On Mon, Feb 13, 2017 at 2:43 PM, Anup Patel [off-list ref] wrote:

On Fri, Feb 10, 2017 at 11:20 PM, Dan Williams [off-list ref] wrote:

quoted

On Fri, Feb 10, 2017 at 1:07 AM, 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 | 1711 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 1725 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

ASYNC_TX_ENABLE_CHANNEL_SWITCH violates the DMA mapping API and
Russell has warned it's especially problematic on ARM [1].  If you
need channel switching for this offload engine to be useful then you
need to move DMA mapping and channel switching responsibilities to MD
itself.

[1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2011-January/036753.html

Actually driver works fine with/without
ASYNC_TX_ENABLE_CHANNEL_SWITCH enabled
so I am fine with removing dependency on this config option.

I stand corrected.

Previously, when I had tried removing
ASYNC_TX_ENABLE_CHANNEL_SWITCH
from BCM_SBA_RAID config option it worked because other
drivers such xgene-dma and mv_xor_v2 are selecting this option.

The BCM-SBA-RAID driver requires
ASYNC_TX_ENABLE_CHANNEL_SWITCH option

There is no issue reported for
ASYNC_TX_ENABLE_CHANNEL_SWITCH
with ARM64 kernel.

The issue you pointed out was with ARM kernel.

We will have to select
ASYNC_TX_ENABLE_CHANNEL_SWITCH
for BCM-SBA-RAID driver
just like other ARM64 RAID drivers such
as xgene-dma and mv_xor_v2.
(Refer, XGENE_DMA and MV_XOR_V2 options)

Regards,
Anup