Re: port-arm/54199: arm bus_dmamap_sync assertion failure

[Nick Hudson <nick.hudson%gmx.co.uk@localhost>]

The following reply was made to PR port-arm/54199; it has been noted by GNATS.

From: Nick Hudson <nick.hudson%gmx.co.uk@localhost>
To: gnats-bugs%netbsd.org@localhost, thorpej%netbsd.org@localhost, gnats-admin%netbsd.org@localhost,
 netbsd-bugs%netbsd.org@localhost, thorpej%me.com@localhost
Cc: 
Subject: Re: port-arm/54199: arm bus_dmamap_sync assertion failure
Date: Tue, 14 May 2019 20:03:46 +0100

 On 14/05/2019 14:20, Izumi Tsutsui wrote:
 > The following reply was made to PR port-arm/54199; it has been noted by =
 GNATS.
 >
 > From: Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>
 > To: thorpej%me.com@localhost
 > Cc: gnats-bugs%netbsd.org@localhost, jmcneill%invisible.ca@localhost, tsutsui%ceres.dti.ne@localhost.j=
 p
 > Subject: Re: port-arm/54199: arm bus_dmamap_sync assertion failure
 > Date: Tue, 14 May 2019 22:17:21 +0900
 >
 >   > > I have a question:
 >   > > Is it a valid operation to call bus_dmamap_load(9) and bus_dmamap_=
 sync(9)
 >   > > with dmamap dm_mapsize =3D=3D 0?
 >
 >   > Anyway, I would say that the API should be tolerant of these situati=
 ons...  If dm_mapsize =3D=3D 0, then allow offset =3D=3D 0 and len =3D=3D =
 0.  If dm_mapsize !=3D 0, still allow len =3D=3D 0, while enforcing offset=
  invariants.
 >
 >   I see. Thanks for your comment.
 >   (there are several MD code with such assertions)
 >
 >   > Now, the bigger issue I have with this bug is why did sunxi_emac_int=
 r() result in a zero-length bus_dmamap_sync()?
 
 >
 >   No assertion in PREREAD/PREWRITE but in POST ops after xfers?
 >   With a quick glance, one possible path is failure of
 >   sunxi_emac_setup_rxbuf() in inlined sunxi_emac_rxintr()?
 >
 >   Or, does it still happen even if BUS_DMA_COHERENT is specifed to
 >   bus_dmemem_map(9) for tx/rx descriptor memories?
 >   (i.e. possible race between CPU and DMA on updating descriptors?)
 
 
 Does this help
 
 
 https://github.com/skrll/src/commit/f783c83f2dbed515e6afe6ef7ee0e161181f7a=
 10
 
 
 Nick