dmaengine: sh: rz-dmac: Protect the driver specific lists

The driver lists (ld_free, ld_queue) are used in
rz_dmac_free_chan_resources(), rz_dmac_terminate_all(),
rz_dmac_issue_pending(), and rz_dmac_irq_handler_thread(), all under
the virtual channel lock. Take the same lock in rz_dmac_prep_slave_sg()
and rz_dmac_prep_dma_memcpy() as well to avoid concurrency issues, since
these functions also check whether the lists are empty and update or
remove list entries.

Fixes: 5000d37 ("dmaengine: sh: Add DMAC driver for RZ/G2L SoC")
Cc: [email protected]
Reviewed-by: Frank Li <[email protected]>
Signed-off-by: Claudiu Beznea <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: claudiubeznea

drivers/dma/sh/rz-dmac.c

@@ -10,6 +10,7 @@
  */
 
 #include <linux/bitfield.h>
+#include <linux/cleanup.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/interrupt.h>
@@ -447,6 +448,7 @@ static int rz_dmac_alloc_chan_resources(struct dma_chan *chan)
 		if (!desc)
 			break;
 
+		/* No need to lock. This is called only for the 1st client. */
 		list_add_tail(&desc->node, &channel->ld_free);
 		channel->descs_allocated++;
 	}
@@ -502,18 +504,21 @@ rz_dmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 	dev_dbg(dmac->dev, "%s channel: %d src=0x%pad dst=0x%pad len=%zu\n",
 		__func__, channel->index, &src, &dest, len);
 
-	if (list_empty(&channel->ld_free))
-		return NULL;
+	scoped_guard(spinlock_irqsave, &channel->vc.lock) {
+		if (list_empty(&channel->ld_free))
+			return NULL;
+
+		desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
 
-	desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
+		desc->type = RZ_DMAC_DESC_MEMCPY;
+		desc->src = src;
+		desc->dest = dest;
+		desc->len = len;
+		desc->direction = DMA_MEM_TO_MEM;
 
-	desc->type = RZ_DMAC_DESC_MEMCPY;
-	desc->src = src;
-	desc->dest = dest;
-	desc->len = len;
-	desc->direction = DMA_MEM_TO_MEM;
+		list_move_tail(channel->ld_free.next, &channel->ld_queue);
+	}
 
-	list_move_tail(channel->ld_free.next, &channel->ld_queue);
 	return vchan_tx_prep(&channel->vc, &desc->vd, flags);
 }
 
@@ -529,27 +534,29 @@ rz_dmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	int dma_length = 0;
 	int i = 0;
 
-	if (list_empty(&channel->ld_free))
-		return NULL;
+	scoped_guard(spinlock_irqsave, &channel->vc.lock) {
+		if (list_empty(&channel->ld_free))
+			return NULL;
 
-	desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
+		desc = list_first_entry(&channel->ld_free, struct rz_dmac_desc, node);
 
-	for_each_sg(sgl, sg, sg_len, i) {
-		dma_length += sg_dma_len(sg);
-	}
+		for_each_sg(sgl, sg, sg_len, i)
+			dma_length += sg_dma_len(sg);
 
-	desc->type = RZ_DMAC_DESC_SLAVE_SG;
-	desc->sg = sgl;
-	desc->sgcount = sg_len;
-	desc->len = dma_length;
-	desc->direction = direction;
+		desc->type = RZ_DMAC_DESC_SLAVE_SG;
+		desc->sg = sgl;
+		desc->sgcount = sg_len;
+		desc->len = dma_length;
+		desc->direction = direction;
 
-	if (direction == DMA_DEV_TO_MEM)
-		desc->src = channel->src_per_address;
-	else
-		desc->dest = channel->dst_per_address;
+		if (direction == DMA_DEV_TO_MEM)
+			desc->src = channel->src_per_address;
+		else
+			desc->dest = channel->dst_per_address;
+
+		list_move_tail(channel->ld_free.next, &channel->ld_queue);
+	}
 
-	list_move_tail(channel->ld_free.next, &channel->ld_queue);
 	return vchan_tx_prep(&channel->vc, &desc->vd, flags);
 }