esp.c: update esp_do_dma() bypass if async_len is zero to include non-zero transfer check

In the PDMA case the last transfer from the device to the FIFO has occurred
(async_len is zero) but esp_do_dma() is still being called to drain the
remaining FIFO contents.

The additional non-zero transfer check ensures that we still defer the SCSI
layer in the case where we are waiting for data for a TI command or a DMA
enable signal.

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: <20240112125420.514425-35-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

1 files changed, 1 insertions, 1 deletions

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 14284ef..9647be4 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -696,7 +696,7 @@ static void esp_do_dma(ESPState *s)
     if (!s->current_req) {
         return;
     }
-    if (s->async_len == 0) {
+    if (s->async_len == 0 && esp_get_tc(s) && s->ti_size) {
         /* Defer until data is available.  */
         return;
     }