esp: apply transfer length adjustment when STC is zero at TC load time

Perform the length adjustment whereby a value of 0 in the STC represents
a transfer length of 0x10000 at the point where the TC is loaded at the
start of a DMA command rather than just when a TI (Transfer Information)
command is executed. This better matches the description as given in the
datasheet.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20210304221103.6369-12-mark.cave-ayland@ilande.co.uk>

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 125bdea32aed8c606160307a0515430b26dbef20..349067eb6a6b7fbe341aa88788b41515e255c505 100644 (file)
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -561,9 +561,6 @@ static void handle_ti(ESPState *s)
     }
 
     dmalen = esp_get_tc(s);
-    if (dmalen == 0) {
-        dmalen = 0x10000;
-    }
     s->dma_counter = dmalen;
 
     if (s->do_cmd) {
@@ -698,7 +695,11 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val)
         if (val & CMD_DMA) {
             s->dma = 1;
             /* Reload DMA counter.  */
-            esp_set_tc(s, esp_get_stc(s));
+            if (esp_get_stc(s) == 0) {
+                esp_set_tc(s, 0x10000);
+            } else {
+                esp_set_tc(s, esp_get_stc(s));
+            }
         } else {
             s->dma = 0;
         }