linux-kernel - [PATCH v2 01/13] dmaengine: at_xdmac: Don't start transactions at tx

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Date:   Thu, 25 Nov 2021 11:00:16 +0200
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <ludovic.desroches@...rochip.com>, <vkoul@...nel.org>,
        <richard.genoud@...il.com>, <gregkh@...uxfoundation.org>,
        <jirislaby@...nel.org>
CC:     <nicolas.ferre@...rochip.com>, <alexandre.belloni@...tlin.com>,
        <mripard@...nel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-serial@...r.kernel.org>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>
Subject: [PATCH v2 01/13] 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().
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.

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).

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 275a76f188ae..ccf796a3b9f3 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