mmc: rtsx_pci: Remove deprecated create_singlethread_workqueue

The workqueue "workq" provides support for sd/mmc async request, which
makes next request do dma_map_sg() while previous request transferring
data.

The workqueue has a single workitem(&host->work) and hence doesn't require
ordering. Also, it is not being used on a memory reclaim path. Hence,
the singlethreaded workqueue has been replaced with the use of system_wq.

System workqueues have been able to handle high level of concurrency
for a long time now and hence it's not required to have a singlethreaded
workqueue just to gain concurrency. Unlike a dedicated per-cpu workqueue
created with create_singlethread_workqueue(), system_wq allows multiple
work items to overlap executions even on the same CPU; however, a
per-cpu workqueue doesn't have any CPU locality or global ordering
guarantee unless the target CPU is explicitly specified and thus the
increase of local concurrency shouldn't make any difference.

Work item has been flushed in rtsx_pci_sdmmc_drv_remove() to ensure that
there are no pending tasks while disconnecting the driver.
Signed-off-by: Bhaktipriya Shridhar <bhaktipriya96@gmail.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/rtsx_pci_sdmmc.c

@@ -38,7 +38,6 @@ struct realtek_pci_sdmmc {
 	struct rtsx_pcr		*pcr;
 	struct mmc_host		*mmc;
 	struct mmc_request	*mrq;
-	struct workqueue_struct *workq;
 #define SDMMC_WORKQ_NAME	"rtsx_pci_sdmmc_workq"
 
 	struct work_struct	work;
@@ -885,7 +884,7 @@ static void sdmmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	if (sd_rw_cmd(mrq->cmd) || sdio_extblock_cmd(mrq->cmd, data))
 		host->using_cookie = sd_pre_dma_transfer(host, data, false);
 
-	queue_work(host->workq, &host->work);
+	schedule_work(&host->work);
 }
 
 static int sd_set_bus_width(struct realtek_pci_sdmmc *host,
@@ -1404,11 +1403,6 @@ static int rtsx_pci_sdmmc_drv_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	host = mmc_priv(mmc);
-	host->workq = create_singlethread_workqueue(SDMMC_WORKQ_NAME);
-	if (!host->workq) {
-		mmc_free_host(mmc);
-		return -ENOMEM;
-	}
 	host->pcr = pcr;
 	host->mmc = mmc;
 	host->pdev = pdev;
@@ -1462,9 +1456,7 @@ static int rtsx_pci_sdmmc_drv_remove(struct platform_device *pdev)
 	mmc_remove_host(mmc);
 	host->eject = true;
 
-	flush_workqueue(host->workq);
-	destroy_workqueue(host->workq);
-	host->workq = NULL;
+	flush_work(&host->work);
 
 	mmc_free_host(mmc);