scsi: g_NCR5380: Re-work PDMA loops

The polling loops in pread() and pwrite() can easily become infinite
loops and hang the machine.

Merge the IRQ check into host buffer wait loop and add polling limit.

Also place a limit on polling for 53C80 registers accessibility.

[Use NCR5380_poll_politely2() for register polling. Rely on polling for
gated IRQ rather than polling for phase error, like the algorithm in the
53c400 datasheet. Move DTC436 workarounds into a separate patch.
Factor-out common code as wait_for_53c80_access(). Rework the residual
calculations. -- F.T.]
Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/g_NCR5380.c

@@ -480,6 +480,28 @@ static void generic_NCR5380_release_resources(struct Scsi_Host *instance)
 		release_mem_region(base, region_size);
 }
 
+/* wait_for_53c80_access - wait for 53C80 registers to become accessible
+ * @hostdata: scsi host private data
+ *
+ * The registers within the 53C80 logic block are inaccessible until
+ * bit 7 in the 53C400 control status register gets asserted.
+ */
+
+static void wait_for_53c80_access(struct NCR5380_hostdata *hostdata)
+{
+	int count = 10000;
+
+	do {
+		if (NCR5380_read(hostdata->c400_ctl_status) & CSR_53C80_REG)
+			return;
+	} while (--count > 0);
+
+	scmd_printk(KERN_ERR, hostdata->connected,
+	            "53c80 registers not accessible, device will be reset\n");
+	NCR5380_write(hostdata->c400_ctl_status, CSR_RESET);
+	NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
+}
+
 /**
  * generic_NCR5380_precv - pseudo DMA receive
  * @hostdata: scsi host private data
@@ -492,18 +514,27 @@ static void generic_NCR5380_release_resources(struct Scsi_Host *instance)
 static inline int generic_NCR5380_precv(struct NCR5380_hostdata *hostdata,
                                         unsigned char *dst, int len)
 {
-	int blocks = len / 128;
+	int residual;
 	int start = 0;
 
 	NCR5380_write(hostdata->c400_ctl_status, CSR_BASE | CSR_TRANS_DIR);
-	NCR5380_write(hostdata->c400_blk_cnt, blocks);
-	while (1) {
-		if (NCR5380_read(hostdata->c400_blk_cnt) == 0)
-			break;
-		if (NCR5380_read(hostdata->c400_ctl_status) & CSR_GATED_53C80_IRQ)
-			goto out_wait;
-		while (NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY)
-			; /* FIXME - no timeout */
+	NCR5380_write(hostdata->c400_blk_cnt, len / 128);
+
+	do {
+		if (start == len - 128) {
+			/* Ignore End of DMA interrupt for the final buffer */
+			if (NCR5380_poll_politely(hostdata, hostdata->c400_ctl_status,
+			                          CSR_HOST_BUF_NOT_RDY, 0, HZ / 64) < 0)
+				break;
+		} else {
+			if (NCR5380_poll_politely2(hostdata, hostdata->c400_ctl_status,
+			                           CSR_HOST_BUF_NOT_RDY, 0,
+			                           hostdata->c400_ctl_status,
+			                           CSR_GATED_53C80_IRQ,
+			                           CSR_GATED_53C80_IRQ, HZ / 64) < 0 ||
+			    NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY)
+				break;
+		}
 
 		if (hostdata->io_port && hostdata->io_width == 2)
 			insw(hostdata->io_port + hostdata->c400_host_buf,
@@ -514,44 +545,26 @@ static inline int generic_NCR5380_precv(struct NCR5380_hostdata *hostdata,
 		else
 			memcpy_fromio(dst + start,
 				hostdata->io + NCR53C400_host_buffer, 128);
-
 		start += 128;
-		blocks--;
-	}
+	} while (start < len);
 
-	if (blocks) {
-		while (NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY)
-			; /* FIXME - no timeout */
-
-		if (hostdata->io_port && hostdata->io_width == 2)
-			insw(hostdata->io_port + hostdata->c400_host_buf,
-							dst + start, 64);
-		else if (hostdata->io_port)
-			insb(hostdata->io_port + hostdata->c400_host_buf,
-							dst + start, 128);
-		else
-			memcpy_fromio(dst + start,
-				hostdata->io + NCR53C400_host_buffer, 128);
+	residual = len - start;
 
-		start += 128;
-		blocks--;
+	if (residual != 0) {
+		/* 53c80 interrupt or transfer timeout. Reset 53c400 logic. */
+		NCR5380_write(hostdata->c400_ctl_status, CSR_RESET);
+		NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
 	}
+	wait_for_53c80_access(hostdata);
 
-	if (!(NCR5380_read(hostdata->c400_ctl_status) & CSR_GATED_53C80_IRQ))
-		printk("53C400r: no 53C80 gated irq after transfer");
-
-out_wait:
-	hostdata->pdma_residual = len - start;
+	if (residual == 0 && NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
+	                                           BASR_END_DMA_TRANSFER,
+	                                           BASR_END_DMA_TRANSFER,
+	                                           HZ / 64) < 0)
+		scmd_printk(KERN_ERR, hostdata->connected, "%s: End of DMA timeout\n",
+		            __func__);
 
