aha1542: use a local bounce buffer

To remove the last user of the unchecked_isa_dma flag and thus the block
layer ISA bounce buffering switch this driver to use its own local bounce
buffer.  This has the effect of not needing the chain indirection and
supporting and unlimited number of segments.  It does however limit the
transfer size for each command to something that can be reasonable
allocated by dma_alloc_coherent like 8K.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210331073001.46776-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/scsi/aha1542.c

@@ -65,9 +65,12 @@ struct aha1542_hostdata {
 	dma_addr_t ccb_handle;
 };
 
+#define AHA1542_MAX_SECTORS       16
+
 struct aha1542_cmd {
-	struct chain *chain;
-	dma_addr_t chain_handle;
+	/* bounce buffer */
+	void *data_buffer;
+	dma_addr_t data_buffer_handle;
 };
 
 static inline void aha1542_intr_reset(u16 base)
@@ -257,15 +260,19 @@ static int aha1542_test_port(struct Scsi_Host *sh)
 static void aha1542_free_cmd(struct scsi_cmnd *cmd)
 {
 	struct aha1542_cmd *acmd = scsi_cmd_priv(cmd);
-	struct device *dev = cmd->device->host->dma_dev;
-	size_t len = scsi_sg_count(cmd) * sizeof(struct chain);
 
-	if (acmd->chain) {
-		dma_unmap_single(dev, acmd->chain_handle, len, DMA_TO_DEVICE);
-		kfree(acmd->chain);
+	if (cmd->sc_data_direction == DMA_FROM_DEVICE) {
+		void *buf = acmd->data_buffer;
+		struct req_iterator iter;
+		struct bio_vec bv;
+
+		rq_for_each_segment(bv, cmd->request, iter) {
+			memcpy_to_page(bv.bv_page, bv.bv_offset, buf,
+				       bv.bv_len);
+			buf += bv.bv_len;
+		}
 	}
 
-	acmd->chain = NULL;
 	scsi_dma_unmap(cmd);
 }
 
@@ -416,7 +423,7 @@ static int aha1542_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
 	u8 lun = cmd->device->lun;
 	unsigned long flags;
 	int bufflen = scsi_bufflen(cmd);
-	int mbo, sg_count;
+	int mbo;
 	struct mailbox *mb = aha1542->mb;
 	struct ccb *ccb = aha1542->ccb;
 
@@ -438,17 +445,17 @@ static int aha1542_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
 		print_hex_dump_bytes("command: ", DUMP_PREFIX_NONE, cmd->cmnd, cmd->cmd_len);
 	}
 #endif
-	sg_count = scsi_dma_map(cmd);
-	if (sg_count) {
-		size_t len = sg_count * sizeof(struct chain);
-
-		acmd->chain = kmalloc(len, GFP_DMA);
-		if (!acmd->chain)
-			goto out_unmap;
-		acmd->chain_handle = dma_map_single(sh->dma_dev, acmd->chain,
-				len, DMA_TO_DEVICE);
-		if (dma_mapping_error(sh->dma_dev, acmd->chain_handle))
-			goto out_free_chain;
+
+	if (cmd->sc_data_direction == DMA_TO_DEVICE) {
+		void *buf = acmd->data_buffer;
+		struct req_iterator iter;
+		struct bio_vec bv;
+
+		rq_for_each_segment(bv, cmd->request, iter) {
+			memcpy_from_page(buf, bv.bv_page, bv.bv_offset,
+					 bv.bv_len);
+			buf += bv.bv_len;
+		}
 	}
 
