[PATCH v2] dmaengine: dw-edma: Fix multiple times setting of the CYCLE_STATE and CYCLE_BIT bits for HDMA.

[LUO Haowen]

Others have submitted this issue (https://lore.kernel.org/dmaengine/
20240722030405.3385-1-zhengdongxiong@xxxxxxxxxx/), 
but it has not been fixed yet. Therefore, more supplementary information 
is provided here.

As mentioned in the "PCS-CCS-CB-TCB" Producer-Consumer Synchronization of
"DesignWare Cores PCI Express Controller Databook, version 6.00a":

1. The Consumer CYCLE_STATE (CCS) bit in the register only needs to be 
initialized once; the value will update automatically to be 
~CYCLE_BIT (CB) in the next chunk.
2. The Consumer CYCLE_BIT bit in the register is loaded from the LL 
element and tested against CCS. When CB = CCS, the data transfer is 
executed. Otherwise not.

The current logic sets customer (HDMA) CS and CB bits to 1 in each chunk
while setting the producer (software) CB of odd chunks to 0 and even 
chunks to 1 in the linked list. This is leading to a mismatch between 
the producer CB and consumer CS bits.

This issue can be reproduced by setting the transmission data size to
exceed one chunk. By the way, in the EDMA using the same "PCS-CCS-CB-TCB"
mechanism, the CS bit is only initialized once and this issue was not 
found. Refer to 
drivers/dma/dw-edma/dw-edma-v0-core.c:dw_edma_v0_core_start.

So fix this issue by initializing the CYCLE_STATE and CYCLE_BIT bits 
only once.

Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
Signed-off-by: LUO Haowen <luo-hw@xxxxxxxxxxx>
---
v2:
- Add Fixes tag as suggested by maintainer

 drivers/dma/dw-edma/dw-hdma-v0-core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
index e3f8db4fe..ce8f7254b 100644
--- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
+++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
@@ -252,10 +252,10 @@ static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
 			  lower_32_bits(chunk->ll_region.paddr));
 		SET_CH_32(dw, chan->dir, chan->id, llp.msb,
 			  upper_32_bits(chunk->ll_region.paddr));
+		/* Set consumer cycle */
+		SET_CH_32(dw, chan->dir, chan->id, cycle_sync,
+			HDMA_V0_CONSUMER_CYCLE_STAT | HDMA_V0_CONSUMER_CYCLE_BIT);
 	}
-	/* 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);
 
-- 
2.34.1