[PATCH v4 32/33] dmaengine: qcom-gpi: defer callbacks via vchan

[Allen Pais]

Complete descriptors through virt-dma instead of invoking callbacks
directly from event processing. This preserves the transfer result for
the shared vchan BH, which invokes the callback and frees the
descriptor.

Because callbacks are now deferred, synchronize the vchan before the
channel ring is freed in gpi_free_chan_resources(), so a late callback
cannot observe a torn-down ring, and provide a device_synchronize()
callback so dmaengine_terminate_sync() waits for pending callbacks.

Signed-off-by: Allen Pais <allen.lkml@xxxxxxxxx>
---
 drivers/dma/qcom/gpi.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
index d3c3d0f35afb..e125b3a83b1a 100644
--- a/drivers/dma/qcom/gpi.c
+++ b/drivers/dma/qcom/gpi.c
@@ -981,8 +981,12 @@ static void gpi_process_imed_data_event(struct gchan *gchan,
 		result.result = DMA_TRANS_NOERROR;
 	result.residue = gpi_desc->len - imed_event->length;
 
-	dma_cookie_complete(&vd->tx);
-	dmaengine_desc_get_callback_invoke(&vd->tx, &result);
+	spin_lock_irqsave(&gchan->vc.lock, flags);
+	list_del(&vd->node);
+	vd->tx_result = result;
+	vchan_cookie_complete(vd);
+	spin_unlock_irqrestore(&gchan->vc.lock, flags);
+	return;
 
 gpi_free_desc:
 	spin_lock_irqsave(&gchan->vc.lock, flags);
@@ -1060,8 +1064,12 @@ static void gpi_process_xfer_compl_event(struct gchan *gchan,
 	result.residue = gpi_desc->len - compl_event->length;
 	dev_dbg(gpii->gpi_dev->dev, "Residue %d\n", result.residue);
 
-	dma_cookie_complete(&vd->tx);
-	dmaengine_desc_get_callback_invoke(&vd->tx, &result);
+	spin_lock_irqsave(&gchan->vc.lock, flags);
+	list_del(&vd->node);
+	vd->tx_result = result;
+	vchan_cookie_complete(vd);
+	spin_unlock_irqrestore(&gchan->vc.lock, flags);
+	return;
 
 gpi_free_desc:
 	spin_lock_irqsave(&gchan->vc.lock, flags);
@@ -1983,6 +1991,13 @@ static int gpi_ch_init(struct gchan *gchan)
 }
 
 /* release all channel resources */
+static void gpi_synchronize(struct dma_chan *chan)
+{
+	struct gchan *gchan = to_gchan(chan);
+
+	vchan_synchronize(&gchan->vc);
+}
+
 static void gpi_free_chan_resources(struct dma_chan *chan)
 {
 	struct gchan *gchan = to_gchan(chan);
@@ -2010,6 +2025,9 @@ static void gpi_free_chan_resources(struct dma_chan *chan)
 		gpi_reset_chan(gchan, GPI_CH_CMD_DE_ALLOC);
 	}
 
+	/* drain deferred completions before the ring goes away */
+	vchan_synchronize(&gchan->vc);
+
 	/* free all allocated memory */
 	gpi_free_ring(&gchan->ch_ring, gpii);
 	vchan_free_chan_resources(&gchan->vc);
@@ -2279,6 +2297,7 @@ static int gpi_probe(struct platform_device *pdev)
 	gpi_dev->dma_device.device_prep_slave_sg = gpi_prep_slave_sg;
 	gpi_dev->dma_device.device_config = gpi_peripheral_config;
 	gpi_dev->dma_device.device_terminate_all = gpi_terminate_all;
+	gpi_dev->dma_device.device_synchronize = gpi_synchronize;
 	gpi_dev->dma_device.dev = gpi_dev->dev;
 	gpi_dev->dma_device.device_pause = gpi_pause;
 	gpi_dev->dma_device.device_resume = gpi_resume;
-- 
2.43.0