Re: 5.2-RC oerrs and collisions on dc0

On  5 Jan, Maxime Henrion wrote:
> Don Lewis wrote:
>> I just took a closer look at the busdma diff, and this change to
>> dc_txeof() looks very suspicious:
>> 
>> _at__at_ -2663,7 +2809,7 _at__at_
>>                 if (txstat & DC_TXSTAT_OWN)
>>                         break;
>>  
>> -               if (!(cur_tx->dc_ctl & DC_TXCTL_LASTFRAG) ||
>> +               if (!(cur_tx->dc_ctl & DC_TXCTL_FIRSTFRAG) ||
>>                     cur_tx->dc_ctl & DC_TXCTL_SETUP) {
>>                         if (cur_tx->dc_ctl & DC_TXCTL_SETUP) {
>>                                 /*
>> 
>> The code in the "if" block ends with a "continue" which will cause the
>> error handling code to be skipped if the "if" condition is true.  I'm
>> pretty sure that the error status bits are only set in the last
>> descriptor for the frame, so we want to execute the "continue" unless
>> the DC_TXCTL_LASTFRAG bit is set.
>> 
>> Try reverting this part of the busdma change.
> 
> I think you actually found the culprit, though fixing this is not as
> simple as reverting this line.  I changed the check to
> DC_TXCTL_FIRSTFRAG because that's the descriptor which will have a link
> to the mbuf, while it was previously done for the LASTFRAG descriptor.
> However, I didn't think about the code flow enough it seems.  If you
> don't have a fix for this soon, I should be able to do it pretty easily,
> assuming I find the time.

How about something like the following.  I can't test it because I don't
have the appropriate hardware, but at least it compiles ;-)

Index: sys/pci/if_dc.c
===================================================================
RCS file: /home/ncvs/src/sys/pci/if_dc.c,v
retrieving revision 1.137
diff -u -r1.137 if_dc.c
--- sys/pci/if_dc.c	6 Dec 2003 02:29:31 -0000	1.137
+++ sys/pci/if_dc.c	5 Jan 2004 20:00:04 -0000
_at__at_ -2859,7 +2859,7 _at__at_
 		if (txstat & DC_TXSTAT_OWN)
 			break;
 
-		if (!(ctl & DC_TXCTL_FIRSTFRAG) || ctl & DC_TXCTL_SETUP) {
+		if (!(ctl & DC_TXCTL_LASTFRAG) || ctl & DC_TXCTL_SETUP) {
 			if (ctl & DC_TXCTL_SETUP) {
 				/*
 				 * Yes, the PNIC is so brain damaged
_at__at_ -3262,6 +3262,7 _at__at_
 	sc->dc_cdata.dc_tx_prod = frag;
 	sc->dc_cdata.dc_tx_cnt += nseg;
 	sc->dc_ldata->dc_tx_list[cur].dc_ctl |= htole32(DC_TXCTL_LASTFRAG);
+	sc->dc_cdata.dc_tx_chain[cur] = sc->dc_cdata.dc_tx_mapping;
 	if (sc->dc_flags & DC_TX_INTR_FIRSTFRAG)
 		sc->dc_ldata->dc_tx_list[first].dc_ctl |=
 		    htole32(DC_TXCTL_FINT);
_at__at_ -3311,13 +3312,13 _at__at_
 	 * of fragments or hit the end of the mbuf chain.
 	 */
 	idx = sc->dc_cdata.dc_tx_prod;
+	sc->dc_cdata.dc_tx_mapping = *m_head;
 	error = bus_dmamap_load_mbuf(sc->dc_mtag, sc->dc_cdata.dc_tx_map[idx],
 	    *m_head, dc_dma_map_txbuf, sc, 0);
 	if (error)
 		return (error);
 	if (sc->dc_cdata.dc_tx_err != 0)
 		return (sc->dc_cdata.dc_tx_err); 
-	sc->dc_cdata.dc_tx_chain[idx] = *m_head;
 	bus_dmamap_sync(sc->dc_mtag, sc->dc_cdata.dc_tx_map[idx],
 	    BUS_DMASYNC_PREWRITE);
 	bus_dmamap_sync(sc->dc_ltag, sc->dc_lmap,
Index: sys/pci/if_dcreg.h
===================================================================
RCS file: /home/ncvs/src/sys/pci/if_dcreg.h,v
retrieving revision 1.40
diff -u -r1.40 if_dcreg.h
--- sys/pci/if_dcreg.h	6 Dec 2003 02:29:31 -0000	1.40
+++ sys/pci/if_dcreg.h	5 Jan 2004 19:58:05 -0000
_at__at_ -486,6 +486,7 _at__at_
 struct dc_chain_data {
 	struct mbuf		*dc_rx_chain[DC_RX_LIST_CNT];
 	struct mbuf		*dc_tx_chain[DC_TX_LIST_CNT];
+	struct mbuf		*dc_tx_mapping;
 	bus_dmamap_t		dc_rx_map[DC_RX_LIST_CNT];
 	bus_dmamap_t		dc_tx_map[DC_TX_LIST_CNT];
 	u_int32_t		*dc_sbuf;