Date: Tue, 10 Oct 2023 20:28:43 +0200 From: Emmanuel Vadot <manu@bidouilliste.com> To: John Baldwin <jhb@FreeBSD.org> Cc: Emmanuel Vadot <manu@FreeBSD.org>, src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: Re: git: 38cbdae33b7c - main - dwc: Rewrite barrier part Message-ID: <20231010202843.705a2397da1464dec32813d3@bidouilliste.com> In-Reply-To: <0d8a9a3f-d1d0-b5ee-b50f-49eb3888f68e@FreeBSD.org> References: <202310061706.396H63in060807@gitrepo.freebsd.org> <0d8a9a3f-d1d0-b5ee-b50f-49eb3888f68e@FreeBSD.org>
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On Tue, 10 Oct 2023 11:21:21 -0700 John Baldwin <jhb@FreeBSD.org> wrote: > On 10/6/23 1:06 PM, Emmanuel Vadot wrote: > > The branch main has been updated by manu: > > > > URL: https://cgit.FreeBSD.org/src/commit/?id=38cbdae33b7c3f772845c06f52b86c0ddeab6a17 > > > > commit 38cbdae33b7c3f772845c06f52b86c0ddeab6a17 > > Author: Emmanuel Vadot <manu@FreeBSD.org> > > AuthorDate: 2023-10-06 16:04:49 +0000 > > Commit: Emmanuel Vadot <manu@FreeBSD.org> > > CommitDate: 2023-10-06 17:05:45 +0000 > > > > dwc: Rewrite barrier part > > > > We only need a barrier after writing the OWN bit so everything is > > coherent for the DMA engine. > > --- > > sys/dev/dwc/dwc1000_dma.c | 3 --- > > 1 file changed, 3 deletions(-) > > > > diff --git a/sys/dev/dwc/dwc1000_dma.c b/sys/dev/dwc/dwc1000_dma.c > > index f6baa0bd3e45..4f8ae088305a 100644 > > --- a/sys/dev/dwc/dwc1000_dma.c > > +++ b/sys/dev/dwc/dwc1000_dma.c > > @@ -216,7 +216,6 @@ txdesc_setup(struct dwc_softc *sc, int idx, bus_addr_t paddr, > > sc->txdesc_ring[idx].addr1 = (uint32_t)(paddr); > > sc->txdesc_ring[idx].desc0 = desc0; > > sc->txdesc_ring[idx].desc1 = desc1; > > - wmb(); > > sc->txdesc_ring[idx].desc0 |= TDESC0_OWN; > > wmb(); > > } > > @@ -237,7 +236,6 @@ rxdesc_setup(struct dwc_softc *sc, int idx, bus_addr_t paddr) > > sc->rxdesc_ring[idx].desc1 = ERDESC1_RCH | > > MIN(MCLBYTES, ERDESC1_RBS1_MASK); > > > > - wmb(); > > sc->rxdesc_ring[idx].desc0 = RDESC0_OWN; > > wmb(); > > return (nidx); > > @@ -524,7 +522,6 @@ dma1000_rxfinish_locked(struct dwc_softc *sc) > > > > m = dwc_rxfinish_one(sc, desc, sc->rxbuf_map + idx); > > if (m == NULL) { > > - wmb(); > > desc->desc0 = RDESC0_OWN; > > wmb(); > > } else { > > Hmm, are you sure? I suspect you removed the wrong barrier here. You want the > other writes to update other fields in the desc to post before the write that > sets TDESC0_OWN. The barrier after TDESC0_OWN is useless, but the one you removed > is probably the one that matters. In particular you don't want TDESC0_OWN to be > set when other writes (e.g. setting desc1) are not yet visible. > > -- > John Baldwin > Yeah what you say make sense, the thing is on all the platform I have I've never needed the barrier so it was hard to test for me what was really needed, but you explanation make sense and I'll change the code. Thanks. Cheers, -- Emmanuel Vadot <manu@bidouilliste.com> <manu@freebsd.org>
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