From 7544b3834b1b6c195d974185ad59dd2d17dd8073 Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Fri, 17 Apr 2020 19:10:22 -0400
Subject: [PATCH] emul/hw/rc2014: implement blkread in sdc

I now get to "fls" in recipes/rc2014/sdcard!
---
 emul/hw/rc2014/classic.c | 11 +++++++++--
 emul/hw/rc2014/sdc.c     | 45 ++++++++++++++++++++++++++++++++++++++++++---
 emul/hw/rc2014/sdc.h     |  6 ++++++
 3 files changed, 57 insertions(+), 5 deletions(-)

diff --git a/emul/hw/rc2014/classic.c b/emul/hw/rc2014/classic.c
index 1791dfd..f04003d 100644
--- a/emul/hw/rc2014/classic.c
+++ b/emul/hw/rc2014/classic.c
@@ -68,8 +68,8 @@ static void iowr_sdc_cslow(uint8_t val)
 
 int main(int argc, char *argv[])
 {
-    if (argc != 2) {
-        fprintf(stderr, "Usage: ./classic /path/to/rom\n");
+    if (argc < 2) {
+        fprintf(stderr, "Usage: ./classic /path/to/rom [sdcard.img]\n");
         return 1;
     }
     FILE *fp = fopen(argv[1], "r");
@@ -107,6 +107,10 @@ int main(int argc, char *argv[])
 
     acia_init(&acia);
     sdc_init(&sdc);
+    if (argc == 3) {
+        fprintf(stderr, "Setting up SD card image\n");
+        sdc.fp = fopen(argv[2], "r+");
+    }
     m->iord[ACIA_CTL_PORT] = iord_acia_ctl;
     m->iord[ACIA_DATA_PORT] = iord_acia_data;
     m->iowr[ACIA_CTL_PORT] = iowr_acia_ctl;
@@ -152,5 +156,8 @@ int main(int argc, char *argv[])
         tcsetattr(0, TCSADRAIN, &saved_term);
         emul_printdebug();
     }
+    if (sdc.fp) {
+        fclose(sdc.fp);
+    }
     return 0;
 }
diff --git a/emul/hw/rc2014/sdc.c b/emul/hw/rc2014/sdc.c
index f863038..9560698 100644
--- a/emul/hw/rc2014/sdc.c
+++ b/emul/hw/rc2014/sdc.c
@@ -1,6 +1,16 @@
 #include <stdio.h>
 #include "sdc.h"
 
+// Add data to crc with polynomial 0x1021
+// https://stackoverflow.com/a/23726131
+static uint16_t crc16(uint16_t crc, uint8_t data)
+{
+    uint8_t x = crc >> 8 ^ data;
+    x ^= x>>4;
+    crc = (crc << 8) ^ ((uint16_t)(x << 12)) ^ ((uint16_t)(x <<5)) ^ ((uint16_t)x);
+    return crc;
+}
+
 void sdc_init(SDC *sdc)
 {
     sdc->selected = false;
@@ -8,6 +18,8 @@ void sdc_init(SDC *sdc)
     sdc->recvidx = 0;
     sdc->sendidx = -1;
     sdc->resp = 0xff;
+    sdc->fp = NULL;
+    sdc->cmd17bytes = -1;
 }
 
 void sdc_cslow(SDC *sdc)
@@ -38,6 +50,20 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         }
         return;
     }
+    if (sdc->cmd17bytes >= 0) {
+        if (sdc->fp) {
+            sdc->resp = getc(sdc->fp);
+        }
+        sdc->crc16 = crc16(sdc->crc16, sdc->resp);
+        sdc->cmd17bytes++;
+        if (sdc->cmd17bytes == 512) {
+            sdc->sendbuf[3] = sdc->crc16 >> 8;
+            sdc->sendbuf[4] = sdc->crc16 & 0xff;
+            sdc->sendidx = 3;
+            sdc->cmd17bytes = -1;
+        }
+        return;
+    }
     if ((sdc->recvidx == 0) && ((val > 0x7f) || (val < 0x40))) {
         // not a command
         return;
@@ -51,8 +77,9 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
     val &= 0x3f;
     sdc->recvidx = 0;
     uint8_t *b = sdc->recvbuf;
-    fprintf(stderr, "cmd %02x %02x %02x %02x %02x\n", b[0], b[1], b[2], b[3], b[4]);
     uint8_t cmd = b[0] & 0x3f;
+    uint16_t arg1 = (b[1] << 8) | b[2];
+    uint16_t arg2 = (b[3] << 8) | b[4];
     if (sdc->initstat == 8) {
         // At this stage, we're expecting CMD0
         if (cmd == 0) {
@@ -64,7 +91,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
     }
     if (sdc->initstat == 9) {
         // At this stage, we're expecting CMD8 with 0x1aa arg2
-        if ((cmd == 8) && (b[3] == 0x01) && (b[4] == 0xaa)) {
+        if ((cmd == 8) && (arg2 == 0x01aa)) {
             sdc->initstat++;
             sdc->sendbuf[0] = 0x01;
             sdc->sendbuf[1] = 0;
@@ -90,7 +117,7 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
     }
     if (sdc->initstat == 11) {
         // At this stage, we're expecting CMD41
-        if ((cmd == 41) && (b[1] == 0x40) && (b[2] == 0x00)) {
+        if ((cmd == 41) && (arg1 == 0x4000)) {
             sdc->initstat++;
             sdc->sendbuf[4] = 0x00;
             sdc->sendidx = 4;
@@ -100,6 +127,18 @@ void sdc_spi_wr(SDC *sdc, uint8_t val)
         return;
     }
     // We have a fully initialized card.
+    if (cmd == 17) {
+        if (sdc->fp) {
+            fseek(sdc->fp, arg2*512, SEEK_SET);
+        }
+        sdc->sendbuf[3] = 0x00;
+        // data token
+        sdc->sendbuf[4] = 0xfe;
+        sdc->sendidx = 3;
+        sdc->cmd17bytes = 0;
+        sdc->crc16 = 0;
+        return;
+    }
     // Simulate success for any unknown command.
     sdc->sendbuf[4] = 0x00;
     sdc->sendidx = 4;
diff --git a/emul/hw/rc2014/sdc.h b/emul/hw/rc2014/sdc.h
index 22748cd..0d5aa19 100644
--- a/emul/hw/rc2014/sdc.h
+++ b/emul/hw/rc2014/sdc.h
@@ -19,6 +19,12 @@ typedef struct {
     // One byte response. When all other response buffers are empty, return
     // this.
     uint8_t resp;
+    // File used for contents read/write
+    FILE *fp;
+    // number of bytes read into the current CMD17. -1 means no CMD17 active.
+    int cmd17bytes;
+    // running crc16 during read and write operations.
+    uint16_t crc16;
 } SDC;
 
 void sdc_init(SDC *sdc);