linux-kernel - [PATCH 4.2.y-ckt 85/98] dmaengine: pxa

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Message-Id: <1458084692-23100-86-git-send-email-kamal@canonical.com>
Date:	Tue, 15 Mar 2016 16:31:19 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Robert Jarzmik <robert.jarzmik@...e.fr>,
	Vinod Koul <vinod.koul@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 85/98] dmaengine: pxa_dma: fix cyclic transfers

4.2.8-ckt6 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Robert Jarzmik <robert.jarzmik@...e.fr>

commit f16921275cc3c2442d0b95225785a601603b990f upstream.

While testing audio with pxa2xx-ac97, underrun were happening while the
user application was correctly feeding the music. Debug proved that the
cyclic transfer is not cyclic, ie. the last descriptor did not loop on
the first.

Another issue is that the descriptor length was always set to 8192,
because of an trivial operator issue.

This was tested on a pxa27x platform.

Fixes: a57e16cf0333 ("dmaengine: pxa: add pxa dmaengine driver")
Reported-by: Vasily Khoruzhick <anarsoul@...il.com>
Tested-by: Vasily Khoruzhick <anarsoul@...il.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@...e.fr>
Signed-off-by: Vinod Koul <vinod.koul@...el.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/dma/pxa_dma.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
index 95bdbbe..76c3b02 100644
--- a/drivers/dma/pxa_dma.c
+++ b/drivers/dma/pxa_dma.c
@@ -580,6 +580,8 @@ static void set_updater_desc(struct pxad_desc_sw *sw_desc,
 		(PXA_DCMD_LENGTH & sizeof(u32));
 	if (flags & DMA_PREP_INTERRUPT)
 		updater->dcmd |= PXA_DCMD_ENDIRQEN;
+	if (sw_desc->cyclic)
+		sw_desc->hw_desc[sw_desc->nb_desc - 2]->ddadr = sw_desc->first;
 }
 
 static bool is_desc_completed(struct virt_dma_desc *vd)
@@ -670,6 +672,10 @@ static irqreturn_t pxad_chan_handler(int irq, void *dev_id)
 		dev_dbg(&chan->vc.chan.dev->device,
 			"%s(): checking txd %p[%x]: completed=%d\n",
 			__func__, vd, vd->tx.cookie, is_desc_completed(vd));
+		if (to_pxad_sw_desc(vd)->cyclic) {
+			vchan_cyclic_callback(vd);
+			break;
+		}
 		if (is_desc_completed(vd)) {
 			list_del(&vd->node);
 			vchan_cookie_complete(vd);
@@ -1073,7 +1079,7 @@ pxad_prep_dma_cyclic(struct dma_chan *dchan,
 		return NULL;
 
 	pxad_get_config(chan, dir, &dcmd, &dsadr, &dtadr);
-	dcmd |= PXA_DCMD_ENDIRQEN | (PXA_DCMD_LENGTH | period_len);
+	dcmd |= PXA_DCMD_ENDIRQEN | (PXA_DCMD_LENGTH & period_len);
 	dev_dbg(&chan->vc.chan.dev->device,
 		"%s(): buf_addr=0x%lx len=%zu period=%zu dir=%d flags=%lx\n",
 		__func__, (unsigned long)buf_addr, len, period_len, dir, flags);
-- 
2.7.0