netdev - Re: [PATCH (net.git)] stmmac: prevent false carrier sense detection

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Message-Id: <20140829.195539.1489311917586365339.davem@davemloft.net>
Date:	Fri, 29 Aug 2014 19:55:39 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	peppe.cavallaro@...com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH (net.git)] stmmac: prevent false carrier sense detection

From: Giuseppe Cavallaro <peppe.cavallaro@...com>
Date: Wed, 27 Aug 2014 08:20:04 +0200

> This patch is to w/a a problem that happens on some boxes when run at 10Mbps
> Half duplex mode.
> 
> During the transmission the CSR signal is asserted for some time and the frames
> aborted because of carrier sense error.
> This is reported by MMC HW counter: txcarrier signal.
> This actually is a false carrier so the frames are good and there is no reason
> to ask for dropping them.
> 
> This patch so disables the Carrier Sense During Transmission
> and this means that the MAC transmitter ignore the CRS signal
> during frame transmission in Half-Duplex mode.
> 
> Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@...com>
> Acked-by: Vince Bridgers <vbridgers2013@...il.com>
> Acked-by: Ley Foon Tan <lftan@...era.com>
> Acked-by: Chen-Yu Tsai <wens@...e.org>

Applied.

Although it would have made more sense to me if you only set the DCRS bit
in the case where the troubles occur, half-duplex 10Mbps, so that in other
modes real carrier loss during transmit would actually be detected.
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