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

[Christophe Leroy]

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.le...@csgroup.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