mmc: msm_sdcc: Fix possible circular locking dependency warning

In the context of request processing thread, data mover lock is
acquired after the host lock.  In another context, in the completion
handler of data mover the locks are acquired in the reverse order,
resulting in possible circular lock dependency warning. Hence,
schedule a tasklet to process the dma completion so as to avoid
nested locks.

Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>

2 files changed, 36 insertions, 16 deletions

diff --git a/drivers/mmc/host/msm_sdcc.c b/drivers/mmc/host/msm_sdcc.c
index 1290d14c583..b147971a96e 100644
--- a/drivers/mmc/host/msm_sdcc.c
+++ b/drivers/mmc/host/msm_sdcc.c
@@ -189,42 +189,40 @@ msmsdcc_dma_exec_func(struct msm_dmov_cmd *cmd)
 }
 
 static void
-msmsdcc_dma_complete_func(struct msm_dmov_cmd *cmd,
-                          unsigned int result,
-                          struct msm_dmov_errdata *err)
+msmsdcc_dma_complete_tlet(unsigned long data)
 {
-        struct msmsdcc_dma_data *dma_data =
-                container_of(cmd, struct msmsdcc_dma_data, hdr);
-        struct msmsdcc_host     *host = dma_data->host;
+        struct msmsdcc_host *host = (struct msmsdcc_host *)data;
         unsigned long           flags;
         struct mmc_request      *mrq;
+        struct msm_dmov_errdata err;
 
         spin_lock_irqsave(&host->lock, flags);
         host->dma.active = 0;
 
+        err = host->dma.err;
         mrq = host->curr.mrq;
         BUG_ON(!mrq);
         WARN_ON(!mrq->data);
 
-        if (!(result & DMOV_RSLT_VALID)) {
+        if (!(host->dma.result & DMOV_RSLT_VALID)) {
                 pr_err("msmsdcc: Invalid DataMover result\n");
                 goto out;
         }
 
-        if (result & DMOV_RSLT_DONE) {
+        if (host->dma.result & DMOV_RSLT_DONE) {
                 host->curr.data_xfered = host->curr.xfer_size;
         } else {
                 /* Error or flush  */
-                if (result & DMOV_RSLT_ERROR)
+                if (host->dma.result & DMOV_RSLT_ERROR)
                         pr_err("%s: DMA error (0x%.8x)\n",
-                               mmc_hostname(host->mmc), result);
-                if (result & DMOV_RSLT_FLUSH)
+                               mmc_hostname(host->mmc), host->dma.result);
+                if (host->dma.result & DMOV_RSLT_FLUSH)
                         pr_err("%s: DMA channel flushed (0x%.8x)\n",
-                               mmc_hostname(host->mmc), result);
-                if (err)
-                        pr_err("Flush data: %.8x %.8x %.8x %.8x %.8x %.8x\n",
-                               err->flush[0], err->flush[1], err->flush[2],
-                               err->flush[3], err->flush[4], err->flush[5]);
+                               mmc_hostname(host->mmc), host->dma.result);
+
+                pr_err("Flush data: %.8x %.8x %.8x %.8x %.8x %.8x\n",
+                       err.flush[0], err.flush[1], err.flush[2],
+                       err.flush[3], err.flush[4], err.flush[5]);
                 if (!mrq->data->error)
                         mrq->data->error = -EIO;
         }
@@ -273,6 +271,22 @@ out:
         return;
 }
 
+static void
+msmsdcc_dma_complete_func(struct msm_dmov_cmd *cmd,
+                          unsigned int result,
+                          struct msm_dmov_errdata *err)
+{
+        struct msmsdcc_dma_data *dma_data =
+                container_of(cmd, struct msmsdcc_dma_data, hdr);
+        struct msmsdcc_host *host = dma_data->host;
+
+        dma_data->result = result;
+        if (err)
+                memcpy(&dma_data->err, err, sizeof(struct msm_dmov_errdata));
+
+        tasklet_schedule(&host->dma_tlet);
+}
+
 static int validate_dma(struct msmsdcc_host *host, struct mmc_data *data)
 {
         if (host->dma.channel == -1)
@@ -1118,6 +1132,9 @@ msmsdcc_probe(struct platform_device *pdev)
         host->dmares = dmares;
         spin_lock_init(&host->lock);
 
+        tasklet_init(&host->dma_tlet, msmsdcc_dma_complete_tlet,
+                        (unsigned long)host);
+
         /*
          * Setup DMA
          */
diff --git a/drivers/mmc/host/msm_sdcc.h b/drivers/mmc/host/msm_sdcc.h
index ff2b0f74f6f..996990dfc7c 100644
--- a/drivers/mmc/host/msm_sdcc.h
+++ b/drivers/mmc/host/msm_sdcc.h
@@ -172,6 +172,8 @@ struct msmsdcc_dma_data {
         struct msmsdcc_host             *host;
         int                             busy; /* Set if DM is busy */
         int                             active;
+        unsigned int                    result;
+        struct msm_dmov_errdata         err;
 };
 
 struct msmsdcc_pio_data {
@@ -235,6 +237,7 @@ struct msmsdcc_host {
         int                     cmdpoll;
         struct msmsdcc_stats    stats;
 
+        struct tasklet_struct   dma_tlet;
         /* Command parameters */
         unsigned int            cmd_timeout;
         unsigned int            cmd_pio_irqmask;