linux-kernel - [PATCH v2 1/4] soc: fsl: qmc: Only set completion interrupt when needed

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Message-ID: <badb68a85910e5e6f1094ef3b01805209ac21854.1754993232.git.christophe.leroy@csgroup.eu>
Date: Tue, 12 Aug 2025 12:50:55 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Herve Codina <herve.codina@...tlin.com>,
	Qiang Zhao <qiang.zhao@....com>,
	Shengjiu Wang <shengjiu.wang@...il.com>,
	Xiubo Li <Xiubo.Lee@...il.com>,
	Fabio Estevam <festevam@...il.com>,
	Nicolin Chen <nicoleotsuka@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>,
	Takashi Iwai <tiwai@...e.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linuxppc-dev@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-sound@...r.kernel.org
Subject: [PATCH v2 1/4] soc: fsl: qmc: Only set completion interrupt when needed

When no post-completion processing is expected, don't waste time
handling useless interrupts.

Only set QMC_BD_[R/T]X_I when a completion function is passed in,
and perform seamless completion on submit for interruptless buffers.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v2: Keep the UB flag to mark not completed buffers and seamlessly flag them as completed during next submit.
---
 drivers/soc/fsl/qe/qmc.c | 44 ++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 11 deletions(-)

diff --git a/drivers/soc/fsl/qe/qmc.c b/drivers/soc/fsl/qe/qmc.c
index 36c0ccc06151f..8f76b9a5e385d 100644
--- a/drivers/soc/fsl/qe/qmc.c
+++ b/drivers/soc/fsl/qe/qmc.c
@@ -461,9 +461,16 @@ int qmc_chan_write_submit(struct qmc_chan *chan, dma_addr_t addr, size_t length,
 
 	ctrl = qmc_read16(&bd->cbd_sc);
 	if (ctrl & (QMC_BD_TX_R | QMC_BD_TX_UB)) {
-		/* We are full ... */
-		ret = -EBUSY;
-		goto end;
+		if (!(ctrl & QMC_BD_TX_I) && bd == chan->txbd_done) {
+			if (ctrl & QMC_BD_TX_W)
+				chan->txbd_done = chan->txbds;
+			else
+				chan->txbd_done++;
+		} else {
+			/* We are full ... */
+			ret = -EBUSY;
+			goto end;
+		}
 	}
 
 	qmc_write16(&bd->cbd_datlen, length);
@@ -475,6 +482,10 @@ int qmc_chan_write_submit(struct qmc_chan *chan, dma_addr_t addr, size_t length,
 
 	/* Activate the descriptor */
 	ctrl |= (QMC_BD_TX_R | QMC_BD_TX_UB);
+	if (complete)
+		ctrl |= QMC_BD_TX_I;
+	else
+		ctrl &= ~QMC_BD_TX_I;
 	wmb(); /* Be sure to flush the descriptor before control update */
 	qmc_write16(&bd->cbd_sc, ctrl);
 
@@ -569,9 +580,16 @@ int qmc_chan_read_submit(struct qmc_chan *chan, dma_addr_t addr, size_t length,
 
 	ctrl = qmc_read16(&bd->cbd_sc);
 	if (ctrl & (QMC_BD_RX_E | QMC_BD_RX_UB)) {
-		/* We are full ... */
-		ret = -EBUSY;
-		goto end;
+		if (!(ctrl & QMC_BD_RX_I) && bd == chan->rxbd_done) {
+			if (ctrl & QMC_BD_RX_W)
+				chan->rxbd_done = chan->rxbds;
+			else
+				chan->rxbd_done++;
+		} else {
+			/* We are full ... */
+			ret = -EBUSY;
+			goto end;
+		}
 	}
 
 	qmc_write16(&bd->cbd_datlen, 0); /* data length is updated by the QMC */
@@ -587,6 +605,10 @@ int qmc_chan_read_submit(struct qmc_chan *chan, dma_addr_t addr, size_t length,
 
 	/* Activate the descriptor */
 	ctrl |= (QMC_BD_RX_E | QMC_BD_RX_UB);
+	if (complete)
+		ctrl |= QMC_BD_RX_I;
+	else
+		ctrl &= ~QMC_BD_RX_I;
 	wmb(); /* Be sure to flush data before descriptor activation */
 	qmc_write16(&bd->cbd_sc, ctrl);
 
@@ -1482,19 +1504,19 @@ static int qmc_setup_chan(struct qmc *qmc, struct qmc_chan *chan)
 
 	/* Init Rx BDs and set Wrap bit on last descriptor */
 	BUILD_BUG_ON(QMC_NB_RXBDS == 0);
-	val = QMC_BD_RX_I;
 	for (i = 0; i < QMC_NB_RXBDS; i++) {
 		bd = chan->rxbds + i;
-		qmc_write16(&bd->cbd_sc, val);
+		qmc_write16(&bd->cbd_sc, 0);
 	}
 	bd = chan->rxbds + QMC_NB_RXBDS - 1;
-	qmc_write16(&bd->cbd_sc, val | QMC_BD_RX_W);
+	qmc_write16(&bd->cbd_sc, QMC_BD_RX_W);
 
 	/* Init Tx BDs and set Wrap bit on last descriptor */
 	BUILD_BUG_ON(QMC_NB_TXBDS == 0);
-	val = QMC_BD_TX_I;
 	if (chan->mode == QMC_HDLC)
-		val |= QMC_BD_TX_L | QMC_BD_TX_TC;
+		val = QMC_BD_TX_L | QMC_BD_TX_TC;
+	else
+		val = 0;
 	for (i = 0; i < QMC_NB_TXBDS; i++) {
 		bd = chan->txbds + i;
 		qmc_write16(&bd->cbd_sc, val);
-- 
2.49.0