Merge tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI updates from James Bottomley:
 "This is mostly update of the usual drivers: qla2xxx, hpsa, lpfc, ufs,
  mpt3sas, ibmvscsi, megaraid_sas, bnx2fc and hisi_sas as well as the
  removal of the osst driver (I heard from Willem privately that he
  would like the driver removed because all his test hardware has
  failed). Plus number of minor changes, spelling fixes and other
  trivia.

  The big merge conflict this time around is the SPDX licence tags.
  Following discussion on linux-next, we believe our version to be more
  accurate than the one in the tree, so the resolution is to take our
  version for all the SPDX conflicts"

Note on the SPDX license tag conversion conflicts: the SCSI tree had
done its own SPDX conversion, which in some cases conflicted with the
treewide ones done by Thomas & co.

In almost all cases, the conflicts were purely syntactic: the SCSI tree
used the old-style SPDX tags ("GPL-2.0" and "GPL-2.0+") while the
treewide conversion had used the new-style ones ("GPL-2.0-only" and
"GPL-2.0-or-later").

In these cases I picked the new-style one.

In a few cases, the SPDX conversion was actually different, though.  As
explained by James above, and in more detail in a pre-pull-request
thread:

 "The other problem is actually substantive: In the libsas code Luben
  Tuikov originally specified gpl 2.0 only by dint of stating:

  * This file is licensed under GPLv2.

  In all the libsas files, but then muddied the water by quoting GPLv2
  verbatim (which includes the or later than language). So for these
  files Christoph did the conversion to v2 only SPDX tags and Thomas
  converted to v2 or later tags"

So in those cases, where the spdx tag substantially mattered, I took the
SCSI tree conversion of it, but then also took the opportunity to turn
the old-style "GPL-2.0" into a new-style "GPL-2.0-only" tag.

Similarly, when there were whitespace differences or other differences
to the comments around the copyright notices, I took the version from
the SCSI tree as being the more specific conversion.

Finally, in the spdx conversions that had no conflicts (because the
treewide ones hadn't been done for those files), I just took the SCSI
tree version as-is, even if it was old-style.  The old-style conversions
are perfectly valid, even if the "-only" and "-or-later" versions are
perhaps more descriptive.

* tag 'scsi-misc' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi: (185 commits)
  scsi: qla2xxx: move IO flush to the front of NVME rport unregistration
  scsi: qla2xxx: Fix NVME cmd and LS cmd timeout race condition
  scsi: qla2xxx: on session delete, return nvme cmd
  scsi: qla2xxx: Fix kernel crash after disconnecting NVMe devices
  scsi: megaraid_sas: Update driver version to 07.710.06.00-rc1
  scsi: megaraid_sas: Introduce various Aero performance modes
  scsi: megaraid_sas: Use high IOPS queues based on IO workload
  scsi: megaraid_sas: Set affinity for high IOPS reply queues
  scsi: megaraid_sas: Enable coalescing for high IOPS queues
  scsi: megaraid_sas: Add support for High IOPS queues
  scsi: megaraid_sas: Add support for MPI toolbox commands
  scsi: megaraid_sas: Offload Aero RAID5/6 division calculations to driver
  scsi: megaraid_sas: RAID1 PCI bandwidth limit algorithm is applicable for only Ventura
  scsi: megaraid_sas: megaraid_sas: Add check for count returned by HOST_DEVICE_LIST DCMD
  scsi: megaraid_sas: Handle sequence JBOD map failure at driver level
  scsi: megaraid_sas: Don't send FPIO to RL Bypass queue
  scsi: megaraid_sas: In probe context, retry IOC INIT once if firmware is in fault
  scsi: megaraid_sas: Release Mutex lock before OCR in case of DCMD timeout
  scsi: megaraid_sas: Call disable_irq from process IRQ poll
  scsi: megaraid_sas: Remove few debug counters from IO path
  ...

1 files changed, 260 insertions, 161 deletions

diff --git a/drivers/scsi/mac_scsi.c b/drivers/scsi/mac_scsi.c
index dba9517d9553..9c5566217ef6 100644
--- a/drivers/scsi/mac_scsi.c
+++ b/drivers/scsi/mac_scsi.c
@@ -4,6 +4,8 @@
  *
  * Copyright 1998, Michael Schmitz <mschmitz@lbl.gov>
  *
+ * Copyright 2019 Finn Thain
+ *
  * derived in part from:
  */
 /*
@@ -12,6 +14,7 @@
  * Copyright 1995, Russell King
  */
 
+#include <linux/delay.h>
 #include <linux/types.h>
 #include <linux/module.h>
 #include <linux/ioport.h>
@@ -22,6 +25,7 @@
 
