next-cube: always use retval to return rtc read values

Instead of shifting out rtc read values from individual rtc registers, change
the logic so that rtc read commands are executed when the last bit of the rtc
command is received and the result stored in retval. This simplifies the rtc
read logic such that the shift out logic can be consolidated for rtc phases
between 8 and 16.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-ID: <20241222130012.1013374-22-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>

1 files changed, 40 insertions, 59 deletions

diff --git a/hw/m68k/next-cube.c b/hw/m68k/next-cube.c
index eb7d3a9..a391171 100644
--- a/hw/m68k/next-cube.c
+++ b/hw/m68k/next-cube.c
@@ -190,93 +190,74 @@ static void next_scr2_rtc_update(NeXTPC *s)
             if (rtc->phase < 8) {
                 rtc->command = (rtc->command << 1) |
                                ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
-            }
-            if (rtc->phase >= 8 && rtc->phase < 16) {
-                if (next_rtc_cmd_is_write(rtc->command)) {
-                    /* Shift in value to write */
-                    rtc->value = (rtc->value << 1) |
-                                 ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
-                } else {
-                    /* Shift out value to read */
 
-                    /* if we read RAM register, output RT_DATA bit */
-                    if (rtc->command <= 0x1F) {
-                        scr2_2 = scr2_2 & (~SCR2_RTDATA);
-                        if (rtc->ram[rtc->command] &
-                            (0x80 >> (rtc->phase - 8))) {
-                                scr2_2 |= SCR2_RTDATA;
-                        }
-
-                        rtc->retval = (rtc->retval << 1) |
-                                      ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
-                    }
-                    /* read the status 0x30 */
-                    if (rtc->command == 0x30) {
-                        scr2_2 = scr2_2 & (~SCR2_RTDATA);
-                        /* for now status = 0x98 (new rtc + FTU) */
-                        if (rtc->status & (0x80 >> (rtc->phase - 8))) {
-                            scr2_2 |= SCR2_RTDATA;
-                        }
-
-                        rtc->retval = (rtc->retval << 1) |
-                                      ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
-                    }
-                    /* read the status 0x31 */
-                    if (rtc->command == 0x31) {
-                        scr2_2 = scr2_2 & (~SCR2_RTDATA);
-                        if (rtc->control & (0x80 >> (rtc->phase - 8))) {
-                            scr2_2 |= SCR2_RTDATA;
-                        }
-                        rtc->retval = (rtc->retval << 1) |
-                                      ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
+                if (rtc->phase == 7 && !next_rtc_cmd_is_write(rtc->command)) {
+                    if (rtc->command <= 0x1f) {
+                        /* RAM registers */
+                        rtc->retval = rtc->ram[rtc->command];
                     }
-
                     if ((rtc->command >= 0x20) && (rtc->command <= 0x2F)) {
-                        scr2_2 = scr2_2 & (~SCR2_RTDATA);
-                        /* for now 0x00 */
+                        /* RTC */
                         time_t time_h = time(NULL);
                         struct tm *info = localtime(&time_h);
-                        int ret = 0;
+                        rtc->retval = 0;
 
                         switch (rtc->command) {
                         case 0x20:
-                            ret = SCR2_TOBCD(info->tm_sec);
+                            rtc->retval = SCR2_TOBCD(info->tm_sec);
                             break;
                         case 0x21:
-                            ret = SCR2_TOBCD(info->tm_min);
+                            rtc->retval = SCR2_TOBCD(info->tm_min);
                             break;
                         case 0x22:
-                            ret = SCR2_TOBCD(info->tm_hour);
+                            rtc->retval = SCR2_TOBCD(info->tm_hour);
                             break;
                         case 0x24:
-                            ret = SCR2_TOBCD(info->tm_mday);
+                            rtc->retval = SCR2_TOBCD(info->tm_mday);
                             break;
                         case 0x25:
-                            ret = SCR2_TOBCD((info->tm_mon + 1));
+                            rtc->retval = SCR2_TOBCD((info->tm_mon + 1));
                             break;
                         case 0x26:
-                            ret = SCR2_TOBCD((info->tm_year - 100));
+                            rtc->retval = SCR2_TOBCD((info->tm_year - 100));
                             break;
                         }
-
-                        if (ret & (0x80 >> (rtc->phase - 8))) {
-                            scr2_2 |= SCR2_RTDATA;
-                        }
-                        rtc->retval = (rtc->retval << 1) |
-                                      ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
+                    }
+                    if (rtc->command == 0x30) {
+                        /* read the status 0x30 */
+                        rtc->retval = rtc->status;
+                    }
+                    if (rtc->command == 0x31) {
+                        /* read the control 0x31 */
+                        rtc->retval = rtc->control;
+                    }
+                }
+            }
+            if (rtc->phase >= 8 && rtc->phase < 16) {
+                if (next_rtc_cmd_is_write(rtc->command)) {
+                    /* Shift in value to write */
+                    rtc->value = (rtc->value << 1) |
+                                 ((scr2_2 & SCR2_RTDATA) ? 1 : 0);
+                } else {
+                    /* Shift out value to read */
+                    if (rtc->retval & (0x80 >> (rtc->phase - 8))) {
+                        scr2_2 |= SCR2_RTDATA;
+                    } else {
+                        scr2_2 &= ~SCR2_RTDATA;
                     }
                 }
             }
 
             rtc->phase++;
-            if (rtc->phase == 16) {
-                if (rtc->command >= 0x80 && rtc->command <= 0x9F) {
+            if (rtc->phase == 16 && next_rtc_cmd_is_write(rtc->command)) {
+                if (rtc->command >= 0x80 && rtc->command <= 0x9f) {
+                    /* RAM registers */
                     rtc->ram[rtc->command - 0x80] = rtc->value;
                 }
-                /* write to x30 register */
-                if (rtc->command == 0xB1) {
-                    /* clear FTU */
+                if (rtc->command == 0xb1) {
+                    /* write to 0x30 register */
                     if (rtc->value & 0x04) {
+                        /* clear FTU */
                         rtc->status = rtc->status & (~0x18);
                         qemu_irq_lower(s->rtc_power_irq);
                     }