mmc: sdhi: Convert from tasklet to BH workqueue

The only generic interface to execute asynchronously in the BH context is
tasklet; however, it's marked deprecated and has some design flaws. To
replace tasklets, BH workqueue support was recently added. A BH workqueue
behaves similarly to regular workqueues except that the queued work items
are executed in the BH context.

This patch converts the SDHI driver from tasklet to BH workqueue.

Based on the work done by Tejun Heo <tj@kernel.org>
Signed-off-by: Allen Pais <allen.lkml@gmail.com>
[wsa: fixed build faliures, corrected whitespace issues]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20240626085015.32171-2-wsa+renesas@sang-engineering.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/renesas_sdhi.h

@@ -11,6 +11,7 @@
 
 #include <linux/dmaengine.h>
 #include <linux/platform_device.h>
+#include <linux/workqueue.h>
 #include "tmio_mmc.h"
 
 struct renesas_sdhi_scc {
@@ -67,7 +68,7 @@ struct renesas_sdhi_dma {
 	dma_filter_fn filter;
 	void (*enable)(struct tmio_mmc_host *host, bool enable);
 	struct completion dma_dataend;
-	struct tasklet_struct dma_complete;
+	struct work_struct dma_complete;
 };
 
 struct renesas_sdhi {
@@ -93,6 +94,7 @@ struct renesas_sdhi {
 	unsigned int tap_set;
 
 	struct reset_control *rstc;
+	struct tmio_mmc_host *host;
 };
 
 #define host_to_priv(host) \

drivers/mmc/host/renesas_sdhi_core.c

@@ -970,6 +970,8 @@ int renesas_sdhi_probe(struct platform_device *pdev,
 	if (IS_ERR(host))
 		return PTR_ERR(host);
 
+	priv->host = host;
+
 	if (of_data) {
 		mmc_data->flags |= of_data->tmio_flags;
 		mmc_data->ocr_mask = of_data->tmio_ocr_mask;

drivers/mmc/host/renesas_sdhi_internal_dmac.c

@@ -337,7 +337,7 @@ static bool renesas_sdhi_internal_dmac_dma_irq(struct tmio_mmc_host *host)
 		writel(status ^ dma_irqs, host->ctl + DM_CM_INFO1);
 		set_bit(SDHI_DMA_END_FLAG_DMA, &dma_priv->end_flags);
 		if (test_bit(SDHI_DMA_END_FLAG_ACCESS, &dma_priv->end_flags))
-			tasklet_schedule(&dma_priv->dma_complete);
+			queue_work(system_bh_wq, &dma_priv->dma_complete);
 	}
 
 	return status & dma_irqs;
@@ -352,7 +352,7 @@ renesas_sdhi_internal_dmac_dataend_dma(struct tmio_mmc_host *host)
 	set_bit(SDHI_DMA_END_FLAG_ACCESS, &dma_priv->end_flags);
 	if (test_bit(SDHI_DMA_END_FLAG_DMA, &dma_priv->end_flags) ||
 	    host->data->error)
-		tasklet_schedule(&dma_priv->dma_complete);
+		queue_work(system_bh_wq, &dma_priv->dma_complete);
 }
 
 /*
@@ -440,9 +440,9 @@ renesas_sdhi_internal_dmac_start_dma(struct tmio_mmc_host *host,
 	renesas_sdhi_internal_dmac_enable_dma(host, false);
 }
 
-static void renesas_sdhi_internal_dmac_issue_tasklet_fn(unsigned long arg)
+static void renesas_sdhi_internal_dmac_issue_work_fn(struct work_struct *work)
 {
-	struct tmio_mmc_host *host = (struct tmio_mmc_host *)arg;
+	struct tmio_mmc_host *host = from_work(host, work, dma_issue);
 	struct renesas_sdhi *priv = host_to_priv(host);
 
 	tmio_mmc_enable_mmc_irqs(host, TMIO_STAT_DATAEND);
@@ -454,7 +454,7 @@ static void renesas_sdhi_internal_dmac_issue_tasklet_fn(unsigned long arg)
 		/* on CMD errors, simulate DMA end immediately */
 		set_bit(SDHI_DMA_END_FLAG_DMA, &priv->dma_priv.end_flags);
 		if (test_bit(SDHI_DMA_END_FLAG_ACCESS, &priv->dma_priv.end_flags))
-			tasklet_schedule(&priv->dma_priv.dma_complete);
+			queue_work(system_bh_wq, &priv->dma_priv.dma_complete);
 	}
 }
 
