linux-kernel - [PATCH] dmaengine: ti: k3-udma: Fix teardown timeout for cyclic mode

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Date:   Mon, 21 Aug 2023 16:10:03 +0530
From:   Vignesh Raghavendra <vigneshr@...com>
To:     Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Vinod Koul <vkoul@...nel.org>
CC:     <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-arm-kernel@...ts.infradead.org>, <j-luthra@...com>,
        <j-choudhary@...com>, <francesco@...cini.it>
Subject: [PATCH] dmaengine: ti: k3-udma: Fix teardown timeout for cyclic mode

In cyclic mode, last descriptor needs to have EOP flag set so that
teardown flushes data towards PDMA in case of MEM_TO_DMA.  Else,
operation will not complete successfully leading to spurious timeout on
channel terminate.

Without this terminating aplay cmd outputs false error msg like:
[116.402800] ti-bcdma 485c0100.dma-controller: chan1 teardown timeout!

This doesn't seem to be problem with UDMA-P on J7xx devices (although is
a requirement as per spec) but shows up easily on BCDMA + McASP. Fix
this by setting the appropriate flag

Fixes: 017794739702 ("dmaengine: ti: k3-udma: Initial support for K3 BCDMA")
Suggested-by: Peter Ujfalusi <peter.ujfalusi@...il.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@...com>
---

This complete reimplementation based on learning of HW behavior for problems
reported at
https://lore.kernel.org/linux-arm-kernel/20220215044112.161634-1-vigneshr@ti.com/

 drivers/dma/ti/k3-udma.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
index 30fd2f386f36..02aac7be8d28 100644
--- a/drivers/dma/ti/k3-udma.c
+++ b/drivers/dma/ti/k3-udma.c
@@ -3476,6 +3476,10 @@ udma_prep_dma_cyclic_tr(struct udma_chan *uc, dma_addr_t buf_addr,
 	u16 tr0_cnt0, tr0_cnt1, tr1_cnt0;
 	unsigned int i;
 	int num_tr;
+	u32 period_csf = 0;
+
+	if (uc->config.ep_type == PSIL_EP_PDMA_XY && dir == DMA_MEM_TO_DEV)
+		period_csf = CPPI5_TR_CSF_EOP;
 
 	num_tr = udma_get_tr_counters(period_len, __ffs(buf_addr), &tr0_cnt0,
 				      &tr0_cnt1, &tr1_cnt0);
@@ -3525,8 +3529,10 @@ udma_prep_dma_cyclic_tr(struct udma_chan *uc, dma_addr_t buf_addr,
 		}
 
 		if (!(flags & DMA_PREP_INTERRUPT))
-			cppi5_tr_csf_set(&tr_req[tr_idx].flags,
-					 CPPI5_TR_CSF_SUPR_EVT);
+			period_csf |= CPPI5_TR_CSF_SUPR_EVT;
+
+		if (period_csf)
+			cppi5_tr_csf_set(&tr_req[tr_idx].flags, period_csf);
 
 		period_addr += period_len;
 	}
-- 
2.41.0