On Wed, Feb 15, 2017 at 12:13 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote: > 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]. 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
