linux-kernel - [PATCH v3 01/12] dmaengine: at_xdmac: Don't start transactions at tx

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Message-ID: <20211215110115.191749-2-tudor.ambarus@microchip.com>
Date:   Wed, 15 Dec 2021 13:01:04 +0200
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <vkoul@...nel.org>
CC:     <ludovic.desroches@...rochip.com>, <nicolas.ferre@...rochip.com>,
        <mripard@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>
Subject: [PATCH v3 01/12] dmaengine: at_xdmac: Don't start transactions at tx_submit level

tx_submit is supposed to push the current transaction descriptor to a
pending queue, waiting for issue_pending() to be called. issue_pending()
must start the transfer, not tx_submit(), thus remove
at_xdmac_start_xfer() from at_xdmac_tx_submit(). Clients of at_xdmac that
assume that tx_submit() starts the transfer must be updated and call
dma_async_issue_pending() if they miss to call it (one example is
atmel_serial).

As the at_xdmac_start_xfer() is now called only from
at_xdmac_advance_work() when !at_xdmac_chan_is_enabled(), the
at_xdmac_chan_is_enabled() check is no longer needed in
at_xdmac_start_xfer(), thus remove it.

Fixes: e1f7c9eee707 ("dmaengine: at_xdmac: creation of the atmel eXtended DMA Controller driver")
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
---
 drivers/dma/at_xdmac.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index e42dede5b243..4ff12b083136 100644
--- a/drivers/dma/at_xdmac.c
+++ b/drivers/dma/at_xdmac.c
@@ -385,9 +385,6 @@ static void at_xdmac_start_xfer(struct at_xdmac_chan *atchan,
 
 	dev_vdbg(chan2dev(&atchan->chan), "%s: desc 0x%p\n", __func__, first);
 
-	if (at_xdmac_chan_is_enabled(atchan))
-		return;
-
 	/* Set transfer as active to not try to start it again. */
 	first->active_xfer = true;
 
@@ -479,9 +476,6 @@ static dma_cookie_t at_xdmac_tx_submit(struct dma_async_tx_descriptor *tx)
 	dev_vdbg(chan2dev(tx->chan), "%s: atchan 0x%p, add desc 0x%p to xfers_list\n",
 		 __func__, atchan, desc);
 	list_add_tail(&desc->xfer_node, &atchan->xfers_list);
-	if (list_is_singular(&atchan->xfers_list))
-		at_xdmac_start_xfer(atchan, desc);
-
 	spin_unlock_irqrestore(&atchan->lock, irqflags);
 	return cookie;
 }
-- 
2.25.1