-	/* wait for 53C80 registers to be available */
-	while (!(NCR5380_read(hostdata->c400_ctl_status) & CSR_53C80_REG))
-		;
-
-	if (NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                          BASR_END_DMA_TRANSFER, BASR_END_DMA_TRANSFER,
-	                          HZ / 64) < 0)
-		scmd_printk(KERN_ERR, hostdata->connected, "%s: End of DMA timeout (%d)\n",
-		            __func__, hostdata->pdma_residual);
+	hostdata->pdma_residual = residual;
 
 	return 0;
 }
@@ -568,36 +581,39 @@ static inline int generic_NCR5380_precv(struct NCR5380_hostdata *hostdata,
 static inline int generic_NCR5380_psend(struct NCR5380_hostdata *hostdata,
                                         unsigned char *src, int len)
 {
-	int blocks = len / 128;
+	int residual;
 	int start = 0;
 
 	NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
-	NCR5380_write(hostdata->c400_blk_cnt, blocks);
-	while (1) {
-		if (NCR5380_read(hostdata->c400_ctl_status) & CSR_GATED_53C80_IRQ)
-			goto out_wait;
+	NCR5380_write(hostdata->c400_blk_cnt, len / 128);
+
+	do {
+		if (NCR5380_poll_politely2(hostdata, hostdata->c400_ctl_status,
+		                           CSR_HOST_BUF_NOT_RDY, 0,
+		                           hostdata->c400_ctl_status,
+		                           CSR_GATED_53C80_IRQ,
+		                           CSR_GATED_53C80_IRQ, HZ / 64) < 0 ||
+		    NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY) {
+			/* Both 128 B buffers are in use */
+			if (start >= 128)
+				start -= 128;
+			if (start >= 128)
+				start -= 128;
+			break;
+		}
 
-		if (NCR5380_read(hostdata->c400_blk_cnt) == 0)
+		if (start >= len && NCR5380_read(hostdata->c400_blk_cnt) == 0)
 			break;
-		while (NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY)
-			; // FIXME - timeout
 
-		if (hostdata->io_port && hostdata->io_width == 2)
-			outsw(hostdata->io_port + hostdata->c400_host_buf,
-							src + start, 64);
-		else if (hostdata->io_port)
-			outsb(hostdata->io_port + hostdata->c400_host_buf,
-							src + start, 128);
-		else
-			memcpy_toio(hostdata->io + NCR53C400_host_buffer,
-			            src + start, 128);
+		if (NCR5380_read(hostdata->c400_ctl_status) & CSR_GATED_53C80_IRQ) {
+			/* Host buffer is empty, other one is in use */
+			if (start >= 128)
+				start -= 128;
+			break;
+		}
 
-		start += 128;
-		blocks--;
-	}
-	if (blocks) {
-		while (NCR5380_read(hostdata->c400_ctl_status) & CSR_HOST_BUF_NOT_RDY)
-			; // FIXME - no timeout
+		if (start >= len)
+			continue;
 
 		if (hostdata->io_port && hostdata->io_width == 2)
 			outsw(hostdata->io_port + hostdata->c400_host_buf,
@@ -608,28 +624,33 @@ static inline int generic_NCR5380_psend(struct NCR5380_hostdata *hostdata,
 		else
 			memcpy_toio(hostdata->io + NCR53C400_host_buffer,
 			            src + start, 128);
-
 		start += 128;
-		blocks--;
-	}
+	} while (1);
 
-out_wait:
-	hostdata->pdma_residual = len - start;
+	residual = len - start;
 
-	/* wait for 53C80 registers to be available */
-	while (!(NCR5380_read(hostdata->c400_ctl_status) & CSR_53C80_REG)) {
-		udelay(4); /* DTC436 chip hangs without this */
-		/* FIXME - no timeout */
+	if (residual != 0) {
+		/* 53c80 interrupt or transfer timeout. Reset 53c400 logic. */
+		NCR5380_write(hostdata->c400_ctl_status, CSR_RESET);
+		NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
+	}
+	wait_for_53c80_access(hostdata);
+
+	if (residual == 0) {
+		if (NCR5380_poll_politely(hostdata, TARGET_COMMAND_REG,
+		                          TCR_LAST_BYTE_SENT, TCR_LAST_BYTE_SENT,
+		                          HZ / 64) < 0)
+			scmd_printk(KERN_ERR, hostdata->connected,
+			            "%s: Last Byte Sent timeout\n", __func__);
+
+		if (NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
+		                          BASR_END_DMA_TRANSFER, BASR_END_DMA_TRANSFER,
+		                          HZ / 64) < 0)
+			scmd_printk(KERN_ERR, hostdata->connected, "%s: End of DMA timeout\n",
+			            __func__);
 	}
 
-	while (!(NCR5380_read(TARGET_COMMAND_REG) & TCR_LAST_BYTE_SENT))
-		; 	// TIMEOUT
-
-	if (NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                          BASR_END_DMA_TRANSFER, BASR_END_DMA_TRANSFER,
-	                          HZ / 64) < 0)
-		scmd_printk(KERN_ERR, hostdata->connected, "%s: End of DMA timeout (%d)\n",
-		            __func__, hostdata->pdma_residual);
+	hostdata->pdma_residual = residual;
 
 	return 0;
 }