mmc: dw_mmc: make multiple instances of dw_mci_card_workqueue

The variable 'dw_mci_card_workqueue' is a global variable shared between
multiple instances of the dw_mmc host controller. Due to this, data
corruption has been noticed when multiple instances of dw_mmc controllers
are actively reading/writing the media. Fix this by adding a instance
of 'struct workqueue_struct' for each host instance and removing the
global 'dw_mci_card_workqueue' instance.

Signed-off-by: Thomas Abraham <[e-mail]>
Acked-by: Jaehoon Chung <[e-mail]>
Acked-by: Will Newton <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/dw_mmc.c

···
 	int			last_detect_state;
 };
 
-static struct workqueue_struct *dw_mci_card_workqueue;
-
 #if defined(CONFIG_DEBUG_FS)
 static int dw_mci_req_show(struct seq_file *s, void *v)
 {
···
 
 		if (pending & SDMMC_INT_CD) {
 			mci_writel(host, RINTSTS, SDMMC_INT_CD);
-			queue_work(dw_mci_card_workqueue, &host->card_work);
+			queue_work(host->card_workqueue, &host->card_work);
 		}
 
 		/* Handle SDIO Interrupts */
···
 	 * Card may have been plugged in prior to boot so we
 	 * need to run the detect tasklet
 	 */
-	queue_work(dw_mci_card_workqueue, &host->card_work);
+	queue_work(host->card_workqueue, &host->card_work);
 
 	return 0;
 }
···
 	mci_writel(host, CLKSRC, 0);
 
 	tasklet_init(&host->tasklet, dw_mci_tasklet_func, (unsigned long)host);
-	dw_mci_card_workqueue = alloc_workqueue("dw-mci-card",
+	host->card_workqueue = alloc_workqueue("dw-mci-card",
 			WQ_MEM_RECLAIM | WQ_NON_REENTRANT, 1);
-	if (!dw_mci_card_workqueue)
+	if (!host->card_workqueue)
 		goto err_dmaunmap;
 	INIT_WORK(&host->card_work, dw_mci_work_routine_card);
 	ret = request_irq(host->irq, dw_mci_interrupt, host->irq_flags, "dw-mci", host);
···
 	free_irq(host->irq, host);
 
 err_workqueue:
-	destroy_workqueue(dw_mci_card_workqueue);
+	destroy_workqueue(host->card_workqueue);
 
 err_dmaunmap:
 	if (host->use_dma && host->dma_ops->exit)
···
 	mci_writel(host, CLKSRC, 0);
 
 	free_irq(host->irq, host);
-	destroy_workqueue(dw_mci_card_workqueue);
+	destroy_workqueue(host->card_workqueue);
 	dma_free_coherent(&host->dev, PAGE_SIZE, host->sg_cpu, host->sg_dma);
 
 	if (host->use_dma && host->dma_ops->exit)

include/linux/mmc/dw_mmc.h

···
 	struct mmc_request	*mrq;
 	struct mmc_command	*cmd;
 	struct mmc_data		*data;
+	struct workqueue_struct	*card_workqueue;
 
 	/* DMA interface members*/
 	int			use_dma;