This is a note to let you know that I've just added the patch titled
dmaengine: dw-edma: HDMA: Add sync read before starting the DMA transfer in remote setup
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
dmaengine-dw-edma-hdma-add-sync-read-before-starting.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 385df4f2a0a36f210f77139bf5599b80259dc786
Author: Kory Maincent <kory.maincent@xxxxxxxxxxx>
Date: Mon Jan 29 17:26:01 2024 +0100
dmaengine: dw-edma: HDMA: Add sync read before starting the DMA transfer in remote setup
[ Upstream commit 712a92a48158e02155b4b6b21e03a817f78c9b7e ]
The Linked list element and pointer are not stored in the same memory as
the HDMA controller register. If the doorbell register is toggled before
the full write of the linked list a race condition error will occur.
In remote setup we can only use a readl to the memory to assure the full
write has occurred.
Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
Reviewed-by: Serge Semin <fancer.lancer@xxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Signed-off-by: Kory Maincent <kory.maincent@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240129-b4-feature_hdma_mainline-v7-5-8e8c1acb7a46@xxxxxxxxxxx
Signed-off-by: Vinod Koul <vkoul@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
index 04b0bcb6ded97..10e8f0715114f 100644
--- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
@@ -222,6 +222,20 @@ static void dw_hdma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
dw_hdma_v0_write_ll_link(chunk, i, control, chunk->ll_region.paddr);
}
+static void dw_hdma_v0_sync_ll_data(struct dw_edma_chunk *chunk)
+{
+ /*
+ * In case of remote HDMA engine setup, the DW PCIe RP/EP internal
+ * configuration registers and application memory are normally accessed
+ * over different buses. Ensure LL-data reaches the memory before the
+ * doorbell register is toggled by issuing the dummy-read from the remote
+ * LL memory in a hope that the MRd TLP will return only after the
+ * last MWr TLP is completed
+ */
+ if (!(chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
+ readl(chunk->ll_region.vaddr.io);
+}
+
static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
{
struct dw_edma_chan *chan = chunk->chan;
@@ -252,6 +266,9 @@ static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
/* Set consumer cycle */
SET_CH_32(dw, chan->dir, chan->id, cycle_sync,
HDMA_V0_CONSUMER_CYCLE_STAT | HDMA_V0_CONSUMER_CYCLE_BIT);
+
+ dw_hdma_v0_sync_ll_data(chunk);
+
/* Doorbell */
SET_CH_32(dw, chan->dir, chan->id, doorbell, HDMA_V0_DOORBELL_START);
}
