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EmbeddedPkg/Lan9118Dxe: use MemoryFence

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When reviewing my LAN9118 driver PCD patch [1], Ard Biesheuvel noted
that most calls to gBS->Stall() in this driver seem to be used to
prevent timing issues between the device updating data and the host
reading the values.  And that replacing most of these calls with a
MemoryFence() would be more robust.

The only exceptions are the stalls that are enclosed inside retry loops:

 - in the AutoNegotiate() function.
   This stall is waiting for the link to negotiate, which may require
   stalling until it is ready.

 - in the Lan9118Initialize() function.
   These two stalls are waiting for devices and time out after a number
   of retries.

 - in the SoftReset() function.
   This stall is inside a loop where the comment states:
   "If time taken exceeds 100us, then there was an error condition"

In these instances, I kept the stall, but also added a MemoryFence().

[1] http://article.gmane.org/gmane.comp.bios.edk2.devel/7389

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
This commit is contained in:
Ryan Harkin
2016-02-09 08:52:32 +00:00
committed by Ard Biesheuvel
parent 7d0f92e8fd
commit a4626006bb
2 changed files with 26 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
EmbeddedPkg/Drivers/Lan9118Dxe/Lan9118Dxe.c
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@@ -307,8 +307,7 @@ SnpInitialize (
// Write the current configuration to the register
MmioWrite32 (LAN9118_PMT_CTRL, PmConf);
gBS->Stall (LAN9118_STALL);
gBS->Stall (LAN9118_STALL);
MemoryFence();
// Configure GPIO and HW
Status = ConfigureHardware (HW_CONF_USE_LEDS, Snp);
@@ -431,7 +430,7 @@ SnpReset (
// Write the current configuration to the register
MmioWrite32 (LAN9118_PMT_CTRL, PmConf);
gBS->Stall (LAN9118_STALL);
MemoryFence();
// Reactivate the LEDs
Status = ConfigureHardware (HW_CONF_USE_LEDS, Snp);
@@ -446,7 +445,7 @@ SnpReset (
HwConf |= HW_CFG_TX_FIFO_SIZE(gTxBuffer); // assign size chosen in SnpInitialize
MmioWrite32 (LAN9118_HW_CFG, HwConf); // Write the conf
gBS->Stall (LAN9118_STALL);
MemoryFence();
}
// Enable the receiver and transmitter and clear their contents
@@ -701,7 +700,7 @@ SnpReceiveFilters (
// Write the options to the MAC_CSR
//
IndirectMACWrite32 (INDIRECT_MAC_INDEX_CR, MacCSRValue);
gBS->Stall (LAN9118_STALL);
MemoryFence();
//
// If we have to retrieve something, start packet reception.