 	/*
@@ -496,27 +503,12 @@ static int aha1542_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
 		direction = 16;
 
 	memcpy(ccb[mbo].cdb, cmd->cmnd, ccb[mbo].cdblen);
-
-	if (bufflen) {
-		struct scatterlist *sg;
-		int i;
-
-		ccb[mbo].op = 2;	/* SCSI Initiator Command  w/scatter-gather */
-		scsi_for_each_sg(cmd, sg, sg_count, i) {
-			any2scsi(acmd->chain[i].dataptr, sg_dma_address(sg));
-			any2scsi(acmd->chain[i].datalen, sg_dma_len(sg));
-		};
-		any2scsi(ccb[mbo].datalen, sg_count * sizeof(struct chain));
-		any2scsi(ccb[mbo].dataptr, acmd->chain_handle);
-#ifdef DEBUG
-		shost_printk(KERN_DEBUG, sh, "cptr %p: ", acmd->chain);
-		print_hex_dump_bytes("cptr: ", DUMP_PREFIX_NONE, acmd->chain, 18);
-#endif
-	} else {
-		ccb[mbo].op = 0;	/* SCSI Initiator Command */
-		any2scsi(ccb[mbo].datalen, 0);
+	ccb[mbo].op = 0;	/* SCSI Initiator Command */
+	any2scsi(ccb[mbo].datalen, bufflen);
+	if (bufflen)
+		any2scsi(ccb[mbo].dataptr, acmd->data_buffer_handle);
+	else
 		any2scsi(ccb[mbo].dataptr, 0);
-	};
 	ccb[mbo].idlun = (target & 7) << 5 | direction | (lun & 7);	/*SCSI Target Id */
 	ccb[mbo].rsalen = 16;
 	ccb[mbo].linkptr[0] = ccb[mbo].linkptr[1] = ccb[mbo].linkptr[2] = 0;
@@ -531,12 +523,6 @@ static int aha1542_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *cmd)
 	spin_unlock_irqrestore(sh->host_lock, flags);
 
 	return 0;
-out_free_chain:
-	kfree(acmd->chain);
-	acmd->chain = NULL;
-out_unmap:
-	scsi_dma_unmap(cmd);
-	return SCSI_MLQUEUE_HOST_BUSY;
 }
 
 /* Initialize mailboxes */
@@ -1027,6 +1013,27 @@ static int aha1542_biosparam(struct scsi_device *sdev,
 }
 MODULE_LICENSE("GPL");
 
+static int aha1542_init_cmd_priv(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
+{
+	struct aha1542_cmd *acmd = scsi_cmd_priv(cmd);
+
+	acmd->data_buffer = dma_alloc_coherent(shost->dma_dev,
+			SECTOR_SIZE * AHA1542_MAX_SECTORS,
+			&acmd->data_buffer_handle, GFP_KERNEL);
+	if (!acmd->data_buffer)
+		return -ENOMEM;
+	return 0;
+}
+
+static int aha1542_exit_cmd_priv(struct Scsi_Host *shost, struct scsi_cmnd *cmd)
+{
+	struct aha1542_cmd *acmd = scsi_cmd_priv(cmd);
+
+	dma_free_coherent(shost->dma_dev, SECTOR_SIZE * AHA1542_MAX_SECTORS,
+			acmd->data_buffer, acmd->data_buffer_handle);
+	return 0;
+}
+
 static struct scsi_host_template driver_template = {
 	.module			= THIS_MODULE,
 	.proc_name		= "aha1542",
@@ -1037,10 +1044,12 @@ static struct scsi_host_template driver_template = {
 	.eh_bus_reset_handler	= aha1542_bus_reset,
 	.eh_host_reset_handler	= aha1542_host_reset,
 	.bios_param		= aha1542_biosparam,
+	.init_cmd_priv		= aha1542_init_cmd_priv,
+	.exit_cmd_priv		= aha1542_exit_cmd_priv,
 	.can_queue		= AHA1542_MAILBOXES,
 	.this_id		= 7,
-	.sg_tablesize		= 16,
-	.unchecked_isa_dma	= 1,
+	.max_sectors		= AHA1542_MAX_SECTORS,
+	.sg_tablesize		= SG_ALL,
 };
 
 static int aha1542_isa_match(struct device *pdev, unsigned int ndev)