Re: ioatdma: add ioat_raid_enabled module parameter

["Jiang, Dave" <dave.jiang@intel.com>]

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I'm ok with enabling this for people that just want to use DMA and not
RAID. 

Acked-by: Dave Jiang <dave.jiang@intel.com>

On Thu, 2013-08-01 at 00:05 +0200, Brice Goglin wrote:
> ioatdma: add ioat_raid_enabled module parameter
> 
> Commit f26df1a1 added a 64-byte alignment requirement for legacy
> operations to work around a silicon errata when mixing legacy and
> RAID descriptors.
> Passing ioat_raid_enabled=0 now disables RAID offload entirely in
> the ioatdma driver so that legacy operations (memcpy, etc.) can
> work without alignment restrictions anymore.
> 
> Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
> ---
>  drivers/dma/ioat/dma_v3.c |    9 +++++++--
>  1 file changed, 7 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	2013-07-31 23:47:54.246719841 +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 (default: 1)");
> +
>  /* 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 (is_xeon_cb32(pdev) && ioat_raid_enabled)
>  		dma->copy_align = 6;
>  
>  	dma_cap_set(DMA_INTERRUPT, dma->cap_mask);
> @@ -1783,7 +1788,7 @@ int ioat3_dma_probe(struct ioatdma_devic
>  
>  	device->cap = readl(device->reg_base + IOAT_DMA_CAP_OFFSET);
>  
> -	if (is_bwd_noraid(pdev))
> +	if (!ioat_raid_enabled || is_bwd_noraid(pdev))
>  		device->cap &= ~(IOAT_CAP_XOR | IOAT_CAP_PQ | IOAT_CAP_RAID16SS);
>  
>  	/* dca is incompatible with raid operations */
> 

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