Patch "dmaengine: pxa_dma: fix cyclic transfers" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

dmaengine: pxa_dma: fix cyclic transfers

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dmaengine-pxa_dma-fix-cyclic-transfers.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Robert Jarzmik <[email protected]>
Date: Tue, 16 Feb 2016 22:54:02 +0100
Subject: dmaengine: pxa_dma: fix cyclic transfers

From: Robert Jarzmik <[email protected]>

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.

---
 drivers/dma/pxa_dma.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

@@ -583,6 +583,8 @@ static void set_updater_desc(struct pxad
 		(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)

@@ -673,6 +675,10 @@ static irqreturn_t pxad_chan_handler(int
 		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);

@@ -1080,7 +1086,7 @@ pxad_prep_dma_cyclic(struct dma_chan *dc
 		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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/dmaengine-pxa_dma-fix-cyclic-transfers.patch