[PATCH v2 1/3] gianfar: Implement workaround for eTSEC74 erratum
davem at davemloft.net
Thu Jul 1 04:37:13 EST 2010
From: Anton Vorontsov <avorontsov at mvista.com>
Date: Wed, 30 Jun 2010 20:39:12 +0400
> MPC8313ECE says:
> "If MACCFG2[Huge Frame]=0 and the Ethernet controller receives frames
> which are larger than MAXFRM, the controller truncates the frames to
> length MAXFRM and marks RxBD[TR]=1 to indicate the error. The controller
> also erroneously marks RxBD[TR]=1 if the received frame length is MAXFRM
> or MAXFRM-1, even though those frames are not truncated.
> No truncation or truncation error occurs if MACCFG2[Huge Frame]=1."
> There are two options to workaround the issue:
> "1. Set MACCFG2[Huge Frame]=1, so no truncation occurs for invalid large
> frames. Software can determine if a frame is larger than MAXFRM by
> reading RxBD[LG] or RxBD[Data Length].
> 2. Set MAXFRM to 1538 (0x602) instead of the default 1536 (0x600), so
> normal-length frames are not marked as truncated. Software can examine
> RxBD[Data Length] to determine if the frame was larger than MAXFRM-2."
> This patch implements the first workaround option by setting HUGEFRAME
> bit, and gfar_clean_rx_ring() already checks the RxBD[Data Length].
> Signed-off-by: Anton Vorontsov <avorontsov at mvista.com>
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