On Tue, Feb 14, 2017 at 10:25 PM, Anup Patel <anup.patel@xxxxxxxxxxxx> wrote: > On Tue, Feb 14, 2017 at 10:04 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: >> On Mon, Feb 13, 2017 at 10:51 PM, Anup Patel <anup.patel@xxxxxxxxxxxx> wrote: >>> 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 <anup.patel@xxxxxxxxxxxx> >>> Reviewed-by: Ray Jui <ray.jui@xxxxxxxxxxxx> >>> --- >>> 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]. [1]: https://lwn.net/Articles/443531/
