From: Breno Rodrigues Alves <breno3011alves@gmail.com>
To: linux@armlinux.org.uk
Cc: James.Bottomley@HansenPartnership.com, mkp@kernel.org,
linux-arm-kernel@lists.infradead.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org,
Breno Rodrigues Alves <breno3011alves@gmail.com>
Subject: [PATCH v2] scsi: arm: Convert acornscsi-io.S to C
Date: Thu, 22 Oct 2026 15:52:24 -0300 [thread overview]
Message-ID: <20261022185224.60700-2-breno3011alves@gmail.com> (raw)
In-Reply-To: <20261022185224.60700-1-breno3011alves@gmail.com>
The Acorn SCSI expansion card presents each 16-bit SCSI data halfword
on the low half of a 32-bit card access. The hand-written assembly
in acornscsi-io.S implements the two directions of the data path:
- __acornscsi_in() : packs pairs of 16-bit card reads into 32-bit
memory words
- __acornscsi_out() : expands 16-bit memory halfwords into 32-bit
card writes (duplicating the halfword in both
halves for the bulk of the transfer)
Both routines are simple pointer walks that a modern compiler handles
just as well as hand-written assembly, so replace the .S file with an
equivalent C implementation.
The C version takes its arguments as (void __iomem *, char *, int),
matching the prototype actually used by acornscsi.c. The assembly
version had no C prototype, so the original comment declaring the
first argument as unsigned int was never enforced; using the caller's
type removes that latent inconsistency and lets the MMIO accessors
do the right thing on any architecture.
Note on odd transfer lengths: the original assembly dropped the final
odd byte when the tail reached the two-byte handler, leaving the byte
unwritten (out) or unread (in). The C version advances the MMIO
pointer by a full 32-bit card word in the trailing loop, so the
remaining odd byte is transferred through the low half of the next
card word, which is where the hardware actually samples it. Callers
in acornscsi.c pass even lengths in practice, so this is a latent-bug
fix, not a behaviour change that affects existing systems.
No Makefile change is required: acornscsi_mod-objs already lists
acornscsi-io.o, and the build system will pick up the new .c file in
preference to the removed .S file.
Signed-off-by: Breno Rodrigues Alves <breno3011alves@gmail.com>
---
drivers/scsi/arm/acornscsi-io.S | 135 -------------------------
drivers/scsi/arm/acornscsi-io.c | 168 ++++++++++++++++++++++++++++++++
drivers/scsi/arm/acornscsi-io.h | 14 +++
drivers/scsi/arm/acornscsi.c | 4 +-
4 files changed, 184 insertions(+), 137 deletions(-)
delete mode 100644 drivers/scsi/arm/acornscsi-io.S
create mode 100644 drivers/scsi/arm/acornscsi-io.c
create mode 100644 drivers/scsi/arm/acornscsi-io.h
diff --git a/drivers/scsi/arm/acornscsi-io.S b/drivers/scsi/arm/acornscsi-io.S
deleted file mode 100644
index fdd7237bb..000000000
--- a/drivers/scsi/arm/acornscsi-io.S
+++ /dev/null
@@ -1,135 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * linux/drivers/acorn/scsi/acornscsi-io.S: Acorn SCSI card IO
- */
-#include <linux/linkage.h>
-
-#include <asm/assembler.h>
-#include <mach/hardware.h>
-
-#if defined(__APCS_32__)
-#define LOADREGS(t,r,l...) ldm##t r, l
-#elif defined(__APCS_26__)
-#define LOADREGS(t,r,l...) ldm##t r, l##^
-#endif
-
-@ Purpose: transfer a block of data from the acorn scsi card to memory
-@ Proto : void acornscsi_in(unsigned int addr_start, char *buffer, int length)
-@ Returns: nothing
-
- .align
-ENTRY(__acornscsi_in)
- stmfd sp!, {r4 - r7, lr}
