netdev - Re: 82557/8/9 Ethernet Pro 100 interrupt mitigation support

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Date:	Mon, 03 Sep 2007 15:09:34 +0200
From:	John Sigler <linux.kernel@...e.fr>
To:	John Sigler <linux.kernel@...e.fr>
CC:	netdev@...r.kernel.org, linux-net@...r.kernel.org,
	linux.nics@...el.com, e1000-devel@...ts.sourceforge.net
Subject: Re: 82557/8/9 Ethernet Pro 100 interrupt mitigation support

John Sigler wrote:

> I have several systems with three integrated Intel 82559 (I *think*).
> 
> Does someone know if these boards support hardware interrupt mitigation?
> I.e. is it possible to configure them to raise an IRQ only if their
> hardware buffer is full OR if some given time (say 1 ms) has passed and
> packets are available in their hardware buffer.
> 
> I've been using the eepro100 driver up to now, but I'm about to try the
> e100 driver. Would I have to use NAPI? Or is this an orthogonal feature?
> 
> 00:08.0 Ethernet controller: Intel Corporation 82557/8/9 Ethernet Pro 100 (rev 08)
> 	Subsystem: Intel Corporation EtherExpress PRO/100B (TX)
> 	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
> 	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
> 	Latency: 32 (2000ns min, 14000ns max), Cache Line Size: 32 bytes
> 	Interrupt: pin A routed to IRQ 10
> 	Region 0: Memory at e6400000 (32-bit, non-prefetchable) [size=4K]
> 	Region 1: I/O ports at d800 [size=64]
> 	Region 2: Memory at e6100000 (32-bit, non-prefetchable) [size=1M]
> 	Capabilities: [dc] Power Management version 2
> 		Flags: PMEClk- DSI+ D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
> 		Status: D0 PME-Enable- DSel=0 DScale=2 PME-
> 
> 00:09.0 Ethernet controller: Intel Corporation 82557/8/9 Ethernet Pro 100 (rev 08)
> 	Subsystem: Intel Corporation EtherExpress PRO/100B (TX)
> 	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
> 	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
> 	Latency: 32 (2000ns min, 14000ns max), Cache Line Size: 32 bytes
> 	Interrupt: pin A routed to IRQ 11
> 	Region 0: Memory at e6403000 (32-bit, non-prefetchable) [size=4K]
> 	Region 1: I/O ports at dc00 [size=64]
> 	Region 2: Memory at e6200000 (32-bit, non-prefetchable) [size=1M]
> 	Capabilities: [dc] Power Management version 2
> 		Flags: PMEClk- DSI+ D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
> 		Status: D0 PME-Enable- DSel=0 DScale=2 PME-
> 
> 00:0a.0 Ethernet controller: Intel Corporation 82557/8/9 Ethernet Pro 100 (rev 08)
> 	Subsystem: Intel Corporation EtherExpress PRO/100B (TX)
> 	Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B-
> 	Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR-
> 	Latency: 32 (2000ns min, 14000ns max), Cache Line Size: 32 bytes
> 	Interrupt: pin A routed to IRQ 12
> 	Region 0: Memory at e6402000 (32-bit, non-prefetchable) [size=4K]
> 	Region 1: I/O ports at e000 [size=64]
> 	Region 2: Memory at e6000000 (32-bit, non-prefetchable) [size=1M]
> 	Capabilities: [dc] Power Management version 2
> 		Flags: PMEClk- DSI+ D1+ D2+ AuxCurrent=0mA PME(D0+,D1+,D2+,D3hot+,D3cold+)
> 		Status: D0 PME-Enable- DSel=0 DScale=2 PME-

Here is Intel's page for the 82559:
http://www.intel.com/design/network/products/lan/controllers/82559.htm

The "82559ER Fast Ethernet PCI Controller" data sheet mentions a 3 KB 
receive FIFO. I suppose that's too small to aggregate several frames?

The "8255x Controller Family Open Source Software Developer Manual" 
mentions the features supported by the 82559. I don't see anything 
related to interrupt mitigation support.

Does NAPI work well when there is no hardware interrupt mitigation support?

Regards.
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