On Wed, Feb 15, 2017 at 12:13 PM, Dan Williams [off-list ref] wrote:

On Tue, Feb 14, 2017 at 10:25 PM, Anup Patel [off-list ref] wrote:

quoted

On Tue, Feb 14, 2017 at 10:04 PM, Dan Williams [off-list ref] wrote:

quoted

On Mon, Feb 13, 2017 at 10:51 PM, Anup Patel [off-list ref] wrote:

quoted

The Broadcom stream buffer accelerator (SBA) provides offloading
capabilities for RAID operations. This SBA offload engine is
accessible via Broadcom SoC specific ring manager.

This patch adds Broadcom SBA RAID driver which provides one
DMA device with RAID capabilities using one or more Broadcom
SoC specific ring manager channels. The SBA RAID driver in its
current shape implements memcpy, xor, and pq operations.

Signed-off-by: Anup Patel <redacted>
Reviewed-by: Ray Jui <redacted>
---
 drivers/dma/Kconfig        |   13 +
 drivers/dma/Makefile       |    1 +
 drivers/dma/bcm-sba-raid.c | 1694 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1708 insertions(+)
 create mode 100644 drivers/dma/bcm-sba-raid.c

diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 263495d..bf8fb84 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig

@@ -99,6 +99,19 @@ config AXI_DMAC
          controller is often used in Analog Device's reference designs for FPGA
          platforms.

+config BCM_SBA_RAID
+       tristate "Broadcom SBA RAID engine support"
+       depends on (ARM64 && MAILBOX && RAID6_PQ) || COMPILE_TEST
+       select DMA_ENGINE
+       select DMA_ENGINE_RAID
+       select ASYNC_TX_ENABLE_CHANNEL_SWITCH

I thought you agreed to drop this. Its usage is broken.

If ASYNC_TX_ENABLE_CHANNEL_SWITCH is not selected
then async_dma_find_channel() will only try to find channel
with DMA_ASYNC_TX capability.

The DMA_ASYNC_TX capability is set by
dma_async_device_register() when all Async Tx
capabilities are supported by a DMA devices namely
DMA_INTERRUPT, DMA_MEMCPY, DMA_XOR,
DMA_XOR_VAL, DMA_PQ, and DMA_PQ_VAL.

We only support DMA_MEMCPY, DMA_XOR, and
DMA_PQ capabilities in BCM-SBA-RAID driver so
DMA_ASYNC_TX capability is never set for the
DMA device registered by BCM-SBA-RAID driver.

Due to above, if ASYNC_TX_ENABLE_CHANNEL_SWITCH
is not selected then Async Tx APIs fail to find DMA
channel provided by BCM-SBA-RAID hence the
option ASYNC_TX_ENABLE_CHANNEL_SWITCH is
required for BCM-SBA-RAID.

The DMA mappings are violated by channel switching
only if we switch form DMA channel A to DMA channel
B and both these DMA channels have different underlying
"struct device". In most of the cases DMA mappings
are not violated because DMA channels having
Async Tx capabilities are provided using same
underlying "struct device".

No, fix the infrastructure. Do not put local hack in your driver for
this global problem [1].

There is no hack in the driver. We need
ASYNC_TX_ENABLE_CHANNEL_SWITCH
based on current state of dmaengine framework.

The framework should be fixed as separate patchset.

We have other RAID drivers such as xgene-dma and
mv_xor_v2 who also require
ASYNC_TX_ENABLE_CHANNEL_SWITCH due
to same reason.

Fixing the framework and improving framework is
a ongoing process. I don't see why that should
stop this patchset.

Regards,
Anup