Add driver that uses the SD card on SF2000

The current SF2000 firmware doesn't have a FIFO for communicating with
the SD card. This limits the achieved performance. This is expected to
change soon.

.gitignore

@@ -1 +1,2 @@
 .vscode
+rp2040/build

examples/spisd/build-sf2000.sh

@@ -0,0 +1,2 @@
+set -x
+vc +aos68k -I$NDK32/Include_H romtag.c version.c device.c sd.c timer.c ../../spi-lib-sf2000/spi.c ../../spi-lib-sf2000/interrupt.asm -I../../spi-lib-sf2000 -O2 -nostdlib -lamiga -o spisd.device

examples/spisd/build.sh

@@ -0,0 +1,2 @@
+set -x
+vc +aos68k -I$NDK32/Include_H romtag.c version.c device.c sd.c timer.c ../../spi-lib/spi.c ../../spi-lib/spi_low.asm -I../../spi-lib -O2 -nostdlib -lamiga -o spisd.device

spi-lib-sf2000/README.md

@@ -0,0 +1,9 @@
+# spi-lib-sf2000
+
+The [SF2000](https://github.com/jbilander/SF2000/) Amiga accelerator has an SD
+card connector whose pins are routed to its FPGA. The firmware for the FPGA
+contains a basic SPI controller, which is used to communicate with the SD card.
+This spi-lib-sf2000 library abstracts the SPI controller using the same API
+as the spi-lib for the Amiga Parallel Port to SPI Adapter. This way, the
+spisd.device driver can be compiled with the spi-lib-sf2000 to build a driver
+that works with an SD card connected to the SF2000.

spi-lib-sf2000/interrupt.asm

@@ -0,0 +1,25 @@
+    XDEF    _InterruptServer
+    CODE
+
+;struct InterruptData
+;{
+;    struct SF2000SDRegisters *regs;
+;    void (*change_isr)();
+;};
+
+    ; a1 points to InterruptData structure
+
+_InterruptServer:
+    move.l  (a1),a0
+
+    tst     14(a0)      ; check int_act
+    beq.b   .no_irq
+
+    move    #0,12(a0)   ; disable interrupt
+
+    move.l  4(a1),a1
+    jsr     (a1)
+
+.no_irq:
+    moveq   #0,d0
+    rts

spi-lib-sf2000/spi.c

@@ -0,0 +1,127 @@
+/*
+ * Written in the end of April 2020 by Niklas Ekström.
+ * Updated in July 2021 by Niklas Ekström to handle Card Present signal.
+ * Adapted in March 2025 by Niklas Ekström to work with SF2000 SD card slot.
+ */
+#include <exec/types.h>
+#include <exec/interrupts.h>
+#include <exec/libraries.h>
+
+#include <hardware/intbits.h>
+
+#include <proto/exec.h>
+
+#include "spi.h"
+
+static const char spi_lib_name[] = "spi-lib-sf2000";
+
+struct SF2000SDRegisters
+{
+    volatile UWORD clock_divisor;
+    volatile UWORD slave_select;
+    volatile UWORD card_detect;
+    volatile UWORD shift_active;
+    volatile UWORD shift_reg;
+    volatile UWORD int_req;
+    volatile UWORD int_ena;
+    volatile UWORD int_act;
+};
+
+static struct SF2000SDRegisters *regs;
+
+#define CLK_DIV_16M     2
+#define CLK_DIV_400K    124
+
+#define IRQ_CD_CHANGED  1
+
+struct InterruptData
+{
+    struct SF2000SDRegisters *regs;
+    void (*change_isr)();
+};
+
+extern void InterruptServer();
+
+struct InterruptData interrupt_data;
+struct Interrupt ports_interrupt;
+
+void spi_select()
+{
+    regs->slave_select = 1;
+}
+
+void spi_deselect()
+{
+    regs->slave_select = 0;
+}
+
+int spi_get_card_present()
+{
+    int present = regs->card_detect;
+
+    // Clear the CD changed interrupt.
+    regs->int_req = IRQ_CD_CHANGED;
+
+    // Re-enable the CD changed interrupt.
+    regs->int_ena = IRQ_CD_CHANGED;
+
+    return present;
+}
+
+void spi_set_speed(long speed)
+{
+    regs->clock_divisor = speed == SPI_SPEED_FAST ? CLK_DIV_16M : CLK_DIV_400K;
+}
+
+void spi_read(__reg("a0") UBYTE *buf, __reg("d0") ULONG size)
+{
+    for (int i = size - 1; i >= 0; i--)
+    {
+        regs->shift_reg = 0xff;
+        while (regs->shift_active) {
+        }
+        *buf++ = (UBYTE)(regs->shift_reg);
+    }
+}
+
+void spi_write(__reg("a0") const UBYTE *buf, __reg("d0") ULONG size)
+{
+    for (int i = size - 1; i >= 0; i--)
+    {
+        regs->shift_reg = *buf++;
+        while (regs->shift_active) {
+        }
+    }
+}
+
+int spi_initialize(void (*change_isr)())
+{
+    // TODO: This address should not be hardcoded,
+    // and should be read from autoconfig/expansion.library.
+    regs = (struct SF2000SDRegisters *)0xEE0000;
+
+    regs->clock_divisor = CLK_DIV_400K;
+
+    regs->int_ena = 0;
+    regs->int_req = IRQ_CD_CHANGED;
+
+    interrupt_data.regs = regs;
+    interrupt_data.change_isr = change_isr;
+
+    ports_interrupt.is_Node.ln_Type = NT_INTERRUPT;
+    ports_interrupt.is_Node.ln_Pri = -60;
+    ports_interrupt.is_Node.ln_Name = (char *)spi_lib_name;
+    ports_interrupt.is_Data = (APTR)&interrupt_data;
+    ports_interrupt.is_Code = InterruptServer;
+
+    AddIntServer(INTB_PORTS, &ports_interrupt);
+
+    return spi_get_card_present();
+}
+
+void spi_shutdown()
+{
+    regs->int_ena = 0;
+    regs->int_req = IRQ_CD_CHANGED;
+    RemIntServer(INTB_PORTS, &ports_interrupt);
+}

spi-lib-sf2000/spi.h

@@ -0,0 +1,21 @@
+/*
+ * Written in the end of April 2020 by Niklas Ekström.
+ * Updated in July 2021 by Niklas Ekström to handle Card Present signal.
+ * Adapted in March 2025 by Niklas Ekström to work with SF2000 SD card slot.
+ */
+#ifndef SPI_H_
+#define SPI_H_
+
+#define SPI_SPEED_SLOW 0
+#define SPI_SPEED_FAST 1
+
+int spi_initialize(void (*change_isr)());
+int spi_get_card_present();
+void spi_shutdown();
+void spi_set_speed(long speed);
+void spi_select();
+void spi_deselect();
+void spi_read(__reg("a0") unsigned char *buf, __reg("d0") unsigned long size);
+void spi_write(__reg("a0") const unsigned char *buf, __reg("d0") unsigned long size);
+
+#endif