[PATCH v3 2/3] staging: mt7621-mmc: Initialize completions a single time during probe

[George Hilliard <thirtythreeforty@gmail.com>]

The module was initializing completions whenever it was going to wait on
them, and not when the completion was allocated.  This is incorrect
according to the completion docs:

    Calling init_completion() on the same completion object twice is
    most likely a bug [...]

Re-initialization is also unnecessary because the module never uses
complete_all().  Fix this by only ever initializing the completion a
single time, and log if the completions are not consumed as intended
(this is not a fatal problem, but should not go unnoticed).

Signed-off-by: George Hilliard <thirtythreeforty@gmail.com>
---
v2: Rebased v1
v3: Removed BUG_ON() calls, and politely log; this failure won't kill us

 drivers/staging/mt7621-mmc/sd.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/mt7621-mmc/sd.c b/drivers/staging/mt7621-mmc/sd.c
index ff01872ab972..139533606863 100644
--- a/drivers/staging/mt7621-mmc/sd.c
+++ b/drivers/staging/mt7621-mmc/sd.c
@@ -466,7 +466,10 @@ static unsigned int msdc_command_start(struct msdc_host   *host,
 	host->cmd     = cmd;
 	host->cmd_rsp = resp;
 
-	init_completion(&host->cmd_done);
+	// The completion should have been consumed by the previous command
+	// response handler, because the mmc requests should be serialized
+	if(completion_done(&host->cmd_done))
+		dev_err(mmc_dev(host->mmc), "previous command was not handled\n");
 
 	sdr_set_bits(host->base + MSDC_INTEN, wints);
 	sdc_send_cmd(rawcmd, cmd->arg);
@@ -488,7 +491,6 @@ static unsigned int msdc_command_resp(struct msdc_host   *host,
 		    MSDC_INT_ACMD19_DONE;
 
 	BUG_ON(in_interrupt());
-	//init_completion(&host->cmd_done);
 	//sdr_set_bits(host->base + MSDC_INTEN, wints);
 
 	spin_unlock(&host->lock);
@@ -672,7 +674,11 @@ static int msdc_do_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		//msdc_clr_fifo(host);  /* no need */
 
 		msdc_dma_on();  /* enable DMA mode first!! */
-		init_completion(&host->xfer_done);
+
+		// The completion should have been consumed by the previous xfer
+		// response handler, because the mmc requests should be serialized
+		if(completion_done(&host->cmd_done))
+			dev_err(mmc_dev(host->mmc), "previous transfer was not handled\n");
 
 		/* start the command first*/
 		if (msdc_command_start(host, cmd, CMD_TIMEOUT) != 0)
@@ -691,7 +697,6 @@ static int msdc_do_request(struct mmc_host *mmc, struct mmc_request *mrq)
 		/* for read, the data coming too fast, then CRC error
 		 *  start DMA no business with CRC.
 		 */
-		//init_completion(&host->xfer_done);
 		msdc_dma_start(host);
 
 		spin_unlock(&host->lock);
@@ -1682,6 +1687,8 @@ static int msdc_drv_probe(struct platform_device *pdev)
 	}
 	msdc_init_gpd_bd(host, &host->dma);
 
+	init_completion(&host->cmd_done);
+	init_completion(&host->xfer_done);
 	INIT_DELAYED_WORK(&host->card_delaywork, msdc_tasklet_card);
 	spin_lock_init(&host->lock);
 	msdc_init_hw(host);
-- 
2.21.0