The contents of the FIFO should only be copied to cmdfifo for ESP commands that
are sending data to the SCSI bus, which are the SEL_* commands and the TI
command. Otherwise any incoming data should be held in the FIFO as normal.

This fixes booting of really old 32-bit SPARC Linux kernels such as Aurelien's
debian_etch_sparc_small.qcow2 test image.

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: <20240112125420.514425-77-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/esp.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index ca26415d5f..17e2db442c 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -757,13 +757,13 @@ static void esp_do_nodma(ESPState *s)
         break;
 
     case STAT_CD:
-        /* Copy FIFO into cmdfifo */
-        n = esp_fifo_pop_buf(&s->fifo, buf, fifo8_num_used(&s->fifo));
-        n = MIN(fifo8_num_free(&s->cmdfifo), n);
-        fifo8_push_all(&s->cmdfifo, buf, n);
-
         switch (s->rregs[ESP_CMD]) {
         case CMD_TI:
+            /* Copy FIFO into cmdfifo */
+            n = esp_fifo_pop_buf(&s->fifo, buf, fifo8_num_used(&s->fifo));
+            n = MIN(fifo8_num_free(&s->cmdfifo), n);
+            fifo8_push_all(&s->cmdfifo, buf, n);
+
             cmdlen = fifo8_num_used(&s->cmdfifo);
             trace_esp_handle_ti_cmd(cmdlen);
 
@@ -788,6 +788,11 @@ static void esp_do_nodma(ESPState *s)
 
         case CMD_SEL | CMD_DMA:
         case CMD_SELATN | CMD_DMA:
+            /* Copy FIFO into cmdfifo */
+            n = esp_fifo_pop_buf(&s->fifo, buf, fifo8_num_used(&s->fifo));
+            n = MIN(fifo8_num_free(&s->cmdfifo), n);
+            fifo8_push_all(&s->cmdfifo, buf, n);
+
             /* Handle when DMA transfer is terminated by non-DMA FIFO write */
             if (esp_cdb_length(s) && esp_cdb_length(s) ==
                 fifo8_num_used(&s->cmdfifo) - s->cmdfifo_cdb_offset) {
@@ -798,7 +803,11 @@ static void esp_do_nodma(ESPState *s)
 
         case CMD_SEL:
         case CMD_SELATN:
-            /* FIFO already contain entire CDB */
+            /* FIFO already contain entire CDB: copy to cmdfifo and execute */
+            n = esp_fifo_pop_buf(&s->fifo, buf, fifo8_num_used(&s->fifo));
+            n = MIN(fifo8_num_free(&s->cmdfifo), n);
+            fifo8_push_all(&s->cmdfifo, buf, n);
+
             do_cmd(s);
             break;
         }
-- 
2.39.2