 #include <asm/hwtest.h>
 #include <asm/io.h>
+#include <asm/macintosh.h>
 #include <asm/macints.h>
 #include <asm/setup.h>
 
@@ -53,7 +57,7 @@ static int setup_cmd_per_lun = -1;
 module_param(setup_cmd_per_lun, int, 0);
 static int setup_sg_tablesize = -1;
 module_param(setup_sg_tablesize, int, 0);
-static int setup_use_pdma = -1;
+static int setup_use_pdma = 512;
 module_param(setup_use_pdma, int, 0);
 static int setup_hostid = -1;
 module_param(setup_hostid, int, 0);
@@ -90,223 +94,318 @@ static int __init mac_scsi_setup(char *str)
 __setup("mac5380=", mac_scsi_setup);
 #endif /* !MODULE */
 
-/* Pseudo DMA asm originally by Ove Edlund */
-
-#define CP_IO_TO_MEM(s,d,n)				\
-__asm__ __volatile__					\
-    ("    cmp.w  #4,%2\n"				\
-     "    bls    8f\n"					\
-     "    move.w %1,%%d0\n"				\
-     "    neg.b  %%d0\n"				\
-     "    and.w  #3,%%d0\n"				\
-     "    sub.w  %%d0,%2\n"				\
-     "    bra    2f\n"					\
-     " 1: move.b (%0),(%1)+\n"				\
-     " 2: dbf    %%d0,1b\n"				\
-     "    move.w %2,%%d0\n"				\
-     "    lsr.w  #5,%%d0\n"				\
-     "    bra    4f\n"					\
-     " 3: move.l (%0),(%1)+\n"				\
-     "31: move.l (%0),(%1)+\n"				\
-     "32: move.l (%0),(%1)+\n"				\
-     "33: move.l (%0),(%1)+\n"				\
-     "34: move.l (%0),(%1)+\n"				\
-     "35: move.l (%0),(%1)+\n"				\
-     "36: move.l (%0),(%1)+\n"				\
-     "37: move.l (%0),(%1)+\n"				\
-     " 4: dbf    %%d0,3b\n"				\
-     "    move.w %2,%%d0\n"				\
-     "    lsr.w  #2,%%d0\n"				\
-     "    and.w  #7,%%d0\n"				\
-     "    bra    6f\n"					\
-     " 5: move.l (%0),(%1)+\n"				\
-     " 6: dbf    %%d0,5b\n"				\
-     "    and.w  #3,%2\n"				\
-     "    bra    8f\n"					\
-     " 7: move.b (%0),(%1)+\n"				\
-     " 8: dbf    %2,7b\n"				\
-     "    moveq.l #0, %2\n"				\
-     " 9: \n"						\
-     ".section .fixup,\"ax\"\n"				\
-     "    .even\n"					\
-     "91: moveq.l #1, %2\n"				\
-     "    jra 9b\n"					\
-     "94: moveq.l #4, %2\n"				\
-     "    jra 9b\n"					\
-     ".previous\n"					\
-     ".section __ex_table,\"a\"\n"			\
-     "   .align 4\n"					\
-     "   .long  1b,91b\n"				\
-     "   .long  3b,94b\n"				\
-     "   .long 31b,94b\n"				\
-     "   .long 32b,94b\n"				\
-     "   .long 33b,94b\n"				\
-     "   .long 34b,94b\n"				\
-     "   .long 35b,94b\n"				\
-     "   .long 36b,94b\n"				\
-     "   .long 37b,94b\n"				\
-     "   .long  5b,94b\n"				\
-     "   .long  7b,91b\n"				\
-     ".previous"					\
-     : "=a"(s), "=a"(d), "=d"(n)			\
-     : "0"(s), "1"(d), "2"(n)				\
-     : "d0")
+/*
+ * According to "Inside Macintosh: Devices", Mac OS requires disk drivers to
+ * specify the number of bytes between the delays expected from a SCSI target.
+ * This allows the operating system to "prevent bus errors when a target fails
+ * to deliver the next byte within the processor bus error timeout period."
+ * 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.
+ */
+
+#define MOVE_BYTE(operands) \
+	asm volatile ( \
+		"1:     moveb " operands "     \n" \
+		"11:    nop                    \n" \
+		"       addq #1,%0             \n" \
+		"       subq #1,%1             \n" \
+		"40:                           \n" \
+		"                              \n" \
+		".section .fixup,\"ax\"        \n" \
+		".even                         \n" \
+		"90:    movel #1, %2           \n" \
+		"       jra 40b                \n" \
+		".previous                     \n" \
+		"                              \n" \
+		".section __ex_table,\"a\"     \n" \
+		".align  4                     \n" \
+		".long   1b,90b                \n" \
+		".long  11b,90b                \n" \
+		".previous                     \n" \
+		: "+a" (addr), "+r" (n), "+r" (result) : "a" (io))
+
+/*
+ * If a MOVE.W (or MOVE.L) instruction faults, it cannot be retried because
+ * the residual byte count would be uncertain. In that situation the MOVE_WORD
+ * macro clears n in the fixup section to abort the transfer.