- bic r0, r0, #3
- mov lr, #0xff
- orr lr, lr, #0xff00
-acornscsi_in16lp:
- subs r2, r2, #16
- bmi acornscsi_in8
- ldmia r0!, {r3, r4, r5, r6}
- and r3, r3, lr
- orr r3, r3, r4, lsl #16
- and r4, r5, lr
- orr r4, r4, r6, lsl #16
- ldmia r0!, {r5, r6, r7, ip}
- and r5, r5, lr
- orr r5, r5, r6, lsl #16
- and r6, r7, lr
- orr r6, r6, ip, lsl #16
- stmia r1!, {r3 - r6}
- bne acornscsi_in16lp
- LOADREGS(fd, sp!, {r4 - r7, pc})
-
-acornscsi_in8: adds r2, r2, #8
- bmi acornscsi_in4
- ldmia r0!, {r3, r4, r5, r6}
- and r3, r3, lr
- orr r3, r3, r4, lsl #16
- and r4, r5, lr
- orr r4, r4, r6, lsl #16
- stmia r1!, {r3 - r4}
- LOADREGS(eqfd, sp!, {r4 - r7, pc})
- sub r2, r2, #8
-
-acornscsi_in4: adds r2, r2, #4
- bmi acornscsi_in2
- ldmia r0!, {r3, r4}
- and r3, r3, lr
- orr r3, r3, r4, lsl #16
- str r3, [r1], #4
- LOADREGS(eqfd, sp!, {r4 - r7, pc})
- sub r2, r2, #4
-
-acornscsi_in2: adds r2, r2, #2
- ldr r3, [r0], #4
- and r3, r3, lr
- strb r3, [r1], #1
- mov r3, r3, lsr #8
- strplb r3, [r1], #1
- LOADREGS(fd, sp!, {r4 - r7, pc})
-
-@ Purpose: transfer a block of data from memory to the acorn scsi card
-@ Proto : void acornscsi_in(unsigned int addr_start, char *buffer, int length)
-@ Returns: nothing
-
-ENTRY(__acornscsi_out)
- stmfd sp!, {r4 - r6, lr}
- bic r0, r0, #3
-acornscsi_out16lp:
- subs r2, r2, #16
- bmi acornscsi_out8
- ldmia r1!, {r4, r6, ip, lr}
- mov r3, r4, lsl #16
- orr r3, r3, r3, lsr #16
- mov r4, r4, lsr #16
- orr r4, r4, r4, lsl #16
- mov r5, r6, lsl #16
- orr r5, r5, r5, lsr #16
- mov r6, r6, lsr #16
- orr r6, r6, r6, lsl #16
- stmia r0!, {r3, r4, r5, r6}
- mov r3, ip, lsl #16
- orr r3, r3, r3, lsr #16
- mov r4, ip, lsr #16
- orr r4, r4, r4, lsl #16
- mov ip, lr, lsl #16
- orr ip, ip, ip, lsr #16
- mov lr, lr, lsr #16
- orr lr, lr, lr, lsl #16
- stmia r0!, {r3, r4, ip, lr}
- bne acornscsi_out16lp
- LOADREGS(fd, sp!, {r4 - r6, pc})
-
-acornscsi_out8: adds r2, r2, #8
- bmi acornscsi_out4
- ldmia r1!, {r4, r6}
- mov r3, r4, lsl #16
- orr r3, r3, r3, lsr #16
- mov r4, r4, lsr #16
- orr r4, r4, r4, lsl #16
- mov r5, r6, lsl #16
- orr r5, r5, r5, lsr #16
- mov r6, r6, lsr #16
- orr r6, r6, r6, lsl #16
- stmia r0!, {r3, r4, r5, r6}
- LOADREGS(eqfd, sp!, {r4 - r6, pc})
-
- sub r2, r2, #8
-acornscsi_out4: adds r2, r2, #4
- bmi acornscsi_out2
- ldr r4, [r1], #4
- mov r3, r4, lsl #16
- orr r3, r3, r3, lsr #16
- mov r4, r4, lsr #16
- orr r4, r4, r4, lsl #16
- stmia r0!, {r3, r4}
- LOADREGS(eqfd, sp!, {r4 - r6, pc})
-
- sub r2, r2, #4
-acornscsi_out2: adds r2, r2, #2
- ldr r3, [r1], #2
- strb r3, [r0], #1
- mov r3, r3, lsr #8
- strplb r3, [r0], #1
- LOADREGS(fd, sp!, {r4 - r6, pc})
-
diff --git a/drivers/scsi/arm/acornscsi-io.c b/drivers/scsi/arm/acornscsi-io.c
new file mode 100644
index 000000000..d882441ea
--- /dev/null
+++ b/drivers/scsi/arm/acornscsi-io.c
@@ -0,0 +1,168 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Acorn SCSI card I/O
+ *
+ * The Acorn SCSI expansion card exposes each 16-bit SCSI data
+ * halfword on the low half of a 32-bit card access:
+ *
+ * - on reads, one 16-bit value is returned per 32-bit card load;
+ * consecutive card reads are packed into 32-bit memory words
+ *
+ * - on writes, a 16-bit memory halfword is expanded into a 32-bit
+ * card word. The original assembly duplicates the halfword into
+ * both halves of the card word for the bulk of the transfer and
+ * writes only the low 16 bits of the trailing partial word,
+ * since the hardware samples only the low half.
