[PATCH v3 01/15] dmaengine: dw: fix master selection

[Andy Shevchenko]

The commit 895005202987 ("dmaengine: dw: apply both HS interfaces and remove
slave_id usage") cleaned up the code to avoid usage of depricated slave_id
member of generic slave configuration.

Meanwhile it broke the master selection by removing important call to
dwc_set_masters() in ->device_alloc_chan_resources() which copied masters from
custom slave configuration to the internal channel structure.

Everything works until now since there is no customized connection of
DesignWare DMA IP to the bus, i.e. one bus and one or more masters are in use.
The configurations where 2 masters are connected to the different masters are
not working anymore. We are expecting one user of such configuration and need
to select masters properly. Besides that it is obviously a performance
regression since only one master is in use in multi-master configuration.

Select masters in accordance to what user asked for. Keep this patch in a form
more suitable for back porting.

We are safe to take necessary data in ->device_alloc_chan_resources() because
we don't support generic slave configuration embedded into custom one, and thus
the only way to provide it is to use parameter to a filter function which is
called exactly before channel resource allocation.

Fixes: 895005202987 ("dmaengine: dw: apply both HS interfaces and remove slave_id usage")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 drivers/dma/dw/core.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 5ad0ec1..ba46628 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -130,26 +130,14 @@ static void dwc_desc_put(struct dw_dma_chan *dwc, struct dw_desc *desc)
 static void dwc_initialize(struct dw_dma_chan *dwc)
 {
 	struct dw_dma *dw = to_dw_dma(dwc->chan.device);
-	struct dw_dma_slave *dws = dwc->chan.private;
 	u32 cfghi = DWC_CFGH_FIFO_MODE;
 	u32 cfglo = DWC_CFGL_CH_PRIOR(dwc->priority);
 
 	if (dwc->initialized == true)
 		return;
 
-	if (dws) {
-		/*
-		 * We need controller-specific data to set up slave
-		 * transfers.
-		 */
-		BUG_ON(!dws->dma_dev || dws->dma_dev != dw->dma.dev);
-
-		cfghi |= DWC_CFGH_DST_PER(dws->dst_id);
-		cfghi |= DWC_CFGH_SRC_PER(dws->src_id);
-	} else {
-		cfghi |= DWC_CFGH_DST_PER(dwc->dst_id);
-		cfghi |= DWC_CFGH_SRC_PER(dwc->src_id);
-	}
+	cfghi |= DWC_CFGH_DST_PER(dwc->dst_id);
+	cfghi |= DWC_CFGH_SRC_PER(dwc->src_id);
 
 	channel_writel(dwc, CFG_LO, cfglo);
 	channel_writel(dwc, CFG_HI, cfghi);
@@ -941,7 +929,7 @@ bool dw_dma_filter(struct dma_chan *chan, void *param)
 	struct dw_dma_chan *dwc = to_dw_dma_chan(chan);
 	struct dw_dma_slave *dws = param;
 
-	if (!dws || dws->dma_dev != chan->device->dev)
+	if (dws->dma_dev != chan->device->dev)
 		return false;
 
 	/* We have to copy data since dws can be temporary storage */
@@ -1165,6 +1153,11 @@ static int dwc_alloc_chan_resources(struct dma_chan *chan)
 	 * doesn't mean what you think it means), and status writeback.
 	 */
 
+	/*
+	 * We need controller-specific data to set up slave transfers.
+	 */
+	BUG_ON(chan->private && !dw_dma_filter(chan, chan->private));
+
 	/* Enable controller here if needed */
 	if (!dw->in_use)
 		dw_dma_on(dw);
@@ -1226,6 +1219,14 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
 	spin_lock_irqsave(&dwc->lock, flags);
 	list_splice_init(&dwc->free_list, &list);
 	dwc->descs_allocated = 0;
+
+	/* Clear custom channel configuration */
+	dwc->src_id = 0;
+	dwc->dst_id = 0;
+
+	dwc->src_master = 0;
+	dwc->dst_master = 0;
+
 	dwc->initialized = false;
 
 	/* Disable interrupts */
-- 
2.7.0