+ */
+
+#define MOVE_WORD(operands) \
+	asm volatile ( \
+		"1:     movew " operands "     \n" \
+		"11:    nop                    \n" \
+		"       subq #2,%1             \n" \
+		"40:                           \n" \
+		"                              \n" \
+		".section .fixup,\"ax\"        \n" \
+		".even                         \n" \
+		"90:    movel #0, %1           \n" \
+		"       movel #2, %2           \n" \
+		"       jra 40b                \n" \
+		".previous                     \n" \
+		"                              \n" \
+		".section __ex_table,\"a\"     \n" \
+		".align  4                     \n" \
+		".long   1b,90b                \n" \
+		".long  11b,90b                \n" \
+		".previous                     \n" \
+		: "+a" (addr), "+r" (n), "+r" (result) : "a" (io))
+
+#define MOVE_16_WORDS(operands) \
+	asm volatile ( \
+		"1:     movew " operands "     \n" \
+		"2:     movew " operands "     \n" \
+		"3:     movew " operands "     \n" \
+		"4:     movew " operands "     \n" \
+		"5:     movew " operands "     \n" \
+		"6:     movew " operands "     \n" \
+		"7:     movew " operands "     \n" \
+		"8:     movew " operands "     \n" \
+		"9:     movew " operands "     \n" \
+		"10:    movew " operands "     \n" \
+		"11:    movew " operands "     \n" \
+		"12:    movew " operands "     \n" \
+		"13:    movew " operands "     \n" \
+		"14:    movew " operands "     \n" \
+		"15:    movew " operands "     \n" \
+		"16:    movew " operands "     \n" \
+		"17:    nop                    \n" \
+		"       subl  #32,%1           \n" \
+		"40:                           \n" \
+		"                              \n" \
+		".section .fixup,\"ax\"        \n" \
+		".even                         \n" \
+		"90:    movel #0, %1           \n" \
+		"       movel #2, %2           \n" \
+		"       jra 40b                \n" \
+		".previous                     \n" \
+		"                              \n" \
+		".section __ex_table,\"a\"     \n" \
+		".align  4                     \n" \
+		".long   1b,90b                \n" \
+		".long   2b,90b                \n" \
+		".long   3b,90b                \n" \
+		".long   4b,90b                \n" \
+		".long   5b,90b                \n" \
+		".long   6b,90b                \n" \
+		".long   7b,90b                \n" \
+		".long   8b,90b                \n" \
+		".long   9b,90b                \n" \
+		".long  10b,90b                \n" \
+		".long  11b,90b                \n" \
+		".long  12b,90b                \n" \
+		".long  13b,90b                \n" \
+		".long  14b,90b                \n" \
+		".long  15b,90b                \n" \
+		".long  16b,90b                \n" \
+		".long  17b,90b                \n" \
+		".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;
+	int result = 0;
+
+	if (n >= 1) {
+		MOVE_BYTE("%3@,%0@");
+		if (result)
+			goto out;
+	}
+	if (n >= 1 && ((unsigned long)addr & 1)) {
+		MOVE_BYTE("%3@,%0@");
+		if (result)
+			goto out;
+	}
+	while (n >= 32)
+		MOVE_16_WORDS("%3@,%0@+");
+	while (n >= 2)
+		MOVE_WORD("%3@,%0@+");
+	if (result)
+		return start - addr; /* Negated to indicate uncertain length */
+	if (n == 1)
+		MOVE_BYTE("%3@,%0@");
+out:
+	return addr - start;
+}
+
+static inline int mac_pdma_send(unsigned char *start, void __iomem *io, int n)
+{
+	unsigned char *addr = start;
+	int result = 0;
+
+	if (n >= 1) {
+		MOVE_BYTE("%0@,%3@");
+		if (result)
+			goto out;
+	}
+	if (n >= 1 && ((unsigned long)addr & 1)) {
+		MOVE_BYTE("%0@,%3@");
+		if (result)
+			goto out;
+	}
+	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 */
+	if (n == 1)
+		MOVE_BYTE("%0@,%3@");
+out:
+	return addr - start;
+}
+
+/* The "SCSI DMA" chip on the IIfx implements this register. */
+#define CTRL_REG                0x8
+#define CTRL_INTERRUPTS_ENABLE  BIT(1)
+#define CTRL_HANDSHAKE_MODE     BIT(3)
+
+static inline void write_ctrl_reg(struct NCR5380_hostdata *hostdata, u32 value)
+{
+	out_be32(hostdata->io + (CTRL_REG << 4), value);
+}
 
