linux-kernel - [PATCH v2 6/7] dmaengine: dw: return immediately from IRQ when DMA isn't in use

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Message-Id: <1448551153-84719-7-git-send-email-andriy.shevchenko@linux.intel.com>
Date:	Thu, 26 Nov 2015 17:19:12 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-acpi@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
	dmaengine@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v2 6/7] dmaengine: dw: return immediately from IRQ when DMA isn't in use

There is no need to bother the hardware when all channels are idle. We have not
to get any interrupts.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
 drivers/dma/dw/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 7067b6d..8b20930 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -622,12 +622,17 @@ static void dw_dma_tasklet(unsigned long data)
 static irqreturn_t dw_dma_interrupt(int irq, void *dev_id)
 {
 	struct dw_dma *dw = dev_id;
-	u32 status = dma_readl(dw, STATUS_INT);
+	u32 status;
 
+	/* Check if we have any interrupt from the DMAC which is not in use */
+	if (!dw->in_use)
+		return IRQ_NONE;
+
+	status = dma_readl(dw, STATUS_INT);
 	dev_vdbg(dw->dma.dev, "%s: status=0x%x\n", __func__, status);
 
 	/* Check if we have any interrupt from the DMAC */
-	if (!status || !dw->in_use)
+	if (!status)
 		return IRQ_NONE;
 
 	/*
-- 
2.6.2

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