@@ -484,9 +484,11 @@ static bool renesas_sdhi_internal_dmac_complete(struct tmio_mmc_host *host)
 	return true;
 }
 
-static void renesas_sdhi_internal_dmac_complete_tasklet_fn(unsigned long arg)
+static void renesas_sdhi_internal_dmac_complete_work_fn(struct work_struct *work)
 {
-	struct tmio_mmc_host *host = (struct tmio_mmc_host *)arg;
+	struct renesas_sdhi_dma *dma_priv = from_work(dma_priv, work, dma_complete);
+	struct renesas_sdhi *priv = container_of(dma_priv, typeof(*priv), dma_priv);
+	struct tmio_mmc_host *host = priv->host;
 
 	spin_lock_irq(&host->lock);
 	if (!renesas_sdhi_internal_dmac_complete(host))
@@ -544,12 +546,10 @@ renesas_sdhi_internal_dmac_request_dma(struct tmio_mmc_host *host,
 	/* Each value is set to non-zero to assume "enabling" each DMA */
 	host->chan_rx = host->chan_tx = (void *)0xdeadbeaf;
 
-	tasklet_init(&priv->dma_priv.dma_complete,
-		     renesas_sdhi_internal_dmac_complete_tasklet_fn,
-		     (unsigned long)host);
-	tasklet_init(&host->dma_issue,
-		     renesas_sdhi_internal_dmac_issue_tasklet_fn,
-		     (unsigned long)host);
+	INIT_WORK(&priv->dma_priv.dma_complete,
+		  renesas_sdhi_internal_dmac_complete_work_fn);
+	INIT_WORK(&host->dma_issue,
+		  renesas_sdhi_internal_dmac_issue_work_fn);
 
 	/* Add pre_req and post_req */
 	host->ops.pre_req = renesas_sdhi_internal_dmac_pre_req;

drivers/mmc/host/renesas_sdhi_sys_dmac.c

@@ -312,9 +312,9 @@ static void renesas_sdhi_sys_dmac_start_dma(struct tmio_mmc_host *host,
 	}
 }
 
-static void renesas_sdhi_sys_dmac_issue_tasklet_fn(unsigned long priv)
+static void renesas_sdhi_sys_dmac_issue_work_fn(struct work_struct *work)
 {
-	struct tmio_mmc_host *host = (struct tmio_mmc_host *)priv;
+	struct tmio_mmc_host *host = from_work(host, work, dma_issue);
 	struct dma_chan *chan = NULL;
 
 	spin_lock_irq(&host->lock);
@@ -401,9 +401,8 @@ static void renesas_sdhi_sys_dmac_request_dma(struct tmio_mmc_host *host,
 			goto ebouncebuf;
 
 		init_completion(&priv->dma_priv.dma_dataend);
-		tasklet_init(&host->dma_issue,
-			     renesas_sdhi_sys_dmac_issue_tasklet_fn,
-			     (unsigned long)host);
+		INIT_WORK(&host->dma_issue,
+			  renesas_sdhi_sys_dmac_issue_work_fn);
 	}
 
 	renesas_sdhi_sys_dmac_enable_dma(host, true);

drivers/mmc/host/tmio_mmc.h

@@ -21,6 +21,7 @@
 #include <linux/scatterlist.h>
 #include <linux/spinlock.h>
 #include <linux/interrupt.h>
+#include <linux/workqueue.h>
 
 #define CTL_SD_CMD 0x00
 #define CTL_ARG_REG 0x04
@@ -153,7 +154,7 @@ struct tmio_mmc_host {
 	bool			dma_on;
 	struct dma_chan		*chan_rx;
 	struct dma_chan		*chan_tx;
-	struct tasklet_struct	dma_issue;
+	struct work_struct	dma_issue;
 	struct scatterlist	bounce_sg;
 	u8			*bounce_buf;
 

drivers/mmc/host/tmio_mmc_core.c

@@ -608,7 +608,7 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host, unsigned int stat)
 			} else {
 				tmio_mmc_disable_mmc_irqs(host,
 							  TMIO_MASK_READOP);
-				tasklet_schedule(&host->dma_issue);
+				queue_work(system_bh_wq, &host->dma_issue);
 			}
 		} else {
 			if (!host->dma_on) {
@@ -616,7 +616,7 @@ static void tmio_mmc_cmd_irq(struct tmio_mmc_host *host, unsigned int stat)
 			} else {
 				tmio_mmc_disable_mmc_irqs(host,
 							  TMIO_MASK_WRITEOP);
-				tasklet_schedule(&host->dma_issue);
+				queue_work(system_bh_wq, &host->dma_issue);
 			}
 		}
 	} else {