 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 n = len;
-	int transferred;
+	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, HZ / 64)) {
-		CP_IO_TO_MEM(s, d, n);
+		int bytes;
+
+		if (macintosh_config->ident == MAC_MODEL_IIFX)
+			write_ctrl_reg(hostdata, CTRL_HANDSHAKE_MODE |
+			                         CTRL_INTERRUPTS_ENABLE);
 
-		transferred = d - dst - n;
-		hostdata->pdma_residual = len - transferred;
+		bytes = mac_pdma_recv(s, d, min(hostdata->pdma_residual, 512));
 
-		/* No bus error. */
-		if (n == 0)
-			return 0;
+		if (bytes > 0) {
+			d += bytes;
+			hostdata->pdma_residual -= bytes;
+		}
+
+		if (hostdata->pdma_residual == 0)
+			goto out;
 
-		/* Target changed phase early? */
 		if (NCR5380_poll_politely2(hostdata, STATUS_REG, SR_REQ, SR_REQ,
-		                           BUS_AND_STATUS_REG, BASR_ACK, BASR_ACK, HZ / 64) < 0)
-			scmd_printk(KERN_ERR, hostdata->connected,
+		                           BUS_AND_STATUS_REG, BASR_ACK,
+		                           BASR_ACK, HZ / 64) < 0)
+			scmd_printk(KERN_DEBUG, hostdata->connected,
 			            "%s: !REQ and !ACK\n", __func__);
 		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			return 0;
+			goto out;
+
+		if (bytes == 0)
+			udelay(MAC_PDMA_DELAY);
+
+		if (bytes >= 0)
+			continue;
 
 		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
-		         "%s: bus error (%d/%d)\n", __func__, transferred, len);
+		         "%s: bus error (%d/%d)\n", __func__, d - dst, len);
 		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-		d = dst + transferred;
-		n = len - transferred;
+		result = -1;
+		goto out;
 	}
 
 	scmd_printk(KERN_ERR, hostdata->connected,
 	            "%s: phase mismatch or !DRQ\n", __func__);
 	NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-	return -1;
+	result = -1;
+out:
+	if (macintosh_config->ident == MAC_MODEL_IIFX)
+		write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
+	return result;
 }
 
-
-#define CP_MEM_TO_IO(s,d,n)				\
-__asm__ __volatile__					\
-    ("    cmp.w  #4,%2\n"				\
-     "    bls    8f\n"					\
-     "    move.w %0,%%d0\n"				\
-     "    neg.b  %%d0\n"				\
-     "    and.w  #3,%%d0\n"				\
-     "    sub.w  %%d0,%2\n"				\
-     "    bra    2f\n"					\
-     " 1: move.b (%0)+,(%1)\n"				\
-     " 2: dbf    %%d0,1b\n"				\
-     "    move.w %2,%%d0\n"				\
-     "    lsr.w  #5,%%d0\n"				\
-     "    bra    4f\n"					\
-     " 3: move.l (%0)+,(%1)\n"				\
-     "31: move.l (%0)+,(%1)\n"				\
-     "32: move.l (%0)+,(%1)\n"				\
-     "33: move.l (%0)+,(%1)\n"				\
-     "34: move.l (%0)+,(%1)\n"				\
-     "35: move.l (%0)+,(%1)\n"				\
-     "36: move.l (%0)+,(%1)\n"				\
-     "37: move.l (%0)+,(%1)\n"				\
-     " 4: dbf    %%d0,3b\n"				\
-     "    move.w %2,%%d0\n"				\
-     "    lsr.w  #2,%%d0\n"				\
-     "    and.w  #7,%%d0\n"				\
-     "    bra    6f\n"					\
-     " 5: move.l (%0)+,(%1)\n"				\
-     " 6: dbf    %%d0,5b\n"				\
-     "    and.w  #3,%2\n"				\
-     "    bra    8f\n"					\
-     " 7: move.b (%0)+,(%1)\n"				\
-     " 8: dbf    %2,7b\n"				\
-     "    moveq.l #0, %2\n"				\
-     " 9: \n"						\
-     ".section .fixup,\"ax\"\n"				\
-     "    .even\n"					\
-     "91: moveq.l #1, %2\n"				\
-     "    jra 9b\n"					\
-     "94: moveq.l #4, %2\n"				\
-     "    jra 9b\n"					\
-     ".previous\n"					\
-     ".section __ex_table,\"a\"\n"			\
-     "   .align 4\n"					\
-     "   .long  1b,91b\n"				\
-     "   .long  3b,94b\n"				\
-     "   .long 31b,94b\n"				\
-     "   .long 32b,94b\n"				\
-     "   .long 33b,94b\n"				\
-     "   .long 34b,94b\n"				\
-     "   .long 35b,94b\n"				\
-     "   .long 36b,94b\n"				\
-     "   .long 37b,94b\n"				\
-     "   .long  5b,94b\n"				\
-     "   .long  7b,91b\n"				\
-     ".previous"					\
-     : "=a"(s), "=a"(d), "=d"(n)			\
-     : "0"(s), "1"(d), "2"(n)				\
-     : "d0")
-
 static inline int macscsi_pwrite(struct NCR5380_hostdata *hostdata,
                                  unsigned char *src, int len)
 {
 	unsigned char *s = src;
 	u8 __iomem *d = hostdata->pdma_io + (OUTPUT_DATA_REG << 4);
-	int n = len;
-	int transferred;
+	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, HZ / 64)) {
-		CP_MEM_TO_IO(s, d, n);
+		int bytes;
 
