linux-kernel - [PATCH 1/2] dmaengine: ti: k3-udma: Respond TX done if DMA_PREP

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Date:   Mon, 22 Aug 2022 14:45:30 +0530
From:   Vaishnav Achath <vaishnav.a@...com>
To:     <peter.ujfalusi@...il.com>, <vkoul@...nel.org>,
        <broonie@...nel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-spi@...r.kernel.org>
CC:     <vigneshr@...com>, <kishon@...com>, <vaishnav.a@...com>
Subject: [PATCH 1/2] dmaengine: ti: k3-udma: Respond TX done if DMA_PREP_INTERRUPT is not requested

When the DMA consumer driver does not expect the callback for TX done,
There is no need to perform the channel RT byte counter calculations 
and estimate the completion but return complete on first attempt itself.
This assumes that the consumer who did not request DMA_PREP_INTERRUPT 
has its own mechanism for understanding TX completion, example: MCSPI
EOW interrupt can be used as TX completion signal for a SPI transaction.

Signed-off-by: Vaishnav Achath <vaishnav.a@...com>
---
 drivers/dma/ti/k3-udma.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
index 39b330ada200..03d579068453 100644
--- a/drivers/dma/ti/k3-udma.c
+++ b/drivers/dma/ti/k3-udma.c
@@ -263,6 +263,7 @@ struct udma_chan_config {
 	enum udma_tp_level channel_tpl; /* Channel Throughput Level */
 
 	u32 tr_trigger_type;
+	unsigned long tx_flags;
 
 	/* PKDMA mapped channel */
 	int mapped_channel_id;
@@ -1057,7 +1058,7 @@ static bool udma_is_desc_really_done(struct udma_chan *uc, struct udma_desc *d)
 
 	/* Only TX towards PDMA is affected */
 	if (uc->config.ep_type == PSIL_EP_NATIVE ||
-	    uc->config.dir != DMA_MEM_TO_DEV)
+	    uc->config.dir != DMA_MEM_TO_DEV || !(uc->config.tx_flags & DMA_PREP_INTERRUPT))
 		return true;
 
 	peer_bcnt = udma_tchanrt_read(uc, UDMA_CHAN_RT_PEER_BCNT_REG);
@@ -3418,6 +3419,8 @@ udma_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	if (!burst)
 		burst = 1;
 
+	uc->config.tx_flags = tx_flags;
+
 	if (uc->config.pkt_mode)
 		d = udma_prep_slave_sg_pkt(uc, sgl, sglen, dir, tx_flags,
 					   context);
-- 
2.17.1