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Date: Tue, 03 Apr 2012 14:29:16 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: Mike Sinkovsky <msink@...monline.ru> Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v6 0/2] Ethernet drivers for WIZnet chips On Tue, 2012-04-03 at 18:15 +0600, Mike Sinkovsky wrote: > 03.04.2012 17:39, Eric Dumazet написал: > > On Tue, 2012-04-03 at 16:58 +0600, Mike Sinkovsky wrote: > >> Based on original driver from chip manufacturer, but nearly full rewite. > >> Tested and used in production with Blackfin BF531 embedded processor. > >> > >> Signed-off-by: Mike Sinkovsky<msink@...monline.ru> > >> --- > >> v6: > >> - remove (S0_TX_FSR< skb->len) check in TX handler, it doesn't work > >> anyway. Chip can transmit only one frame with MTU 1500 at a time, > >> and tx buffer size is bigger. > > > > So what happens if XXX frames are given to start_xmit() in a flood ? > > > > You removed any flow control, how can this work ? > > > > Device has an infinite queue ? > > As I understand from datasheet, device doesn't have tx queue at all. > It have tx buffer, processor must save transmitted frame to it, and then > save SEND command to command register. When transmission completed, > SENDOK bit in interrupt register will be set to '1', and interrupt > handler will be called. > > So, according to datasheet, driver must stop queue in start_xmit() > routine, and wake in interrupt handler of SENDOK bit. > I tried this, and it basically works, but SOMETIMES, very rare, I see > tx_timeout(). > > And without any flow control - driver works perfectly. > Weird, don't know why. Really this should be fixed, since your driver makes qdisc flow control impossible (unless adding a rate limiter like HTB/CBQ) You probably had a race on your xmit routine, and interrupt routine. You need proper synchronization : A spinlock to make this easy, or a smart barrier game. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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