linux-kernel - [PATCH v2 02/32] dmaengine: at_hdmac: Don't start transactions at tx

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Message-ID: <20221025090306.297886-3-tudor.ambarus@microchip.com>
Date:   Tue, 25 Oct 2022 12:02:36 +0300
From:   Tudor Ambarus <tudor.ambarus@...rochip.com>
To:     <vkoul@...nel.org>, <peda@...ntia.se>, <du@...ntia.se>
CC:     <maciej.sosnowski@...el.com>, <nicolas.ferre@...rochip.com>,
        <mripard@...nel.org>, <torfl6749@...il.com>,
        <linux-kernel@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        "Tudor Ambarus" <tudor.ambarus@...rochip.com>,
        <stable@...r.kernel.org>
Subject: [PATCH v2 02/32] dmaengine: at_hdmac: 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 atc_dostart() from
atc_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.
The vdbg print was moved to after the lock is released. It is desirable to
do the prints without the lock held if possible, and because the if
statement disappears there's no reason why to do the print while holding
the lock.

Fixes: dc78baa2b90b ("dmaengine: at_hdmac: new driver for the Atmel AHB DMA Controller")
Reported-by: Peter Rosin <peda@...ntia.se>
Signed-off-by: Tudor Ambarus <tudor.ambarus@...rochip.com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/lkml/13c6c9a2-6db5-c3bf-349b-4c127ad3496a@axentia.se/
---
 drivers/dma/at_hdmac.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/at_hdmac.c b/drivers/dma/at_hdmac.c
index 5a50423b7378..3f71f4d2f467 100644
--- a/drivers/dma/at_hdmac.c
+++ b/drivers/dma/at_hdmac.c
@@ -691,19 +691,11 @@ static dma_cookie_t atc_tx_submit(struct dma_async_tx_descriptor *tx)
 	spin_lock_irqsave(&atchan->lock, flags);
 	cookie = dma_cookie_assign(tx);
 
-	if (list_empty(&atchan->active_list)) {
-		dev_vdbg(chan2dev(tx->chan), "tx_submit: started %u\n",
-				desc->txd.cookie);
-		atc_dostart(atchan, desc);
-		list_add_tail(&desc->desc_node, &atchan->active_list);
-	} else {
-		dev_vdbg(chan2dev(tx->chan), "tx_submit: queued %u\n",
-				desc->txd.cookie);
-		list_add_tail(&desc->desc_node, &atchan->queue);
-	}
-
+	list_add_tail(&desc->desc_node, &atchan->queue);
 	spin_unlock_irqrestore(&atchan->lock, flags);
 
+	dev_vdbg(chan2dev(tx->chan), "tx_submit: queued %u\n",
+		 desc->txd.cookie);
 	return cookie;
 }
 
-- 
2.25.1