esp.c: remove restriction on FIFO read access when DMA memory routine…

…s defined

The latest state machines can handle mixing DMA and non-DMA FIFO access for all
SCSI phases except DATA IN and DATA OUT. For DATA IN and DATA OUT phases, the
transfer is complete when TC == 0 and the updated logic will now handle TC
underflow correctly, which makes it just about impossible to manually manipulate
the FIFO during a DMA transfer.

Remove the restriction on FIFO read access when DMA memory routines are defined
which also allows the NeXTCube machine to pass its self-test.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Tested-by: Helge Deller <deller@gmx.de>
Tested-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20240112125420.514425-74-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

hw/scsi/esp.c

@@ -1133,14 +1133,7 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr)
 
     switch (saddr) {
     case ESP_FIFO:
-        if (s->dma_memory_read && s->dma_memory_write &&
-                (s->rregs[ESP_RSTAT] & STAT_PIO_MASK) == 0) {
-            /* Data out.  */
-            qemu_log_mask(LOG_UNIMP, "esp: PIO data read not implemented\n");
-            s->rregs[ESP_FIFO] = 0;
-        } else {
-            s->rregs[ESP_FIFO] = esp_fifo_pop(&s->fifo);
-        }
+        s->rregs[ESP_FIFO] = esp_fifo_pop(&s->fifo);
         val = s->rregs[ESP_FIFO];
         break;
     case ESP_RINTR: