Merge patch series "NCR5380: Bug fixes and other improvements"

Finn Thain <fthain@linux-m68k.org> says:

This series begins with some work on the mac_scsi driver to improve
compatibility with SCSI2SD v5 devices. Better error handling is needed
there because the PDMA hardware does not tolerate the write latency
spikes which SD cards can produce.

A bug is fixed in the 5380 core driver so that scatter/gather can be
enabled in mac_scsi.

Several patches at the end of this series improve robustness and
correctness in the core driver.

This series has been tested on a variety of mac_scsi hosts. A variety
of SCSI targets was also tested, including Quantum HDD, Fujitsu HDD,
Iomega FDD, Ricoh CD-RW, Matsushita CD-ROM, SCSI2SD and BlueSCSI.

Link: https://lore.kernel.org/r/cover.1723001788.git.fthain@linux-m68k.org
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 88 insertions, 82 deletions

diff --git a/drivers/scsi/mac_scsi.c b/drivers/scsi/mac_scsi.c
index 53ee8f84d094..f225bb20aa22 100644
--- a/drivers/scsi/mac_scsi.c
+++ b/drivers/scsi/mac_scsi.c
@@ -102,11 +102,15 @@ __setup("mac5380=", mac_scsi_setup);
  * Linux SCSI drivers lack knowledge of the timing behaviour of SCSI targets
  * so bus errors are unavoidable.
  *
- * If a MOVE.B instruction faults, we assume that zero bytes were transferred
- * and simply retry. That assumption probably depends on target behaviour but
- * seems to hold up okay. The NOP provides synchronization: without it the
- * fault can sometimes occur after the program counter has moved past the
- * offending instruction. Post-increment addressing can't be used.
+ * If a MOVE.B instruction faults during a receive operation, we assume the
+ * target sent nothing and try again. That assumption probably depends on
+ * target firmware but it seems to hold up okay. If a fault happens during a
+ * send operation, the target may or may not have seen /ACK and got the byte.
+ * It's uncertain so the whole SCSI command gets retried.
+ *
+ * The NOP is needed for synchronization because the fault address in the
+ * exception stack frame may or may not be the instruction that actually
+ * caused the bus error. Post-increment addressing can't be used.
  */
 
 #define MOVE_BYTE(operands) \
@@ -208,8 +212,6 @@ __setup("mac5380=", mac_scsi_setup);
 		".previous                     \n" \
 		: "+a" (addr), "+r" (n), "+r" (result) : "a" (io))
 
-#define MAC_PDMA_DELAY		32
-
 static inline int mac_pdma_recv(void __iomem *io, unsigned char *start, int n)
 {
 	unsigned char *addr = start;
@@ -245,22 +247,21 @@ static inline int mac_pdma_send(unsigned char *start, void __iomem *io, int n)
 	if (n >= 1) {
 		MOVE_BYTE("%0@,%3@");
 		if (result)
-			goto out;
+			return -1;
 	}
 	if (n >= 1 && ((unsigned long)addr & 1)) {
 		MOVE_BYTE("%0@,%3@");
 		if (result)
-			goto out;
+			return -2;
 	}
 	while (n >= 32)
 		MOVE_16_WORDS("%0@+,%3@");
 	while (n >= 2)
 		MOVE_WORD("%0@+,%3@");
 	if (result)
-		return start - addr; /* Negated to indicate uncertain length */
+		return start - addr - 1; /* Negated to indicate uncertain length */
 	if (n == 1)
 		MOVE_BYTE("%0@,%3@");
-out:
 	return addr - start;
 }
 
@@ -274,25 +275,56 @@ static inline void write_ctrl_reg(struct NCR5380_hostdata *hostdata, u32 value)
 	out_be32(hostdata->io + (CTRL_REG << 4), value);
 }
 
