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authorDan Williams <dan.j.williams@intel.com>2017-02-15 18:42:09 -0800
committerVinod Koul <vinod.koul@intel.com>2017-02-16 10:08:41 +0530
commitb802c8410ca915e7772e738e68420115f1a3c811 (patch)
tree0d793dbc2f21ba6ed753facd4eeee7822cb1f145 /include/linux/async_tx.h
parentdc312349e87526dfe6387c1a82fafded706f0572 (diff)
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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.h2
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
/**