ASoC: fsi: don't reschedule DMA from an atomic context

shdma doesn't support transfer re-scheduling or triggering from callbacks
or from atomic context. The fsi driver issues DMA transfers from a tasklet
context, which is a bug. To fix it convert tasklet to a work.
Reported-by: Do Q.Thang <dq-thang@jinso.co.jp>
Tested-by: Do Q.Thang <dq-thang@jinso.co.jp>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: stable@vger.kernel.org

sound/soc/sh/fsi.c

@@ -20,6 +20,7 @@
 #include <linux/sh_dma.h>
 #include <linux/slab.h>
 #include <linux/module.h>
+#include <linux/workqueue.h>
 #include <sound/soc.h>
 #include <sound/sh_fsi.h>
 
@@ -223,7 +224,7 @@ struct fsi_stream {
 	 */
 	struct dma_chan		*chan;
 	struct sh_dmae_slave	slave; /* see fsi_handler_init() */
-	struct tasklet_struct	tasklet;
+	struct work_struct	work;
 	dma_addr_t		dma;
 };
 
@@ -1085,9 +1086,9 @@ static void fsi_dma_complete(void *data)
 	snd_pcm_period_elapsed(io->substream);
 }
 
-static void fsi_dma_do_tasklet(unsigned long data)
+static void fsi_dma_do_work(struct work_struct *work)
 {
-	struct fsi_stream *io = (struct fsi_stream *)data;
+	struct fsi_stream *io = container_of(work, struct fsi_stream, work);
 	struct fsi_priv *fsi = fsi_stream_to_priv(io);
 	struct snd_soc_dai *dai;
 	struct dma_async_tx_descriptor *desc;
@@ -1129,7 +1130,7 @@ static void fsi_dma_do_tasklet(unsigned long data)
 	 * FIXME
 	 *
 	 * In DMAEngine case, codec and FSI cannot be started simultaneously
-	 * since FSI is using tasklet.
+	 * since FSI is using the scheduler work queue.
 	 * Therefore, in capture case, probably FSI FIFO will have got
 	 * overflow error in this point.
 	 * in that case, DMA cannot start transfer until error was cleared.
@@ -1153,7 +1154,7 @@ static bool fsi_dma_filter(struct dma_chan *chan, void *param)
 
 static int fsi_dma_transfer(struct fsi_priv *fsi, struct fsi_stream *io)
 {
-	tasklet_schedule(&io->tasklet);
+	schedule_work(&io->work);
 
 	return 0;
 }
@@ -1195,14 +1196,14 @@ static int fsi_dma_probe(struct fsi_priv *fsi, struct fsi_stream *io, struct dev
 		return fsi_stream_probe(fsi, dev);
 	}
 
-	tasklet_init(&io->tasklet, fsi_dma_do_tasklet, (unsigned long)io);
+	INIT_WORK(&io->work, fsi_dma_do_work);
 
 	return 0;
 }
 
 static int fsi_dma_remove(struct fsi_priv *fsi, struct fsi_stream *io)
 {
-	tasklet_kill(&io->tasklet);
+	cancel_work_sync(&io->work);
 
 	fsi_stream_stop(fsi, io);