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 0845d45e900c ("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 <[email protected]>
Signed-off-by: Takamitsu Iwai <[email protected]>
---
v1->v2
modify commit message to explain the reason why we can remove these writes
safely.
v1 link
https://lore.kernel.org/netdev/[email protected]/
drivers/net/ethernet/intel/e1000e/netdev.c | 6 ------
1 file changed, 6 deletions(-)
diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c
b/drivers/net/ethernet/intel/e1000e/netdev.c
index da5c59daf8ba..89c57be89c88 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/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);
--
2.40.1
