dmaengine: bcm-sba-raid: Use only single mailbox channel

Each mailbox channel used by Broadcom SBA RAID driver is
a separate HW ring.

Currently, Broadcom SBA RAID driver creates one DMA channel
using one or more mailbox channels. When we are using more
than one mailbox channels for a DMA channel, the sba_request
are distributed evenly among multiple mailbox channels which
results in sba_request being completed out-of-order.

The above described out-of-order completion of sba_request
breaks the dma_async_is_complete() API because it assumes
DMA cookies are completed in orderly fashion.

To ensure correct behaviour of dma_async_is_complete() API,
this patch updates Broadcom SBA RAID driver to use only
single mailbox channel. If additional mailbox channels are
specified in DT then those will be ignored.

Signed-off-by: Anup Patel <anup.patel@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Reviewed-by: Scott Branden <scott.branden@broadcom.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 27 insertions, 77 deletions

diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
index 15c558508345..409da59d9315 100644
--- a/drivers/dma/bcm-sba-raid.c
+++ b/drivers/dma/bcm-sba-raid.c
@@ -25,11 +25,8 @@
  *
  * The Broadcom SBA RAID driver does not require any register programming
  * except submitting request to SBA hardware device via mailbox channels.
- * This driver implements a DMA device with one DMA channel using a set
- * of mailbox channels provided by Broadcom SoC specific ring manager
- * driver. To exploit parallelism (as described above), all DMA request
- * coming to SBA RAID DMA channel are broken down to smaller requests
- * and submitted to multiple mailbox channels in round-robin fashion.
+ * This driver implements a DMA device with one DMA channel using a single
+ * mailbox channel provided by Broadcom SoC specific ring manager driver.
  * For having more SBA DMA channels, we can create more SBA device nodes
  * in Broadcom SoC specific DTS based on number of hardware rings supported
  * by Broadcom SoC ring manager.
@@ -85,6 +82,7 @@
 #define SBA_CMD_GALOIS                                  0xe
 
 #define SBA_MAX_REQ_PER_MBOX_CHANNEL                    8192
+#define SBA_MAX_MSG_SEND_PER_MBOX_CHANNEL               8
 
 /* Driver helper macros */
 #define to_sba_request(tx)              \
@@ -142,9 +140,7 @@ struct sba_device {
         u32 max_cmds_pool_size;
         /* Maibox client and Mailbox channels */
         struct mbox_client client;
-        int mchans_count;
-        atomic_t mchans_current;
-        struct mbox_chan **mchans;
+        struct mbox_chan *mchan;
         struct device *mbox_dev;
         /* DMA device and DMA channel */
         struct dma_device dma_dev;
@@ -200,14 +196,6 @@ static inline u32 __pure sba_cmd_pq_c_mdata(u32 d, u32 b1, u32 b0)
 
 /* ====== General helper routines ===== */
 
-static void sba_peek_mchans(struct sba_device *sba)
-{
-        int mchan_idx;
-
-        for (mchan_idx = 0; mchan_idx < sba->mchans_count; mchan_idx++)
-                mbox_client_peek_data(sba->mchans[mchan_idx]);
-}
-
 static struct sba_request *sba_alloc_request(struct sba_device *sba)
 {
         bool found = false;
@@ -231,7 +219,7 @@ static struct sba_request *sba_alloc_request(struct sba_device *sba)
                  * would have completed which will create more
                  * room for new requests.
                  */
-                sba_peek_mchans(sba);
+                mbox_client_peek_data(sba->mchan);
                 return NULL;
         }
 
@@ -369,15 +357,11 @@ static void sba_cleanup_pending_requests(struct sba_device *sba)
 static int sba_send_mbox_request(struct sba_device *sba,
                                  struct sba_request *req)
 {
-        int mchans_idx, ret = 0;
-
-        /* Select mailbox channel in round-robin fashion */
-        mchans_idx = atomic_inc_return(&sba->mchans_current);
-        mchans_idx = mchans_idx % sba->mchans_count;
+        int ret = 0;
 
         /* Send message for the request */
         req->msg.error = 0;
-        ret = mbox_send_message(sba->mchans[mchans_idx], &req->msg);
+        ret = mbox_send_message(sba->mchan, &req->msg);
         if (ret < 0) {
                 dev_err(sba->dev, "send message failed with error %d", ret);
                 return ret;
@@ -390,7 +374,7 @@ static int sba_send_mbox_request(struct sba_device *sba,
         }
 
         /* Signal txdone for mailbox channel */
-        mbox_client_txdone(sba->mchans[mchans_idx], ret);
+        mbox_client_txdone(sba->mchan, ret);
 
         return ret;
 }
@@ -402,13 +386,8 @@ static void _sba_process_pending_requests(struct sba_device *sba)
         u32 count;
         struct sba_request *req;
 
-        /*
-         * Process few pending requests
-         *
-         * For now, we process (<number_of_mailbox_channels> * 8)
-         * number of requests at a time.
-         */
-        count = sba->mchans_count * 8;
+        /* Process few pending requests */
+        count = SBA_MAX_MSG_SEND_PER_MBOX_CHANNEL;
         while (!list_empty(&sba->reqs_pending_list) && count) {
                 /* Get the first pending request */
                 req = list_first_entry(&sba->reqs_pending_list,
@@ -572,7 +551,7 @@ static enum dma_status sba_tx_status(struct dma_chan *dchan,
         if (ret == DMA_COMPLETE)
                 return ret;
 
