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Subject[PATCH 3/6] async_tx: Handle DMA devices having support for fewer PQ coefficients
Date
The DMAENGINE framework assumes that if PQ offload is supported by a
DMA device then all 256 PQ coefficients are supported. This assumption
does not hold anymore because we now have BCM-SBA-RAID offload engine
which supports PQ offload with limited number of PQ coefficients.

This patch extends async_tx APIs to handle DMA devices with support
for fewer PQ coefficients.

Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
---
crypto/async_tx/async_pq.c | 3 +++
crypto/async_tx/async_raid6_recov.c | 12 ++++++++++--
include/linux/dmaengine.h | 19 +++++++++++++++++++
include/linux/raid/pq.h | 3 +++
4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
index f83de99..16c6526 100644
--- a/crypto/async_tx/async_pq.c
+++ b/crypto/async_tx/async_pq.c
@@ -187,6 +187,9 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,

BUG_ON(disks > 255 || !(P(blocks, disks) || Q(blocks, disks)));

+ if (device && dma_maxpqcoef(device) < src_cnt)
+ device = NULL;
+
if (device)
unmap = dmaengine_get_unmap_data(device->dev, disks, GFP_NOWAIT);

diff --git a/crypto/async_tx/async_raid6_recov.c b/crypto/async_tx/async_raid6_recov.c
index 8fab627..2916f95 100644
--- a/crypto/async_tx/async_raid6_recov.c
+++ b/crypto/async_tx/async_raid6_recov.c
@@ -352,6 +352,7 @@ async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,
{
void *scribble = submit->scribble;
int non_zero_srcs, i;
+ struct dma_chan *chan = async_dma_find_channel(DMA_PQ);

BUG_ON(faila == failb);
if (failb < faila)
@@ -359,12 +360,15 @@ async_raid6_2data_recov(int disks, size_t bytes, int faila, int failb,

pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);

+ if (chan && dma_maxpqcoef(chan->device) < RAID6_PQ_MAX_COEF)
+ chan = NULL;
+
/* if a dma resource is not available or a scribble buffer is not
* available punt to the synchronous path. In the 'dma not
* available' case be sure to use the scribble buffer to
* preserve the content of 'blocks' as the caller intended.
*/
- if (!async_dma_find_channel(DMA_PQ) || !scribble) {
+ if (!chan || !scribble) {
void **ptrs = scribble ? scribble : (void **) blocks;

async_tx_quiesce(&submit->depend_tx);
@@ -432,15 +436,19 @@ async_raid6_datap_recov(int disks, size_t bytes, int faila,
void *scribble = submit->scribble;
int good_srcs, good, i;
struct page *srcs[2];
+ struct dma_chan *chan = async_dma_find_channel(DMA_PQ);

pr_debug("%s: disks: %d len: %zu\n", __func__, disks, bytes);

+ if (chan && dma_maxpqcoef(chan->device) < RAID6_PQ_MAX_COEF)
+ chan = NULL;
+
/* if a dma resource is not available or a scribble buffer is not
* available punt to the synchronous path. In the 'dma not
* available' case be sure to use the scribble buffer to
* preserve the content of 'blocks' as the caller intended.
*/
- if (!async_dma_find_channel(DMA_PQ) || !scribble) {
+ if (!chan || !scribble) {
void **ptrs = scribble ? scribble : (void **) blocks;

async_tx_quiesce(&submit->depend_tx);
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index feee6ec..d938a8b 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -24,6 +24,7 @@
#include <linux/scatterlist.h>
#include <linux/bitmap.h>
#include <linux/types.h>
+#include <linux/raid/pq.h>
#include <asm/page.h>

/**
@@ -668,6 +669,7 @@ struct dma_filter {
* @cap_mask: one or more dma_capability flags
* @max_xor: maximum number of xor sources, 0 if no capability
* @max_pq: maximum number of PQ sources and PQ-continue capability
+ * @max_pqcoef: maximum number of PQ coefficients, 0 if all supported
* @copy_align: alignment shift for memcpy operations
* @xor_align: alignment shift for xor operations
* @pq_align: alignment shift for pq operations
@@ -727,11 +729,13 @@ struct dma_device {
dma_cap_mask_t cap_mask;
unsigned short max_xor;
unsigned short max_pq;
+ unsigned short max_pqcoef;
enum dmaengine_alignment copy_align;
enum dmaengine_alignment xor_align;
enum dmaengine_alignment pq_align;
enum dmaengine_alignment fill_align;
#define DMA_HAS_PQ_CONTINUE (1 << 15)
+ #define DMA_HAS_FEWER_PQ_COEF (1 << 15)

int dev_id;
struct device *dev;
@@ -1122,6 +1126,21 @@ static inline int dma_maxpq(struct dma_device *dma, enum dma_ctrl_flags flags)
BUG();
}

+static inline void dma_set_maxpqcoef(struct dma_device *dma,
+ unsigned short max_pqcoef)
+{
+ if (max_pqcoef < RAID6_PQ_MAX_COEF) {
+ dma->max_pqcoef = max_pqcoef;
+ dma->max_pqcoef |= DMA_HAS_FEWER_PQ_COEF;
+ }
+}
+
+static inline unsigned short dma_maxpqcoef(struct dma_device *dma)
+{
+ return (dma->max_pqcoef & DMA_HAS_FEWER_PQ_COEF) ?
+ (dma->max_pqcoef & ~DMA_HAS_FEWER_PQ_COEF) : RAID6_PQ_MAX_COEF;
+}
+
static inline size_t dmaengine_get_icg(bool inc, bool sgl, size_t icg,
size_t dir_icg)
{
diff --git a/include/linux/raid/pq.h b/include/linux/raid/pq.h
index 30f9453..f3a04bb 100644
--- a/include/linux/raid/pq.h
+++ b/include/linux/raid/pq.h
@@ -15,6 +15,9 @@

#ifdef __KERNEL__

+/* Max number of PQ coefficients */
+#define RAID6_PQ_MAX_COEF 256
+
/* Set to 1 to use kernel-wide empty_zero_page */
#define RAID6_USE_EMPTY_ZERO_PAGE 0
#include <linux/blkdev.h>
--
2.7.4
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