addr + E1000_TDT(0);
 
-	writel(0, tx_ring->head);
 	if (adapter->flags2 & FLAG2_PCIM2PCI_ARBITER_WA)
 		e1000e_update_tdt_wa(tx_ring, 0);
-	else
-		writel(0, tx_ring->tail);
 
 	/* Set the Tx Interrupt Delay register */
 	ew32(TIDV, adapter->tx_int_delay);
@@ -3253,11 +3250,8 @@ static void e1000_configure_rx(struct e1000_adapter *adapter)
 	rx_ring->head = adapter->hw.hw_addr + E1000_RDH(0);
 	rx_ring->tail = adapter->hw.hw_addr + E1000_RDT(0);
 
-	writel(0, rx_ring->head);
 	if (adapter->flags2 & FLAG2_PCIM2PCI_ARBITER_WA)
 		e1000e_update_rdt_wa(rx_ring, 0);
-	else
-		writel(0, rx_ring->tail);
 
 	/* Enable Receive Checksum Offload for TCP and UDP */
 	rxcsum = er32(RXCSUM);