On Fri, 2013-08-02 at 16:57 +0000, Dan Williams wrote: > > On 8/2/13 12:34 AM, "Brice Goglin" <brice.gog...@inria.fr> wrote: > > >Le 01/08/2013 19:15, Jiang, Dave a écrit : > >> On Thu, 2013-08-01 at 10:11 -0700, Jon Mason wrote: > >>> On Wed, Jul 31, 2013 at 03:14:07PM -0700, Jiang, Dave wrote: > >>>> I'm ok with enabling this for people that just want to use DMA and not > >>>> RAID. > >>> I might be crazy, but I'd be in favor of disabling the RAID offload by > >>> default on non-Atom platforms. > >>> > >> I suppose. Technically it is disabled starting with 3.10 because of the > >> channel switch issue. I'm ok with this disabled by default for the 3.2 > >> platforms that has broken pq-val. > >> > > > >Here's a patch that may do what you guys are saying. > > > >Brice > > > > > > > >ioatdma: disable RAID by default when buggy and add module param > > > >Commit f26df1a1 added a 64-byte alignment requirement for legacy > >operations to work around a silicon errata when mixing legacy and > >RAID descriptors. > > > >RAID offload is now disabled by default on buggy 3.2 platforms. > >Passing ioat_raid_enabled=1 force-enables it on all platforms > >(previous behavior). > >Passing ioat_raid_enabled=0 force-disables it everywhere. > > > >When RAID offload is disabled, legacy operations (memcpy, etc.) > >can work again without alignment restrictions. > > > >Signed-off-by: Brice Goglin <brice.gog...@inria.fr> > >--- > > drivers/dma/ioat/dma_v3.c | 16 ++++++++++++++-- > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > >Index: b/drivers/dma/ioat/dma_v3.c > >=================================================================== > >--- a/drivers/dma/ioat/dma_v3.c 2013-07-31 23:06:24.163810000 +0200 > >+++ b/drivers/dma/ioat/dma_v3.c 2013-08-02 09:28:51.817037742 +0200 > >@@ -67,6 +67,11 @@ > > #include "dma.h" > > #include "dma_v2.h" > > > >+static int ioat_raid_enabled = -1; > >+module_param(ioat_raid_enabled, int, 0444); > >+MODULE_PARM_DESC(ioat_raid_enabled, > >+ "control support of RAID offload (-1=enabled unless broken > >[default], > >0=disabled, 1=enabled)"); > >+ > > /* ioat hardware assumes at least two sources for raid operations */ > > #define src_cnt_to_sw(x) ((x) + 2) > > #define src_cnt_to_hw(x) ((x) - 2) > >@@ -1775,7 +1780,7 @@ int ioat3_dma_probe(struct ioatdma_devic > > dma->device_alloc_chan_resources = ioat2_alloc_chan_resources; > > dma->device_free_chan_resources = ioat2_free_chan_resources; > > > >- if (is_xeon_cb32(pdev)) > >+ if (ioat_raid_enabled == 1 && is_xeon_cb32(pdev)) > > dma->copy_align = 6; > > Actually we can delete this now because is_xeon_cb32() already effectively > means that raid offload will not be used. > > > > > dma_cap_set(DMA_INTERRUPT, dma->cap_mask); > >@@ -1783,7 +1788,14 @@ int ioat3_dma_probe(struct ioatdma_devic > > > > device->cap = readl(device->reg_base + IOAT_DMA_CAP_OFFSET); > > > >- if (is_bwd_noraid(pdev)) > >+ /* disable RAID if: > >+ * force-disabled by module param, > >+ * or not force-enabled on buggy 3.2 platforms, > >+ * or not actually supported. > >+ */ > >+ if (ioat_raid_enabled == 0 > >+ || (ioat_raid_enabled != 1 && is_xeon_cb32(pdev)) > >+ || is_bwd_noraid(pdev)) > > device->cap &= ~(IOAT_CAP_XOR | IOAT_CAP_PQ | > > IOAT_CAP_RAID16SS); > > > > /* dca is incompatible with raid operations */ > > > > I like Jon¹s suggestion. Just make raid disabled by default on non-atom > platforms. When if a non-atom platform comes along without the previous > restrictions it can add itself to this list. > > So let¹s drop the module parameter and just cleanup the 3.2 support to > reflect the current reality of raid being disabled.
Works for me. Then we won't have to worry about the channel switch mess on 3.2. > > -- > Dan >
