[PATCH v4 5/5] g_NCR5380: Re-work PDMA loops

[Finn Thain <fthain@telegraphics.com.au>]

From: Ondrej Zary <linux@rainbow-software.org>

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

On DTC chips, IRQ can arrive late and we miss it because we only check
once. Merge the IRQ check into host buffer wait 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
datasheet. Calculate residual from block count register instead of the
loop counter. Factor-out common code as wait_for_53c80_access(). -- F.T.]

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
---
 drivers/scsi/g_NCR5380.c | 147 ++++++++++++++++++++++-------------------------
 1 file changed, 69 insertions(+), 78 deletions(-)

diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c
index b1e0a08e49c1..a9e050b65d5f 100644
--- a/drivers/scsi/g_NCR5380.c
+++ b/drivers/scsi/g_NCR5380.c
@@ -482,6 +482,30 @@ 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 (hostdata->board == BOARD_DTC3181E)
+			udelay(4); /* DTC436 chip hangs without this */
+		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_pread - pseudo DMA receive
  * @hostdata: scsi host private data
@@ -494,18 +518,18 @@ static void generic_NCR5380_release_resources(struct Scsi_Host *instance)
 static inline int generic_NCR5380_pread(struct NCR5380_hostdata *hostdata,
                                         unsigned char *dst, int len)
 {
-	int blocks = len / 128;
 	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)
+	NCR5380_write(hostdata->c400_blk_cnt, len / 128);
+
+	while (start < len) {
+		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)
 			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 */
 
 		if (hostdata->io_port && hostdata->io_width == 2)
 			insw(hostdata->io_port + hostdata->c400_host_buf,
@@ -518,38 +542,19 @@ static inline int generic_NCR5380_pread(struct NCR5380_hostdata *hostdata,
 				hostdata->io + NCR53C400_host_buffer, 128);
 
 		start += 128;
-		blocks--;
 	}
 
-	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);
-
-		start += 128;
-		blocks--;
-	}
-
-	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;
+	hostdata->pdma_residual = NCR5380_read(hostdata->c400_blk_cnt) * 128;
 
-	/* wait for 53C80 registers to be available */
-	while (!(NCR5380_read(hostdata->c400_ctl_status) & CSR_53C80_REG))
-		;
+	if (start < len) {
+		/* Detected a 53c80 interrupt (or worse). Reset 53c400 logic. */
+		NCR5380_write(hostdata->c400_ctl_status, CSR_RESET);
+		NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
+	} else
+		wait_for_53c80_access(hostdata);
 
-	if (NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
+	if (hostdata->pdma_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 (%d)\n",
@@ -570,36 +575,18 @@ static inline int generic_NCR5380_pread(struct NCR5380_hostdata *hostdata,
 static inline int generic_NCR5380_pwrite(struct NCR5380_hostdata *hostdata,
                                          unsigned char *src, int len)
 {
-	int blocks = len / 128;
 	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;
-
-		if (NCR5380_read(hostdata->c400_blk_cnt) == 0)
+	NCR5380_write(hostdata->c400_blk_cnt, len / 128);
+
+	while (start < len) {
+		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)
 			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);
-
-		start += 128;
-		blocks--;
-	}
-	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)
 			outsw(hostdata->io_port + hostdata->c400_host_buf,
@@ -612,27 +599,31 @@ static inline int generic_NCR5380_pwrite(struct NCR5380_hostdata *hostdata,
 			            src + start, 128);
 
 		start += 128;
-		blocks--;
 	}
 
-out_wait:
-	hostdata->pdma_residual = len - start;
+	hostdata->pdma_residual = NCR5380_read(hostdata->c400_blk_cnt) * 128;
 
-	/* 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 (start < len) {
+		/* Detected a 53c80 interrupt (or worse). Reset 53c400 logic. */
+		NCR5380_write(hostdata->c400_ctl_status, CSR_RESET);
+		NCR5380_write(hostdata->c400_ctl_status, CSR_BASE);
+	} else
+		wait_for_53c80_access(hostdata);
+
+	if (hostdata->pdma_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 (%d)\n",
+			            __func__, hostdata->pdma_residual);
 	}
 
-	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);
-
 	return 0;
 }
 
-- 
2.13.0