spi: bcm2835: Synchronize with callback on DMA termination

Commit b36f09c3 ("dmaengine: Add transfer termination
synchronization support") deprecated dmaengine_terminate_all() in favor
of dmaengine_terminate_sync() and dmaengine_terminate_async() to avoid
freeing resources used by the DMA callback before its execution has
concluded.

Commit de92436a ("dmaengine: bcm2835-dma: Use vchan_terminate_vdesc()
instead of desc_free") amended the BCM2835 DMA driver with an
implementation of ->device_synchronize(), which is a prerequisite for
dmaengine_terminate_sync().  Thus, clients of the DMA driver (such as
the BCM2835 SPI driver) may now be converted to the new API.

It is generally desirable to use the _sync() variant except in atomic
context.  There is only a single occurrence where the BCM2835 SPI driver
calls dmaengine_terminate_all() in atomic context and that is in
bcm2835_spi_dma_done() (the RX DMA channel's callback) to terminate the
TX DMA channel.  The TX DMA channel doesn't have a callback (yet), hence
it is safe to use the _async() variant there.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm2835.c

@@ -514,7 +514,7 @@ static void bcm2835_spi_dma_done(void *data)
 	 * situation otherwise...
 	 */
 	if (cmpxchg(&bs->dma_pending, true, false)) {
-		dmaengine_terminate_all(master->dma_tx);
+		dmaengine_terminate_async(master->dma_tx);
 		bcm2835_spi_undo_prologue(bs);
 	}
 
@@ -605,7 +605,7 @@ static int bcm2835_spi_transfer_one_dma(struct spi_master *master,
 	ret = bcm2835_spi_prepare_sg(master, tfr, false);
 	if (ret) {
 		/* need to reset on errors */
-		dmaengine_terminate_all(master->dma_tx);
+		dmaengine_terminate_sync(master->dma_tx);
 		bs->dma_pending = false;
 		goto err_reset_hw;
 	}
@@ -650,12 +650,12 @@ static bool bcm2835_spi_can_dma(struct spi_master *master,
 static void bcm2835_dma_release(struct spi_master *master)
 {
 	if (master->dma_tx) {
-		dmaengine_terminate_all(master->dma_tx);
+		dmaengine_terminate_sync(master->dma_tx);
 		dma_release_channel(master->dma_tx);
 		master->dma_tx = NULL;
 	}
 	if (master->dma_rx) {
-		dmaengine_terminate_all(master->dma_rx);
+		dmaengine_terminate_sync(master->dma_rx);
 		dma_release_channel(master->dma_rx);
 		master->dma_rx = NULL;
 	}
@@ -864,8 +864,8 @@ static void bcm2835_spi_handle_err(struct spi_master *master,
 
 	/* if an error occurred and we have an active dma, then terminate */
 	if (cmpxchg(&bs->dma_pending, true, false)) {
-		dmaengine_terminate_all(master->dma_tx);
-		dmaengine_terminate_all(master->dma_rx);
+		dmaengine_terminate_sync(master->dma_tx);
+		dmaengine_terminate_sync(master->dma_rx);
 		bcm2835_spi_undo_prologue(bs);
 	}
 	/* and reset */