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Subject[PATCH 2/4] dmaengine: bcm-sba-raid: Use only single mailbox channel
Date
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>
---
drivers/dma/bcm-sba-raid.c | 104 ++++++++++++---------------------------------
1 file changed, 27 insertions(+), 77 deletions(-)

diff --git a/drivers/dma/bcm-sba-raid.c b/drivers/dma/bcm-sba-raid.c
index 15c5585..409da59 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 @@ static int sba_probe(struct platform_device *pdev)
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;
}
--
2.7.4
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