+static inline int macscsi_wait_for_drq(struct NCR5380_hostdata *hostdata)
+{
+	unsigned int n = 1; /* effectively multiplies NCR5380_REG_POLL_TIME */
+	unsigned char basr;
+
+again:
+	basr = NCR5380_read(BUS_AND_STATUS_REG);
+
+	if (!(basr & BASR_PHASE_MATCH))
+		return 1;
+
+	if (basr & BASR_IRQ)
+		return -1;
+
+	if (basr & BASR_DRQ)
+		return 0;
+
+	if (n-- == 0) {
+		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
+		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
+			 "%s: DRQ timeout\n", __func__);
+		return -1;
+	}
+
+	NCR5380_poll_politely2(hostdata,
+			       BUS_AND_STATUS_REG, BASR_DRQ, BASR_DRQ,
+			       BUS_AND_STATUS_REG, BASR_PHASE_MATCH, 0, 0);
+	goto again;
+}
+
 static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
                                 unsigned char *dst, int len)
 {
 	u8 __iomem *s = hostdata->pdma_io + (INPUT_DATA_REG << 4);
 	unsigned char *d = dst;
-	int result = 0;
 
 	hostdata->pdma_residual = len;
 
-	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                              BASR_DRQ | BASR_PHASE_MATCH,
-	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
-		int bytes;
+	while (macscsi_wait_for_drq(hostdata) == 0) {
+		int bytes, chunk_bytes;
 
 		if (macintosh_config->ident == MAC_MODEL_IIFX)
 			write_ctrl_reg(hostdata, CTRL_HANDSHAKE_MODE |
 			                         CTRL_INTERRUPTS_ENABLE);
 
-		bytes = mac_pdma_recv(s, d, min(hostdata->pdma_residual, 512));
+		chunk_bytes = min(hostdata->pdma_residual, 512);
+		bytes = mac_pdma_recv(s, d, chunk_bytes);
+
+		if (macintosh_config->ident == MAC_MODEL_IIFX)
+			write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
 
 		if (bytes > 0) {
 			d += bytes;
@@ -300,37 +332,25 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 		}
 
 		if (hostdata->pdma_residual == 0)
-			goto out;
+			break;
 
-		if (NCR5380_poll_politely2(hostdata, STATUS_REG, SR_REQ, SR_REQ,
-		                           BUS_AND_STATUS_REG, BASR_ACK,
-		                           BASR_ACK, 0) < 0)
-			scmd_printk(KERN_DEBUG, hostdata->connected,
-			            "%s: !REQ and !ACK\n", __func__);
-		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			goto out;
+		if (bytes > 0)
+			continue;
 
-		if (bytes == 0)
-			udelay(MAC_PDMA_DELAY);
+		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
+		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
+			 "%s: bus error [%d/%d] (%d/%d)\n",
+			 __func__, d - dst, len, bytes, chunk_bytes);
 
-		if (bytes >= 0)
+		if (bytes == 0)
 			continue;
 
-		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
-		         "%s: bus error (%d/%d)\n", __func__, d - dst, len);
-		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-		result = -1;
-		goto out;
+		if (macscsi_wait_for_drq(hostdata) <= 0)
+			set_host_byte(hostdata->connected, DID_ERROR);
+		break;
 	}
 
-	scmd_printk(KERN_ERR, hostdata->connected,
-	            "%s: phase mismatch or !DRQ\n", __func__);
-	NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-	result = -1;
-out:
-	if (macintosh_config->ident == MAC_MODEL_IIFX)
-		write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
-	return result;
+	return 0;
 }
 
 static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
@@ -338,67 +358,47 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 {
 	unsigned char *s = src;
 	u8 __iomem *d = hostdata->pdma_io + (OUTPUT_DATA_REG << 4);
-	int result = 0;
 
 	hostdata->pdma_residual = len;
 
-	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                              BASR_DRQ | BASR_PHASE_MATCH,
-	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
-		int bytes;
+	while (macscsi_wait_for_drq(hostdata) == 0) {
+		int bytes, chunk_bytes;
 
 		if (macintosh_config->ident == MAC_MODEL_IIFX)
 			write_ctrl_reg(hostdata, CTRL_HANDSHAKE_MODE |
 			                         CTRL_INTERRUPTS_ENABLE);
 
