mailbox: 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.

Based on the work done by Tejun Heo <tj@kernel.org>
Branch: https://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10
Signed-off-by: Allen Pais <allen.lkml@gmail.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>

drivers/mailbox/bcm-pdc-mailbox.c

@@ -43,6 +43,7 @@
 #include <linux/dma-direction.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmapool.h>
+#include <linux/workqueue.h>
 
 #define PDC_SUCCESS  0
 
@@ -293,8 +294,8 @@ struct pdc_state {
 
 	unsigned int pdc_irq;
 
-	/* tasklet for deferred processing after DMA rx interrupt */
-	struct tasklet_struct rx_tasklet;
+	/* work for deferred processing after DMA rx interrupt */
+	struct work_struct rx_work;
 
 	/* Number of bytes of receive status prior to each rx frame */
 	u32 rx_status_len;
@@ -952,18 +953,18 @@ static irqreturn_t pdc_irq_handler(int irq, void *data)
 	iowrite32(intstatus, pdcs->pdc_reg_vbase + PDC_INTSTATUS_OFFSET);
 
 	/* Wakeup IRQ thread */
-	tasklet_schedule(&pdcs->rx_tasklet);
+	queue_work(system_bh_wq, &pdcs->rx_work);
 	return IRQ_HANDLED;
 }
 
 /**
- * pdc_tasklet_cb() - Tasklet callback that runs the deferred processing after
+ * pdc_work_cb() - Work callback that runs the deferred processing after
  * a DMA receive interrupt. Reenables the receive interrupt.
  * @t: Pointer to the Altera sSGDMA channel structure
  */
-static void pdc_tasklet_cb(struct tasklet_struct *t)
+static void pdc_work_cb(struct work_struct *t)
 {
-	struct pdc_state *pdcs = from_tasklet(pdcs, t, rx_tasklet);
+	struct pdc_state *pdcs = from_work(pdcs, t, rx_work);
 
 	pdc_receive(pdcs);
 
@@ -1577,8 +1578,8 @@ static int pdc_probe(struct platform_device *pdev)
 
 	pdc_hw_init(pdcs);
 
-	/* Init tasklet for deferred DMA rx processing */
-	tasklet_setup(&pdcs->rx_tasklet, pdc_tasklet_cb);
+	/* Init work for deferred DMA rx processing */
+	INIT_WORK(&pdcs->rx_work, pdc_work_cb);
 
 	err = pdc_interrupts_init(pdcs);
 	if (err)
@@ -1595,7 +1596,7 @@ static int pdc_probe(struct platform_device *pdev)
 	return PDC_SUCCESS;
 
 cleanup_buf_pool:
-	tasklet_kill(&pdcs->rx_tasklet);
+	cancel_work_sync(&pdcs->rx_work);
 	dma_pool_destroy(pdcs->rx_buf_pool);
 
 cleanup_ring_pool:
@@ -1611,7 +1612,7 @@ static void pdc_remove(struct platform_device *pdev)
 
 	pdc_free_debugfs();
 
-	tasklet_kill(&pdcs->rx_tasklet);
+	cancel_work_sync(&pdcs->rx_work);
 
 	pdc_hw_disable(pdcs);
 

drivers/mailbox/imx-mailbox.c

@@ -21,6 +21,7 @@
 #include <linux/pm_runtime.h>
 #include <linux/suspend.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 
 #include "mailbox.h"
 
@@ -80,7 +81,7 @@ struct imx_mu_con_priv {
 	char			irq_desc[IMX_MU_CHAN_NAME_SIZE];
 	enum imx_mu_chan_type	type;
 	struct mbox_chan	*chan;
-	struct tasklet_struct	txdb_tasklet;
+	struct work_struct 	txdb_work;
 };
 
 struct imx_mu_priv {
@@ -232,7 +233,7 @@ static int imx_mu_generic_tx(struct imx_mu_priv *priv,
 		break;
 	case IMX_MU_TYPE_TXDB:
 		imx_mu_xcr_rmw(priv, IMX_MU_GCR, IMX_MU_xCR_GIRn(priv->dcfg->type, cp->idx), 0);
-		tasklet_schedule(&cp->txdb_tasklet);
+		queue_work(system_bh_wq, &cp->txdb_work);
 		break;
 	case IMX_MU_TYPE_TXDB_V2:
 		imx_mu_xcr_rmw(priv, IMX_MU_GCR, IMX_MU_xCR_GIRn(priv->dcfg->type, cp->idx), 0);
@@ -420,7 +421,7 @@ static int imx_mu_seco_tx(struct imx_mu_priv *priv, struct imx_mu_con_priv *cp,
 		}
 
 		/* Simulate hack for mbox framework */
-		tasklet_schedule(&cp->txdb_tasklet);
+		queue_work(system_bh_wq, &cp->txdb_work);
 
 		break;
 	default:
@@ -484,9 +485,9 @@ static int imx_mu_seco_rxdb(struct imx_mu_priv *priv, struct imx_mu_con_priv *cp
 	return err;
 }
 
-static void imx_mu_txdb_tasklet(unsigned long data)
+static void imx_mu_txdb_work(struct work_struct *t)
 {
-	struct imx_mu_con_priv *cp = (struct imx_mu_con_priv *)data;
+	struct imx_mu_con_priv *cp = from_work(cp, t, txdb_work);
 
 	mbox_chan_txdone(cp->chan, 0);
 }
@@ -570,8 +571,7 @@ static int imx_mu_startup(struct mbox_chan *chan)
 
 	if (cp->type == IMX_MU_TYPE_TXDB) {
 		/* Tx doorbell don't have ACK support */
-		tasklet_init(&cp->txdb_tasklet, imx_mu_txdb_tasklet,
-			     (unsigned long)cp);
+		INIT_WORK(&cp->txdb_work, imx_mu_txdb_work);
 		return 0;
 	}
 
@@ -615,7 +615,7 @@ static void imx_mu_shutdown(struct mbox_chan *chan)
 	}
 
 	if (cp->type == IMX_MU_TYPE_TXDB) {
-		tasklet_kill(&cp->txdb_tasklet);
+		cancel_work_sync(&cp->txdb_work);
 		pm_runtime_put_sync(priv->dev);
 		return;
 	}