[PATCH 00/11] NCR5380: Bug fixes and other improvements

[PATCH 00/11] NCR5380: Bug fixes and other improvements

[Finn Thain]

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.


Finn Thain (11):
  scsi: mac_scsi: Revise printk(KERN_DEBUG ...) messages
  scsi: mac_scsi: Refactor polling loop
  scsi: mac_scsi: Disallow bus errors during PDMA send
  scsi: NCR5380: Check for phase match during PDMA fixup
  scsi: mac_scsi: Enable scatter/gather by default
  scsi: NCR5380: Initialize buffer for MSG IN and STATUS transfers
  scsi: NCR5380: Handle BSY signal loss during information transfer
    phases
  scsi: NCR5380: Drop redundant member from struct NCR5380_cmd
  scsi: NCR5380: Remove redundant result calculation from
    NCR5380_transfer_pio()
  scsi: NCR5380: Remove obsolete comment
  scsi: NCR5380: Clean up indentation

 drivers/scsi/NCR5380.c   | 233 +++++++++++++++++++--------------------
 drivers/scsi/NCR5380.h   |  20 ++--
 drivers/scsi/mac_scsi.c  | 170 ++++++++++++++--------------
 drivers/scsi/sun3_scsi.c |   2 +-
 4 files changed, 215 insertions(+), 210 deletions(-)

-- 
2.39.5

[PATCH 01/11] scsi: mac_scsi: Revise printk(KERN_DEBUG ...) messages

[Finn Thain]

After a bus fault, capture and log the chip registers immediately,
if the NDEBUG_PSEUDO_DMA macro is defined. Remove some
printk(KERN_DEBUG ...) messages that aren't needed any more.
Don't skip the debug message when bytes == 0. Show all of the byte
counters in the debug messages.

Cc: stable@vger.kernel.org # 5.15+
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
This is not really a bug fix, but has been sent to @stable because it is a
prerequisite for the bug fixes which follow.
---
 drivers/scsi/mac_scsi.c | 42 +++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/drivers/scsi/mac_scsi.c b/drivers/scsi/mac_scsi.c
index a402c4dc4645..5ae8f4a1e9ca 100644
--- a/drivers/scsi/mac_scsi.c
+++ b/drivers/scsi/mac_scsi.c
@@ -286,13 +286,14 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
 	                              BASR_DRQ | BASR_PHASE_MATCH,
 	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
-		int bytes;
+		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 (bytes > 0) {
 			d += bytes;
@@ -302,23 +303,23 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 		if (hostdata->pdma_residual == 0)
 			goto out;
 
-		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)
 			udelay(MAC_PDMA_DELAY);
 
-		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);
+		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
+			 "%s: bus error [%d/%d] (%d/%d)\n",
+			 __func__, d - dst, len, bytes, chunk_bytes);
+
+		if (bytes == 0)
+			continue;
+
 		result = -1;
 		goto out;
 	}
@@ -345,13 +346,14 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
 	                              BASR_DRQ | BASR_PHASE_MATCH,
 	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
-		int bytes;
+		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 (bytes > 0) {
 			s += bytes;
@@ -370,23 +372,23 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 			goto out;
 		}
 
-		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)
 			udelay(MAC_PDMA_DELAY);
 
-		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);
+		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
+			 "%s: bus error [%d/%d] (%d/%d)\n",
+			 __func__, s - src, len, bytes, chunk_bytes);
+
+		if (bytes == 0)
+			continue;
+
 		result = -1;
 		goto out;
 	}
-- 
2.39.5

[PATCH 02/11] scsi: mac_scsi: Refactor polling loop

[Finn Thain]

Before the error handling can be revised, some preparation is needed.
Refactor the polling loop with a new function, macscsi_wait_for_drq().
This function will gain more call sites in the next patch.

Cc: stable@vger.kernel.org # 5.15+
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
This is not really a bug fix, but has been sent to @stable because it is a
prerequisite for the bug fixes which follow.
---
 drivers/scsi/mac_scsi.c | 80 +++++++++++++++++++++--------------------
 1 file changed, 42 insertions(+), 38 deletions(-)

diff --git a/drivers/scsi/mac_scsi.c b/drivers/scsi/mac_scsi.c
index 5ae8f4a1e9ca..39814c841113 100644
--- a/drivers/scsi/mac_scsi.c
+++ b/drivers/scsi/mac_scsi.c
@@ -208,8 +208,6 @@ __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;
@@ -274,6 +272,36 @@ 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)
 {
@@ -283,9 +311,7 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 
 	hostdata->pdma_residual = len;
 
-	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                              BASR_DRQ | BASR_PHASE_MATCH,
-	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
+	while (macscsi_wait_for_drq(hostdata) == 0) {
 		int bytes, chunk_bytes;
 
 		if (macintosh_config->ident == MAC_MODEL_IIFX)
@@ -295,19 +321,16 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 		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;
 			hostdata->pdma_residual -= bytes;
 		}
 
 		if (hostdata->pdma_residual == 0)
-			goto out;
-
-		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			goto out;
-
-		if (bytes == 0)
-			udelay(MAC_PDMA_DELAY);
+			break;
 
 		if (bytes > 0)
 			continue;
@@ -321,16 +344,9 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 			continue;
 
 		result = -1;
-		goto out;
+		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;
 }
 
@@ -343,9 +359,7 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 
 	hostdata->pdma_residual = len;
 
