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Thu, 22 Oct 2026 14:03:09 -0700 (PDT) Received: from Biostar-A520MT ([187.94.15.233]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-9910160bad4sm527066241.1.2026.10.22.14.03.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 14:03:08 -0700 (PDT) From: Breno Rodrigues Alves To: linux@armlinux.org.uk Cc: Bart Van Assche , 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 Subject: [PATCH v4] scsi: arm: Convert acornscsi-io.S to C Date: Thu, 22 Oct 2026 18:02:52 -0300 Message-ID: <20261022210252.80844-1-breno3011alves@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261022183658.58090-1-breno3011alves@gmail.com> References: <20261022183658.58090-1-breno3011alves@gmail.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. The 16-, 8- and 4-byte unrolled bodies from the assembly are folded into a single 4-byte loop per direction and expressed with put_unaligned_le32() / get_unaligned_le32(), which the compiler unrolls exactly as before. The LE variants are used because the assembly performed a plain 32-bit store on little-endian ARM, which emits bytes in little-endian order and is what the SCSI payload expects. 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 --- drivers/scsi/arm/acornscsi-io.S | 135 -------------------------------- drivers/scsi/arm/acornscsi-io.c | 105 +++++++++++++++++++++++++ drivers/scsi/arm/acornscsi-io.h | 14 ++++ drivers/scsi/arm/acornscsi.c | 4 +- 4 files changed, 121 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 - -#include -#include - -#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..08071963d --- /dev/null +++ b/drivers/scsi/arm/acornscsi-io.c @@ -0,0 +1,105 @@ +// 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 +#include +#include +#include + +#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 >= 4) { + u32 w0 = readl(card + 0); + u32 w1 = readl(card + 1); + + put_unaligned_le32((w0 & 0xffff) | (w1 << 16), buf); + + card += 2; + buf += 4; + length -= 4; + } + + if (length >= 2) { + u32 w0 = readl(card); + + put_unaligned_le16(w0 & 0xffff, buf); + + card++; + buf += 2; + length -= 2; + } + + if (length >= 1) { + u32 w0 = readl(card); + + *buf = 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 >= 4) { + u32 v = get_unaligned_le32(buf); + u32 lo = v & 0xffff; + u32 hi = v >> 16; + + writel(lo | (lo << 16), card + 0); + writel(hi | (hi << 16), card + 1); + + card += 2; + buf += 4; + length -= 4; + } + + if (length >= 2) { + void __iomem *cp = (void __iomem *)card; + + writeb(buf[0], cp); + writeb(buf[1], cp + 1); + + card++; + buf += 2; + length -= 2; + } + + if (length >= 1) + writeb(*buf, 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 + +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 +#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