-		bytes = mac_pdma_send(s, d, min(hostdata->pdma_residual, 512));
+		chunk_bytes = min(hostdata->pdma_residual, 512);
+		bytes = mac_pdma_send(s, d, chunk_bytes);
+
+		if (macintosh_config->ident == MAC_MODEL_IIFX)
+			write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
 
 		if (bytes > 0) {
 			s += bytes;
 			hostdata->pdma_residual -= bytes;
 		}
 
-		if (hostdata->pdma_residual == 0) {
-			if (NCR5380_poll_politely(hostdata, TARGET_COMMAND_REG,
-			                          TCR_LAST_BYTE_SENT,
-			                          TCR_LAST_BYTE_SENT,
-			                          0) < 0) {
-				scmd_printk(KERN_ERR, hostdata->connected,
-				            "%s: Last Byte Sent timeout\n", __func__);
-				result = -1;
-			}
-			goto out;
-		}
+		if (hostdata->pdma_residual == 0)
+			break;
 
-		if (NCR5380_poll_politely2(hostdata, STATUS_REG, SR_REQ, SR_REQ,
-		                           BUS_AND_STATUS_REG, BASR_ACK,
-		                           BASR_ACK, 0) < 0)
-			scmd_printk(KERN_DEBUG, hostdata->connected,
-			            "%s: !REQ and !ACK\n", __func__);
-		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			goto out;
+		if (bytes > 0)
+			continue;
 
-		if (bytes == 0)
-			udelay(MAC_PDMA_DELAY);
+		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
+		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
+			 "%s: bus error [%d/%d] (%d/%d)\n",
+			 __func__, s - src, len, bytes, chunk_bytes);
 
-		if (bytes >= 0)
+		if (bytes == 0)
 			continue;
 
-		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
-		         "%s: bus error (%d/%d)\n", __func__, s - src, len);
-		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-		result = -1;
-		goto out;
+		if (macscsi_wait_for_drq(hostdata) <= 0)
+			set_host_byte(hostdata->connected, DID_ERROR);
+		break;
 	}
 
-	scmd_printk(KERN_ERR, hostdata->connected,
-	            "%s: phase mismatch or !DRQ\n", __func__);
-	NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-	result = -1;
-out:
-	if (macintosh_config->ident == MAC_MODEL_IIFX)
-		write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
-	return result;
+	return 0;
 }
 
 static int macscsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
@@ -432,7 +432,7 @@ static struct scsi_host_template mac_scsi_template = {
 	.eh_host_reset_handler	= macscsi_host_reset,
 	.can_queue		= 16,
 	.this_id		= 7,
-	.sg_tablesize		= 1,
+	.sg_tablesize		= SG_ALL,
 	.cmd_per_lun		= 2,
 	.dma_boundary		= PAGE_SIZE - 1,
 	.cmd_size		= sizeof(struct NCR5380_cmd),
@@ -470,6 +470,9 @@ static int __init mac_scsi_probe(struct platform_device *pdev)
 	if (setup_hostid >= 0)
 		mac_scsi_template.this_id = setup_hostid & 7;
 
+	if (macintosh_config->ident == MAC_MODEL_IIFX)
+		mac_scsi_template.sg_tablesize = 1;
+
 	instance = scsi_host_alloc(&mac_scsi_template,
 	                           sizeof(struct NCR5380_hostdata));
 	if (!instance)
@@ -491,6 +494,9 @@ static int __init mac_scsi_probe(struct platform_device *pdev)
 
 	host_flags |= setup_toshiba_delay > 0 ? FLAG_TOSHIBA_DELAY : 0;
 
+	if (instance->sg_tablesize > 1)
+		host_flags |= FLAG_DMA_FIXUP;
+
 	error = NCR5380_init(instance, host_flags | FLAG_LATE_DMA_SETUP);
 	if (error)
 		goto fail_init;