-		transferred = s - src - n;
-		hostdata->pdma_residual = len - transferred;
+		if (macintosh_config->ident == MAC_MODEL_IIFX)
+			write_ctrl_reg(hostdata, CTRL_HANDSHAKE_MODE |
+			                         CTRL_INTERRUPTS_ENABLE);
 
-		/* Target changed phase early? */
-		if (NCR5380_poll_politely2(hostdata, STATUS_REG, SR_REQ, SR_REQ,
-		                           BUS_AND_STATUS_REG, BASR_ACK, BASR_ACK, HZ / 64) < 0)
-			scmd_printk(KERN_ERR, hostdata->connected,
-			            "%s: !REQ and !ACK\n", __func__);
-		if (!(NCR5380_read(BUS_AND_STATUS_REG) & BASR_PHASE_MATCH))
-			return 0;
+		bytes = mac_pdma_send(s, d, min(hostdata->pdma_residual, 512));
+
+		if (bytes > 0) {
+			s += bytes;
+			hostdata->pdma_residual -= bytes;
+		}
 
-		/* No bus error. */
-		if (n == 0) {
+		if (hostdata->pdma_residual == 0) {
 			if (NCR5380_poll_politely(hostdata, TARGET_COMMAND_REG,
 			                          TCR_LAST_BYTE_SENT,
-			                          TCR_LAST_BYTE_SENT, HZ / 64) < 0)
+			                          TCR_LAST_BYTE_SENT,
+			                          HZ / 64) < 0) {
 				scmd_printk(KERN_ERR, hostdata->connected,
 				            "%s: Last Byte Sent timeout\n", __func__);
-			return 0;
+				result = -1;
+			}
+			goto out;
 		}
 
+		if (NCR5380_poll_politely2(hostdata, STATUS_REG, SR_REQ, SR_REQ,
+		                           BUS_AND_STATUS_REG, BASR_ACK,
+		                           BASR_ACK, HZ / 64) < 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)
+			continue;
+
 		dsprintk(NDEBUG_PSEUDO_DMA, hostdata->host,
-		         "%s: bus error (%d/%d)\n", __func__, transferred, len);
+		         "%s: bus error (%d/%d)\n", __func__, s - src, len);
 		NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-		s = src + transferred;
-		n = len - transferred;
+		result = -1;
+		goto out;
 	}
 
 	scmd_printk(KERN_ERR, hostdata->connected,
 	            "%s: phase mismatch or !DRQ\n", __func__);
 	NCR5380_dprint(NDEBUG_PSEUDO_DMA, hostdata->host);
-
-	return -1;
+	result = -1;
+out:
+	if (macintosh_config->ident == MAC_MODEL_IIFX)
+		write_ctrl_reg(hostdata, CTRL_INTERRUPTS_ENABLE);
+	return result;
 }
 
 static int macscsi_dma_xfer_len(struct NCR5380_hostdata *hostdata,
                                 struct scsi_cmnd *cmd)
 {
 	if (hostdata->flags & FLAG_NO_PSEUDO_DMA ||
-	    cmd->SCp.this_residual < 16)
+	    cmd->SCp.this_residual < setup_use_pdma)
 		return 0;
 
 	return cmd->SCp.this_residual;