linux-kernel - [PATCH 04/11] scsi: NCR5380: Check for phase match during PDMA fixup

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Message-Id: <99dc7d1f4c825621b5b120963a69f6cd3e9ca659.1723001788.git.fthain@linux-m68k.org>
Date: Wed, 07 Aug 2024 13:36:28 +1000
From: Finn Thain <fthain@...ux-m68k.org>
To: "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
    "Martin K. Petersen" <martin.petersen@...cle.com>
Cc: Hannes Reinecke <hare@...e.com>,
    Michael Schmitz <schmitzmic@...il.com>,
    Ondrej Zary <linux@...y.sk>,
    Stan Johnson <userm57@...oo.com>,
    linux-scsi@...r.kernel.org,
    linux-kernel@...r.kernel.org
Subject: [PATCH 04/11] scsi: NCR5380: Check for phase match during PDMA fixup

It's not an error for a target to change the bus phase during a transfer.
Unfortunately, the FLAG_DMA_FIXUP workaround does not allow for that --
a phase change produces a DRQ timeout error and the device borken flag
will be set.

Check the phase match bit during FLAG_DMA_FIXUP processing. Don't forget
to decrement the command residual. While we are here, change
shost_printk() into scmd_printk() for better consistency with other DMA
error messages.

Tested-by: Stan Johnson <userm57@...oo.com>
Fixes: 55181be8ced1 ("ncr5380: Replace redundant flags with FLAG_NO_DMA_FIXUP")
Signed-off-by: Finn Thain <fthain@...ux-m68k.org>
---
 drivers/scsi/NCR5380.c | 78 +++++++++++++++++++++---------------------
 1 file changed, 39 insertions(+), 39 deletions(-)

diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c
index cea3a79d538e..00e245173320 100644
--- a/drivers/scsi/NCR5380.c
+++ b/drivers/scsi/NCR5380.c
@@ -1485,6 +1485,7 @@ static int NCR5380_transfer_dma(struct Scsi_Host *instance,
 				unsigned char **data)
 {
 	struct NCR5380_hostdata *hostdata = shost_priv(instance);
+	struct NCR5380_cmd *ncmd = NCR5380_to_ncmd(hostdata->connected);
 	int c = *count;
 	unsigned char p = *phase;
 	unsigned char *d = *data;
@@ -1496,7 +1497,7 @@ static int NCR5380_transfer_dma(struct Scsi_Host *instance,
 		return -1;
 	}
 
-	NCR5380_to_ncmd(hostdata->connected)->phase = p;
+	ncmd->phase = p;
 
 	if (p & SR_IO) {
 		if (hostdata->read_overruns)
@@ -1608,45 +1609,44 @@ static int NCR5380_transfer_dma(struct Scsi_Host *instance,
  * request.
  */
 
-	if (hostdata->flags & FLAG_DMA_FIXUP) {
-		if (p & SR_IO) {
-			/*
-			 * The workaround was to transfer fewer bytes than we
-			 * intended to with the pseudo-DMA read function, wait for
-			 * the chip to latch the last byte, read it, and then disable
-			 * pseudo-DMA mode.
-			 *
-			 * After REQ is asserted, the NCR5380 asserts DRQ and ACK.
-			 * REQ is deasserted when ACK is asserted, and not reasserted
-			 * until ACK goes false.  Since the NCR5380 won't lower ACK
-			 * until DACK is asserted, which won't happen unless we twiddle
-			 * the DMA port or we take the NCR5380 out of DMA mode, we
-			 * can guarantee that we won't handshake another extra
-			 * byte.
-			 */
-
-			if (NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-			                          BASR_DRQ, BASR_DRQ, 0) < 0) {
-				result = -1;
-				shost_printk(KERN_ERR, instance, "PDMA read: DRQ timeout\n");
-			}
-			if (NCR5380_poll_politely(hostdata, STATUS_REG,
-			                          SR_REQ, 0, 0) < 0) {
-				result = -1;
-				shost_printk(KERN_ERR, instance, "PDMA read: !REQ timeout\n");
-			}
-			d[*count - 1] = NCR5380_read(INPUT_DATA_REG);
-		} else {
-			/*
-			 * Wait for the last byte to be sent.  If REQ is being asserted for
-			 * the byte we're interested, we'll ACK it and it will go false.
-			 */
-			if (NCR5380_poll_politely2(hostdata,
-			     BUS_AND_STATUS_REG, BASR_DRQ, BASR_DRQ,
-			     BUS_AND_STATUS_REG, BASR_PHASE_MATCH, 0, 0) < 0) {
-				result = -1;
-				shost_printk(KERN_ERR, instance, "PDMA write: DRQ and phase timeout\n");
+	if ((hostdata->flags & FLAG_DMA_FIXUP) &&
+	    (NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH)) {
+		/*
+		 * The workaround was to transfer fewer bytes than we
+		 * intended to with the pseudo-DMA receive function, wait for
+		 * the chip to latch the last byte, read it, and then disable
+		 * DMA mode.
+		 *
+		 * After REQ is asserted, the NCR5380 asserts DRQ and ACK.
+		 * REQ is deasserted when ACK is asserted, and not reasserted
+		 * until ACK goes false. Since the NCR5380 won't lower ACK
+		 * until DACK is asserted, which won't happen unless we twiddle
+		 * the DMA port or we take the NCR5380 out of DMA mode, we
+		 * can guarantee that we won't handshake another extra
+		 * byte.
+		 *
+		 * If sending, wait for the last byte to be sent. If REQ is
+		 * being asserted for the byte we're interested, we'll ACK it
+		 * and it will go false.
+		 */
+		if (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
+					   BASR_DRQ, BASR_DRQ, 0)) {
+			if ((p & SR_IO) &&
+			    (NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH)) {
+				if (!NCR5380_poll_politely(hostdata, STATUS_REG,
+							   SR_REQ, 0, 0)) {
+					d[c] = NCR5380_read(INPUT_DATA_REG);
+					--ncmd->this_residual;
+				} else {
+					result = -1;
+					scmd_printk(KERN_ERR, hostdata->connected,
+						    "PDMA fixup: !REQ timeout\n");
+				}
 			}
+		} else if (NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH) {
+			result = -1;
+			scmd_printk(KERN_ERR, hostdata->connected,
+				    "PDMA fixup: DRQ timeout\n");
 		}
 	}
 
-- 
2.39.5