+ */
+
+#include <linux/align.h>
+#include <linux/io.h>
+#include <linux/types.h>
+#include "acornscsi-io.h"
+
+/*
+ * Transfer a block of data from the Acorn SCSI card into memory.
+ *
+ * The card address is rounded down to a 32-bit boundary. Each
+ * 32-bit read from the card yields one valid 16-bit halfword in
+ * the low half; pairs of card reads are packed into single 32-bit
+ * memory words.
+ */
+void __acornscsi_in(void __iomem *addr, char *buffer, int length)
+{
+ const u32 __iomem *card = PTR_ALIGN_DOWN((const u32 __iomem *)addr, 4);
+ u8 *buf = (u8 *)buffer;
+
+ while (length >= 16) {
+ u32 w0 = readl(card + 0), w1 = readl(card + 1);
+ u32 w2 = readl(card + 2), w3 = readl(card + 3);
+ u32 w4 = readl(card + 4), w5 = readl(card + 5);
+ u32 w6 = readl(card + 6), w7 = readl(card + 7);
+
+ card += 8;
+
+ ((u32 *)buf)[0] = (w0 & 0xffff) | (w1 << 16);
+ ((u32 *)buf)[1] = (w2 & 0xffff) | (w3 << 16);
+ ((u32 *)buf)[2] = (w4 & 0xffff) | (w5 << 16);
+ ((u32 *)buf)[3] = (w6 & 0xffff) | (w7 << 16);
+
+ buf += 16;
+ length -= 16;
+ }
+
+ while (length >= 8) {
+ u32 w0 = readl(card + 0), w1 = readl(card + 1);
+ u32 w2 = readl(card + 2), w3 = readl(card + 3);
+
+ card += 4;
+
+ ((u32 *)buf)[0] = (w0 & 0xffff) | (w1 << 16);
+ ((u32 *)buf)[1] = (w2 & 0xffff) | (w3 << 16);
+
+ buf += 8;
+ length -= 8;
+ }
+
+ while (length >= 4) {
+ u32 w0 = readl(card + 0), w1 = readl(card + 1);
+
+ card += 2;
+
+ ((u32 *)buf)[0] = (w0 & 0xffff) | (w1 << 16);
+
+ buf += 4;
+ length -= 4;
+ }
+
+ while (length >= 2) {
+ u32 w0 = readl(card);
+
+ card++;
+
+ buf[0] = w0 & 0xff;
+ buf[1] = (w0 >> 8) & 0xff;
+
+ buf += 2;
+ length -= 2;
+ }
+
+ if (length >= 1) {
+ u32 w0 = readl(card);
+
+ buf[0] = w0 & 0xff;
+ }
+}
+
+/*
+ * Transfer a block of data from memory to the Acorn SCSI card.
+ *
+ * Each 16-bit value read from memory is expanded into a 32-bit card
+ * word, with the halfword duplicated in both halves (matching the
+ * original assembly). For the trailing partial halfword the card
+ * only samples the low 16 bits, so two byte stores are sufficient.
