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Subject[PATCH 7/8] async_tx: build-time toggling of async_{syndrome, xor}_val dma support
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ioat3.2 does not support asynchronous error notifications which makes
the driver experience latencies when non-zero pq validate results are
expected. Provide a mechanism for turning off async_xor_val and
async_syndrome_val via Kconfig. This approach is generally useful for
any driver that specifies ASYNC_TX_DISABLE_CHANNEL_SWITCH and would like
to force the async_tx api to fall back to the synchronous path for
certain operations.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
crypto/async_tx/Kconfig | 5 +++++
crypto/async_tx/async_pq.c | 14 +++++++++++---
crypto/async_tx/async_xor.c | 15 ++++++++++++---
drivers/dma/Kconfig | 2 ++
drivers/dma/dmaengine.c | 6 ++++++
drivers/dma/ioat/dma_v3.c | 10 ++++++++++
6 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/crypto/async_tx/Kconfig b/crypto/async_tx/Kconfig
index e5aeb2b..e28e276 100644
--- a/crypto/async_tx/Kconfig
+++ b/crypto/async_tx/Kconfig
@@ -23,3 +23,8 @@ config ASYNC_RAID6_RECOV
select ASYNC_CORE
select ASYNC_PQ

+config ASYNC_TX_DISABLE_PQ_VAL_DMA
+ bool
+
+config ASYNC_TX_DISABLE_XOR_VAL_DMA
+ bool
diff --git a/crypto/async_tx/async_pq.c b/crypto/async_tx/async_pq.c
index 6b5cc4f..ec87f53 100644
--- a/crypto/async_tx/async_pq.c
+++ b/crypto/async_tx/async_pq.c
@@ -240,6 +240,16 @@ async_gen_syndrome(struct page **blocks, unsigned int offset, int disks,
}
EXPORT_SYMBOL_GPL(async_gen_syndrome);

+static inline struct dma_chan *
+pq_val_chan(struct async_submit_ctl *submit, struct page **blocks, int disks, size_t len)
+{
+ #ifdef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
+ return NULL;
+ #endif
+ return async_tx_find_channel(submit, DMA_PQ_VAL, NULL, 0, blocks,
+ disks, len);
+}
+
/**
* async_syndrome_val - asynchronously validate a raid6 syndrome
* @blocks: source blocks from idx 0..disks-3, P @ disks-2 and Q @ disks-1
@@ -260,9 +270,7 @@ async_syndrome_val(struct page **blocks, unsigned int offset, int disks,
size_t len, enum sum_check_flags *pqres, struct page *spare,
struct async_submit_ctl *submit)
{
- struct dma_chan *chan = async_tx_find_channel(submit, DMA_PQ_VAL,
- NULL, 0, blocks, disks,
- len);
+ struct dma_chan *chan = pq_val_chan(submit, blocks, disks, len);
struct dma_device *device = chan ? chan->device : NULL;
struct dma_async_tx_descriptor *tx;
unsigned char coefs[disks-2];
diff --git a/crypto/async_tx/async_xor.c b/crypto/async_tx/async_xor.c
index 79182dc..079ae8c 100644
--- a/crypto/async_tx/async_xor.c
+++ b/crypto/async_tx/async_xor.c
@@ -234,6 +234,17 @@ static int page_is_zero(struct page *p, unsigned int offset, size_t len)
memcmp(a, a + 4, len - 4) == 0);
}

+static inline struct dma_chan *
+xor_val_chan(struct async_submit_ctl *submit, struct page *dest,
+ struct page **src_list, int src_cnt, size_t len)
+{
+ #ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
+ return NULL;
+ #endif
+ return async_tx_find_channel(submit, DMA_XOR_VAL, &dest, 1, src_list,
+ src_cnt, len);
+}
+
/**
* async_xor_val - attempt a xor parity check with a dma engine.
* @dest: destination page used if the xor is performed synchronously
@@ -255,9 +266,7 @@ async_xor_val(struct page *dest, struct page **src_list, unsigned int offset,
int src_cnt, size_t len, enum sum_check_flags *result,
struct async_submit_ctl *submit)
{
- struct dma_chan *chan = async_tx_find_channel(submit, DMA_XOR_VAL,
- &dest, 1, src_list,
- src_cnt, len);
+ struct dma_chan *chan = xor_val_chan(submit, dest, src_list, src_cnt, len);
struct dma_device *device = chan ? chan->device : NULL;
struct dma_async_tx_descriptor *tx = NULL;
dma_addr_t *dma_src = NULL;
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 5903a88..b401dad 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -26,6 +26,8 @@ config INTEL_IOATDMA
select DMA_ENGINE
select DCA
select ASYNC_TX_DISABLE_CHANNEL_SWITCH
+ select ASYNC_TX_DISABLE_PQ_VAL_DMA
+ select ASYNC_TX_DISABLE_XOR_VAL_DMA
help
Enable support for the Intel(R) I/OAT DMA engine present
in recent Intel Xeon chipsets.
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index b6442f0..8f99354 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -632,16 +632,22 @@ static bool device_has_all_tx_types(struct dma_device *device)
#if defined(CONFIG_ASYNC_XOR) || defined(CONFIG_ASYNC_XOR_MODULE)
if (!dma_has_cap(DMA_XOR, device->cap_mask))
return false;
+
+ #ifndef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
if (!dma_has_cap(DMA_XOR_VAL, device->cap_mask))
return false;
#endif
+ #endif

#if defined(CONFIG_ASYNC_PQ) || defined(CONFIG_ASYNC_PQ_MODULE)
if (!dma_has_cap(DMA_PQ, device->cap_mask))
return false;
+
+ #ifndef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
if (!dma_has_cap(DMA_PQ_VAL, device->cap_mask))
return false;
#endif
+ #endif

return true;
}
diff --git a/drivers/dma/ioat/dma_v3.c b/drivers/dma/ioat/dma_v3.c
index 252cf2d..189788f 100644
--- a/drivers/dma/ioat/dma_v3.c
+++ b/drivers/dma/ioat/dma_v3.c
@@ -1206,6 +1206,16 @@ int __devinit ioat3_dma_probe(struct ioatdma_device *device, int dca)
device->timer_fn = ioat2_timer_event;
}

+ #ifdef CONFIG_ASYNC_TX_DISABLE_PQ_VAL_DMA
+ dma_cap_clear(DMA_PQ_VAL, dma->cap_mask);
+ dma->device_prep_dma_pq_val = NULL;
+ #endif
+
+ #ifdef CONFIG_ASYNC_TX_DISABLE_XOR_VAL_DMA
+ dma_cap_clear(DMA_XOR_VAL, dma->cap_mask);
+ dma->device_prep_dma_xor_val = NULL;
+ #endif
+
/* -= IOAT ver.3 workarounds =- */
/* Write CHANERRMSK_INT with 3E07h to mask out the errors
* that can cause stability issues for IOAT ver.3


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