linux-kernel - [PATCH 4.0 047/105] dmaengine: Fix choppy sound because of unimplemented resume

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Date:	Fri, 19 Jun 2015 13:35:37 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	gabriel@...een.is, Marek Szyprowski <m.szyprowski@...sung.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Vinod Koul <vinod.koul@...el.com>
Subject: [PATCH 4.0 047/105] dmaengine: Fix choppy sound because of unimplemented resume

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Krzysztof Kozlowski <k.kozlowski@...sung.com>

commit 88d04643c66052a1cf92a6fd5f92dff0f7757f61 upstream.

Some drivers implement only pause operation (no resuming). Example is
pl330 where pause is needed for getting residuum. pl330 does not support
resume operation, transfer must be stopped after pause.

However for slaves this is exposed always as "pause and resume" which
introduces subtle errors on Odroid U3 board (Exynos4412 with pl330).
After adding pause function to pl330 driver the audio playback
(utilizing DMA) gets choppy after some time (approximately 24 hours).

Fix this by exposing "cmd_pause" if and only if pause and resume are
implemented.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
Reported-by: gabriel@...een.is
Reported-by: Marek Szyprowski <m.szyprowski@...sung.com>
Fixes: 88987d2c7534 ("dmaengine: pl330: add DMA_PAUSE feature")
Acked-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/dma/dmaengine.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -505,7 +505,11 @@ int dma_get_slave_caps(struct dma_chan *
 	caps->directions = device->directions;
 	caps->residue_granularity = device->residue_granularity;
 
-	caps->cmd_pause = !!device->device_pause;
+	/*
+	 * Some devices implement only pause (e.g. to get residuum) but no
+	 * resume. However cmd_pause is advertised as pause AND resume.
+	 */
+	caps->cmd_pause = !!(device->device_pause && device->device_resume);
 	caps->cmd_terminate = !!device->device_terminate_all;
 
 	return 0;


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