[PATCH 4.4 43/74] dmaengine: pxa_dma: fix cyclic transfers

Greg Kroah-Hartman
2016-03-08T00:13:54Z

From: Robert Jarzmik <robert.jarzmik@free.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@gmail.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/drivers/dma/pxa_dma.c
+++ b/drivers/dma/pxa_dma.c
@@ -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);