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| author | Dan Williams <dan.j.williams@intel.com> | 2017-02-15 18:42:09 -0800 |
|---|---|---|
| committer | Vinod Koul <vinod.koul@intel.com> | 2017-02-16 10:08:41 +0530 |
| commit | b802c8410ca915e7772e738e68420115f1a3c811 (patch) | |
| tree | 0d793dbc2f21ba6ed753facd4eeee7822cb1f145 /include/linux/async_tx.h | |
| parent | dc312349e87526dfe6387c1a82fafded706f0572 (diff) | |
| download | linux-b802c8410ca915e7772e738e68420115f1a3c811.tar.gz linux-b802c8410ca915e7772e738e68420115f1a3c811.tar.bz2 linux-b802c8410ca915e7772e738e68420115f1a3c811.zip | |
async_tx: deprecate broken support for channel switching
Back in 2011, Russell pointed out that the "async_tx channel switch"
capability was violating expectations of the dma mapping api [1]. At the
time the existing uses were reviewed as still usable, but that longer
term we needed a rework of the raid offload implementation. While some
of the framework for a fixed implementation was introduced in 2012 [2],
the wider rewrite never materialized.
There continues to be interest in raid offload with new dma/raid engine
drivers being submitted. Those drivers must not build on top of the
broken channel switching capability.
Prevent async_tx from using an offload engine if the channel switching
capability is enabled. This still allows the engine to be used for other
purposes, but the broken way async_tx uses these engines for raid will
be disabled. For configurations where this causes a performance
regression the only solution is to start the work of eliminating the
async_tx api and moving channel management into the raid code directly
where it can manage marshalling an operation stream between multiple dma
channels.
[1]: http://lists.infradead.org/pipermail/linux-arm-kernel/2011-January/036753.html
[2]: https://lkml.org/lkml/2012/12/6/71
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Anup Patel <anup.patel@broadcom.com>
Cc: Rameshwar Prasad Sahu <rsahu@apm.com>
Cc: Saeed Bishara <saeed.bishara@gmail.com>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reported-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Diffstat (limited to 'include/linux/async_tx.h')
| -rw-r--r-- | include/linux/async_tx.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h index 388574ea38ed..28e3cf1465ab 100644 --- a/include/linux/async_tx.h +++ b/include/linux/async_tx.h @@ -87,7 +87,7 @@ struct async_submit_ctl { void *scribble; }; -#ifdef CONFIG_DMA_ENGINE +#if defined(CONFIG_DMA_ENGINE) && !defined(CONFIG_ASYNC_TX_CHANNEL_SWITCH) #define async_tx_issue_pending_all dma_issue_pending_all /** |