[PATCH v2 13/16] esp.c: introduce esp_update_drq() and update esp_fifo_{push, pop}_buf() to use it

[Mark Cave-Ayland]

This new function sets the DRQ line correctly according to the current transfer
mode, direction and FIFO contents. Update esp_fifo_push_buf() and 
esp_fifo_pop_buf()
to use it so that DRQ is always set correctly when reading/writing multiple 
bytes
to/from the FIFO.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/esp.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 86145256ea..53a1c7ceaf 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -124,6 +124,48 @@ void esp_request_cancelled(SCSIRequest *req)
     }
 }
 
+static void esp_update_drq(ESPState *s)
+{
+    bool to_device;
+
+    switch (esp_get_phase(s)) {
+    case STAT_MO:
+    case STAT_CD:
+    case STAT_DO:
+        to_device = true;
+        break;
+
+    case STAT_DI:
+    case STAT_ST:
+    case STAT_MI:
+        to_device = false;
+        break;
+
+    default:
+        return;
+    }
+
+    if (s->dma) {
+        /* DMA request so update DRQ according to transfer direction */
+        if (to_device) {
+            if (fifo8_num_free(&s->fifo) < 2) {
+                esp_lower_drq(s);
+            } else {
+                esp_raise_drq(s);
+            }
+        } else {
+            if (fifo8_num_used(&s->fifo) < 2) {
+                esp_lower_drq(s);
+            } else {
+                esp_raise_drq(s);
+            }
+        }
+    } else {
+        /* Not a DMA request */
+        esp_lower_drq(s);
+    }
+}
+
 static void esp_fifo_push(ESPState *s, uint8_t val)
 {
     if (fifo8_num_used(&s->fifo) == s->fifo.capacity) {
@@ -137,6 +179,7 @@ static void esp_fifo_push(ESPState *s, uint8_t val)
 static void esp_fifo_push_buf(ESPState *s, uint8_t *buf, int len)
 {
     fifo8_push_all(&s->fifo, buf, len);
+    esp_update_drq(s);
 }
 
 static uint8_t esp_fifo_pop(ESPState *s)
@@ -155,6 +198,7 @@ static uint32_t esp_fifo_pop_buf(ESPState *s, uint8_t 
*dest, int maxlen)
     int len;
 
     if (maxlen == 0) {
+        esp_update_drq(s);
         return 0;
     }
 
@@ -175,6 +219,7 @@ static uint32_t esp_fifo_pop_buf(ESPState *s, uint8_t 
*dest, int maxlen)
         n += n2;
     }
 
+    esp_update_drq(s);
     return n;
 }
 
-- 
2.39.2