esp.c: remove unneeded ti_cmd field

According to the datasheet the previous ESP command remains in the ESP_CMD
register, which caused a problem when consecutive TI commands were issued as
it becomes impossible for the state machine to know when the first TI
command finishes.

This was the original reason for introducing the ti_cmd field which kept
track of the last written command for this purpose. However closer reading
of the datasheet shows that a TI command that terminates due to a change of
SCSI target phase resets the ESP_CMD register to zero which solves this
problem.

Now that this has been fixed in the previous commit, remove the unneeded
ti_cmd field and access the ESP_CMD register directly instead. Bump the
vmstate_esp version to indicate that the ti_cmd field is no longer included.

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: <20240112125420.514425-64-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>

hw/scsi/esp.c

@@ -321,7 +321,6 @@ static void do_command_phase(ESPState *s)
     fifo8_reset(&s->cmdfifo);
     s->data_ready = false;
     if (datalen != 0) {
-        s->ti_cmd = 0;
         /*
          * Switch to DATA phase but wait until initial data xfer is
          * complete before raising the command completion interrupt
@@ -908,12 +907,12 @@ void esp_transfer_data(SCSIRequest *req, uint32_t len)
      * async data transfer is delayed then s->dma is set incorrectly.
      */
 
-    if (s->ti_cmd == (CMD_TI | CMD_DMA)) {
+    if (s->rregs[ESP_CMD] == (CMD_TI | CMD_DMA)) {
         /* When the SCSI layer returns more data, raise deferred INTR_BS */
         esp_dma_ti_check(s);
 
         esp_do_dma(s);
-    } else if (s->ti_cmd == CMD_TI) {
+    } else if (s->rregs[ESP_CMD] == CMD_TI) {
         esp_do_nodma(s);
     }
 }
@@ -927,7 +926,6 @@ static void handle_ti(ESPState *s)
         return;
     }
 
-    s->ti_cmd = s->rregs[ESP_CMD];
     if (s->dma) {
         dmalen = esp_get_tc(s);
         trace_esp_handle_ti(dmalen);
@@ -1200,6 +1198,14 @@ static bool esp_is_version_6(void *opaque, int version_id)
     return version_id >= 6;
 }
 
+static bool esp_is_between_version_5_and_6(void *opaque, int version_id)
+{
+    ESPState *s = ESP(opaque);
+
+    version_id = MIN(version_id, s->mig_version_id);
+    return version_id >= 5 && version_id <= 6;
+}
+
 int esp_pre_save(void *opaque)
 {
     ESPState *s = ESP(object_resolve_path_component(
@@ -1237,7 +1243,7 @@ static int esp_post_load(void *opaque, int version_id)
 
 const VMStateDescription vmstate_esp = {
     .name = "esp",
-    .version_id = 6,
+    .version_id = 7,
     .minimum_version_id = 3,
     .post_load = esp_post_load,
     .fields = (const VMStateField[]) {
@@ -1265,7 +1271,8 @@ const VMStateDescription vmstate_esp = {
         VMSTATE_UINT8_TEST(cmdfifo_cdb_offset, ESPState, esp_is_version_5),
         VMSTATE_FIFO8_TEST(fifo, ESPState, esp_is_version_5),
         VMSTATE_FIFO8_TEST(cmdfifo, ESPState, esp_is_version_5),
-        VMSTATE_UINT8_TEST(ti_cmd, ESPState, esp_is_version_5),
+        VMSTATE_UINT8_TEST(mig_ti_cmd, ESPState,
+                           esp_is_between_version_5_and_6),
         VMSTATE_UINT8_TEST(lun, ESPState, esp_is_version_6),
         VMSTATE_END_OF_LIST()
     },

include/hw/scsi/esp.h

@@ -41,7 +41,6 @@ struct ESPState {
     uint32_t do_cmd;
 
     bool data_ready;
-    uint8_t ti_cmd;
     int dma_enabled;
 
     uint32_t async_len;
@@ -62,6 +61,8 @@ struct ESPState {
     uint8_t mig_ti_buf[ESP_FIFO_SZ];
     uint8_t mig_cmdbuf[ESP_CMDFIFO_SZ];
     uint32_t mig_cmdlen;
+
+    uint8_t mig_ti_cmd;
 };
 
 #define TYPE_SYSBUS_ESP "sysbus-esp"