+ */
+void __acornscsi_out(void __iomem *addr, char *buffer, int length)
+{
+ u32 __iomem *card = PTR_ALIGN_DOWN((u32 __iomem *)addr, 4);
+ const u8 *buf = (const u8 *)buffer;
+
+ while (length >= 16) {
+ u32 v0 = ((const u32 *)buf)[0];
+ u32 v1 = ((const u32 *)buf)[1];
+ u32 v2 = ((const u32 *)buf)[2];
+ u32 v3 = ((const u32 *)buf)[3];
+
+ writel((v0 & 0xffff) | ((v0 & 0xffff) << 16), card + 0);
+ writel((v0 >> 16) | ((v0 >> 16) << 16), card + 1);
+ writel((v1 & 0xffff) | ((v1 & 0xffff) << 16), card + 2);
+ writel((v1 >> 16) | ((v1 >> 16) << 16), card + 3);
+ writel((v2 & 0xffff) | ((v2 & 0xffff) << 16), card + 4);
+ writel((v2 >> 16) | ((v2 >> 16) << 16), card + 5);
+ writel((v3 & 0xffff) | ((v3 & 0xffff) << 16), card + 6);
+ writel((v3 >> 16) | ((v3 >> 16) << 16), card + 7);
+
+ card += 8;
+ buf += 16;
+ length -= 16;
+ }
+
+ while (length >= 8) {
+ u32 v0 = ((const u32 *)buf)[0];
+ u32 v1 = ((const u32 *)buf)[1];
+
+ writel((v0 & 0xffff) | ((v0 & 0xffff) << 16), card + 0);
+ writel((v0 >> 16) | ((v0 >> 16) << 16), card + 1);
+ writel((v1 & 0xffff) | ((v1 & 0xffff) << 16), card + 2);
+ writel((v1 >> 16) | ((v1 >> 16) << 16), card + 3);
+
+ card += 4;
+ buf += 8;
+ length -= 8;
+ }
+
+ while (length >= 4) {
+ u32 v0 = ((const u32 *)buf)[0];
+
+ writel((v0 & 0xffff) | ((v0 & 0xffff) << 16), card + 0);
+ writel((v0 >> 16) | ((v0 >> 16) << 16), card + 1);
+
+ card += 2;
+ buf += 4;
+ length -= 4;
+ }
+
+ while (length >= 2) {
+ u16 v = *(const u16 *)buf;
+ void __iomem *cp = (void __iomem *)card;
+
+ writeb(v & 0xff, cp);
+ writeb(v >> 8, cp + 1);
+
+ card++;
+ buf += 2;
+ length -= 2;
+ }
+
+ if (length >= 1)
+ writeb(*buf, (void __iomem *)card);
+}
diff --git a/drivers/scsi/arm/acornscsi-io.h b/drivers/scsi/arm/acornscsi-io.h
new file mode 100644
index 000000000..64acfb8bb
--- /dev/null
+++ b/drivers/scsi/arm/acornscsi-io.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Acorn SCSI card I/O
+ */
+
+#ifndef _ACORNSCSI_IO_H
+#define _ACORNSCSI_IO_H
+
+#include <linux/io.h>
+
+void __acornscsi_in(void __iomem *addr, char *buffer, int length);
+void __acornscsi_out(void __iomem *addr, char *buffer, int length);
+
+#endif /* _ACORNSCSI_IO_H */
diff --git a/drivers/scsi/arm/acornscsi.c b/drivers/scsi/arm/acornscsi.c
index 79d7d7336..263a1bf24 100644
--- a/drivers/scsi/arm/acornscsi.c
+++ b/drivers/scsi/arm/acornscsi.c
@@ -140,6 +140,8 @@
#include <scsi/scsicam.h>
+#include "acornscsi-io.h"
+
#define VER_MAJOR 2
#define VER_MINOR 0
#define VER_PATCH 6
@@ -886,7 +888,6 @@ static
void acornscsi_data_read(AS_Host *host, char *ptr,
unsigned int start_addr, unsigned int length)
{
- extern void __acornscsi_in(void __iomem *, char *buf, int len);
unsigned int page, offset, len = length;
page = (start_addr >> 12);
@@ -931,7 +932,6 @@ static
void acornscsi_data_write(AS_Host *host, char *ptr,
unsigned int start_addr, unsigned int length)
{
- extern void __acornscsi_out(void __iomem *, char *buf, int len);
unsigned int page, offset, len = length;
page = (start_addr >> 12);
--
2.56.0
next prev parent reply other threads:[~2026-10-22 18:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-22 18:36 [PATCH 0/1] " Breno Rodrigues Alves
2026-10-22 18:36 ` [PATCH] " Breno Rodrigues Alves
2026-10-22 18:52 ` [PATCH v2 0/1] " Breno Rodrigues Alves
2026-10-22 18:52 ` Breno Rodrigues Alves [this message]
2026-10-22 19:22 ` [PATCH v2] " Bart Van Assche
2026-10-22 20:30 ` Breno Rodrigues Alves
2026-10-22 21:02 ` Breno Rodrigues Alves
2026-10-22 20:30 ` [PATCH v3] " Breno Rodrigues Alves
2026-10-22 20:49 ` Bart Van Assche
2026-10-22 21:02 ` [PATCH v4] " Breno Rodrigues Alves
2026-10-22 21:36 ` Bart Van Assche
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20261022185224.60700-2-breno3011alves@gmail.com \
--to=breno3011alves@gmail.com \
--cc=James.Bottomley@HansenPartnership.com \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=mkp@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®