-        sba_peek_mchans(sba);
+        mbox_client_peek_data(sba->mchan);
 
         return dma_cookie_status(dchan, cookie, txstate);
 }
@@ -1639,7 +1618,7 @@ static int sba_async_register(struct sba_device *sba)
 
 static int sba_probe(struct platform_device *pdev)
 {
-        int i, ret = 0, mchans_count;
+        int ret = 0;
         struct sba_device *sba;
         struct platform_device *mbox_pdev;
         struct of_phandle_args args;
@@ -1652,12 +1631,11 @@ static int sba_probe(struct platform_device *pdev)
         sba->dev = &pdev->dev;
         platform_set_drvdata(pdev, sba);
 
-        /* Number of channels equals number of mailbox channels */
+        /* Number of mailbox channels should be atleast 1 */
         ret = of_count_phandle_with_args(pdev->dev.of_node,
                                          "mboxes", "#mbox-cells");
         if (ret <= 0)
                 return -ENODEV;
-        mchans_count = ret;
 
         /* Determine SBA version from DT compatible string */
         if (of_device_is_compatible(sba->dev->of_node, "brcm,iproc-sba"))
@@ -1690,7 +1668,7 @@ static int sba_probe(struct platform_device *pdev)
         default:
                 return -EINVAL;
         }
-        sba->max_req = SBA_MAX_REQ_PER_MBOX_CHANNEL * mchans_count;
+        sba->max_req = SBA_MAX_REQ_PER_MBOX_CHANNEL;
         sba->max_cmd_per_req = sba->max_pq_srcs + 3;
         sba->max_xor_srcs = sba->max_cmd_per_req - 1;
         sba->max_resp_pool_size = sba->max_req * sba->hw_resp_size;
@@ -1704,55 +1682,30 @@ static int sba_probe(struct platform_device *pdev)
         sba->client.knows_txdone        = true;
         sba->client.tx_tout             = 0;
 
-        /* Allocate mailbox channel array */
-        sba->mchans = devm_kcalloc(&pdev->dev, mchans_count,
-                                   sizeof(*sba->mchans), GFP_KERNEL);
-        if (!sba->mchans)
-                return -ENOMEM;
-
-        /* Request mailbox channels */
-        sba->mchans_count = 0;
-        for (i = 0; i < mchans_count; i++) {
-                sba->mchans[i] = mbox_request_channel(&sba->client, i);
-                if (IS_ERR(sba->mchans[i])) {
-                        ret = PTR_ERR(sba->mchans[i]);
-                        goto fail_free_mchans;
-                }
-                sba->mchans_count++;
+        /* Request mailbox channel */
+        sba->mchan = mbox_request_channel(&sba->client, 0);
+        if (IS_ERR(sba->mchan)) {
+                ret = PTR_ERR(sba->mchan);
+                goto fail_free_mchan;
         }
-        atomic_set(&sba->mchans_current, 0);
 
         /* Find-out underlying mailbox device */
         ret = of_parse_phandle_with_args(pdev->dev.of_node,
                                          "mboxes", "#mbox-cells", 0, &args);
         if (ret)
-                goto fail_free_mchans;
+                goto fail_free_mchan;
         mbox_pdev = of_find_device_by_node(args.np);
         of_node_put(args.np);
         if (!mbox_pdev) {
                 ret = -ENODEV;
-                goto fail_free_mchans;
+                goto fail_free_mchan;
         }
         sba->mbox_dev = &mbox_pdev->dev;
 
-        /* All mailbox channels should be of same ring manager device */
-        for (i = 1; i < mchans_count; i++) {
-                ret = of_parse_phandle_with_args(pdev->dev.of_node,
-                                         "mboxes", "#mbox-cells", i, &args);
-                if (ret)
-                        goto fail_free_mchans;
-                mbox_pdev = of_find_device_by_node(args.np);
-                of_node_put(args.np);
-                if (sba->mbox_dev != &mbox_pdev->dev) {
-                        ret = -EINVAL;
-                        goto fail_free_mchans;
-                }
-        }
-
         /* Prealloc channel resource */
         ret = sba_prealloc_channel_resources(sba);
         if (ret)
-                goto fail_free_mchans;
+                goto fail_free_mchan;
 
         /* Check availability of debugfs */
         if (!debugfs_initialized())
@@ -1779,24 +1732,22 @@ skip_debugfs:
                 goto fail_free_resources;
 
         /* Print device info */
-        dev_info(sba->dev, "%s using SBAv%d and %d mailbox channels",
+        dev_info(sba->dev, "%s using SBAv%d mailbox channel from %s",
                  dma_chan_name(&sba->dma_chan), sba->ver+1,
-                 sba->mchans_count);
+                 dev_name(sba->mbox_dev));
 
         return 0;
 
 fail_free_resources:
         debugfs_remove_recursive(sba->root);
         sba_freeup_channel_resources(sba);
-fail_free_mchans:
-        for (i = 0; i < sba->mchans_count; i++)
-                mbox_free_channel(sba->mchans[i]);
+fail_free_mchan:
+        mbox_free_channel(sba->mchan);
         return ret;
 }
 
 static int sba_remove(struct platform_device *pdev)
 {
-        int i;
         struct sba_device *sba = platform_get_drvdata(pdev);
 
         dma_async_device_unregister(&sba->dma_dev);
@@ -1805,8 +1756,7 @@ static int sba_remove(struct platform_device *pdev)
 
         sba_freeup_channel_resources(sba);
 
-        for (i = 0; i < sba->mchans_count; i++)
-                mbox_free_channel(sba->mchans[i]);
+        mbox_free_channel(sba->mchan);
 
         return 0;
 }