-	while (!NCR5380_poll_politely(hostdata, BUS_AND_STATUS_REG,
-	                              BASR_DRQ | BASR_PHASE_MATCH,
-	                              BASR_DRQ | BASR_PHASE_MATCH, 0)) {
+	while (macscsi_wait_for_drq(hostdata) == 0) {
 		int bytes, chunk_bytes;
 
 		if (macintosh_config->ident == MAC_MODEL_IIFX)
@@ -355,6 +369,9 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 		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;
@@ -369,15 +386,9 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 				            "%s: Last Byte Sent timeout\n", __func__);
 				result = -1;
 			}
-			goto out;
+			break;
 		}
 
-		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			goto out;
-
-		if (bytes == 0)
-			udelay(MAC_PDMA_DELAY);
-
 		if (bytes > 0)
 			continue;
 
@@ -390,16 +401,9 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 			continue;
 
 		result = -1;
-		goto out;
+		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;
 }
 
-- 
2.39.5

[PATCH 03/11] scsi: mac_scsi: Disallow bus errors during PDMA send

[Finn Thain]

SD cards can produce write latency spikes on the order of a hundred
milliseconds. If the target firmware does not hide that latency during
DATA IN and OUT phases it can cause the PDMA circuitry to raise a
processor bus fault which in turn leads to an unreliable byte count
and a DMA overrun.

The Last Byte Sent flag is used to detect the overrun but this mechanism
is unreliable on some systems. Instead, set a DID_ERROR result whenever
there is a bus fault during a PDMA send, unless the cause was a phase
mismatch.

Cc: stable@vger.kernel.org # 5.15+
Reported-and-tested-by: Stan Johnson <userm57@yahoo.com>
Fixes: 7c1f3e3447a1 ("scsi: mac_scsi: Treat Last Byte Sent time-out as failure")
Signed-off-by: Finn Thain <fthain@linux-m68k.org>
---
 drivers/scsi/mac_scsi.c | 44 ++++++++++++++++++-----------------------
 1 file changed, 19 insertions(+), 25 deletions(-)

diff --git a/drivers/scsi/mac_scsi.c b/drivers/scsi/mac_scsi.c
index 39814c841113..2e9fad1e3069 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) \
@@ -243,22 +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;
 }
 
@@ -307,7 +310,6 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 {
 	u8 __iomem *s = hostdata->pdma_io + (INPUT_DATA_REG << 4);
 	unsigned char *d = dst;
-	int result = 0;
 
 	hostdata->pdma_residual = len;
 
@@ -343,11 +345,12 @@ static inline int macscsi_pread(struct NCR5380_hostdata *hostdata,
 		if (bytes == 0)
 			continue;
 
-		result = -1;
+		if (macscsi_wait_for_drq(hostdata) <= 0)
+			set_host_byte(hostdata->connected, DID_ERROR);
 		break;
 	}
 
-	return result;
+	return 0;
 }
 
 static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
@@ -355,7 +358,6 @@ 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;
 
@@ -377,17 +379,8 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 			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;
-			}
+		if (hostdata->pdma_residual == 0)
 			break;
-		}
 
 		if (bytes > 0)
 			continue;
@@ -400,11 +393,12 @@ static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
 		if (bytes == 0)
 			continue;
 
-		result = -1;
+		if (macscsi_wait_for_drq(hostdata) <= 0)
+			set_host_byte(hostdata->connected, DID_ERROR);
 		break;
 	}
 
-	return result;
+	return 0;
 }
 
 static int macscsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
-- 
2.39.5

Re: [PATCH 00/11] NCR5380: Bug fixes and other improvements

[Martin K. Petersen]

Finn,

> 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.

Applied to 6.12/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: [PATCH 00/11] NCR5380: Bug fixes and other improvements

[Martin K. Petersen]

On Wed, 07 Aug 2024 13:36:28 +1000, Finn Thain wrote:

> 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.
> 
> [...]

Applied to 6.12/scsi-queue, thanks!

[01/11] scsi: mac_scsi: Revise printk(KERN_DEBUG ...) messages
        https://git.kernel.org/mkp/scsi/c/5ec4f820cb97
[02/11] scsi: mac_scsi: Refactor polling loop
        https://git.kernel.org/mkp/scsi/c/5545c3165cbc
[03/11] scsi: mac_scsi: Disallow bus errors during PDMA send
        https://git.kernel.org/mkp/scsi/c/5551bc30e4a6
[04/11] scsi: NCR5380: Check for phase match during PDMA fixup
        https://git.kernel.org/mkp/scsi/c/5768718da941
[05/11] scsi: mac_scsi: Enable scatter/gather by default
        https://git.kernel.org/mkp/scsi/c/2ac6d29716cd
[06/11] scsi: NCR5380: Initialize buffer for MSG IN and STATUS transfers
        https://git.kernel.org/mkp/scsi/c/1c71065df2df
[07/11] scsi: NCR5380: Handle BSY signal loss during information transfer phases
        https://git.kernel.org/mkp/scsi/c/086c4802cf99
[08/11] scsi: NCR5380: Drop redundant member from struct NCR5380_cmd
        https://git.kernel.org/mkp/scsi/c/476f8c82e218
[09/11] scsi: NCR5380: Remove redundant result calculation from NCR5380_transfer_pio()
        https://git.kernel.org/mkp/scsi/c/8663cadefd15
[10/11] scsi: NCR5380: Remove obsolete comment
        https://git.kernel.org/mkp/scsi/c/c331df3d4a8d
[11/11] scsi: NCR5380: Clean up indentation
        https://git.kernel.org/mkp/scsi/c/a8ebca904f8e

-- 
Martin K. Petersen	Oracle Linux Engineering