[Qemu-devel] [PATCH v3] esp: Do not overwrite ESP_TCHI after reset

[Paolo Bonzini <pbonzini@redhat.com>]

From: Hannes Reinecke <hare@suse.de>

After a reset ESP_TCHI should contain the unique ID
of the chip. This value will be overwritten with the
current tranfer count if the transfer count has
previously been set.
So we should always return the chip id if ESP_TCHI
has never been written to.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/scsi/esp.c         | 11 +++++++++--
 include/hw/scsi/esp.h |  1 +
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index 5ab44d8..272d13d 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -364,7 +364,7 @@ void esp_hard_reset(ESPState *s)
 {
     memset(s->rregs, 0, ESP_REGS);
     memset(s->wregs, 0, ESP_REGS);
-    s->rregs[ESP_TCHI] = s->chip_id;
+    s->tchi_written = 0;
     s->ti_size = 0;
     s->ti_rptr = 0;
     s->ti_wptr = 0;
@@ -422,6 +422,11 @@ uint64_t esp_reg_read(ESPState *s, uint32_t saddr)
         esp_lower_irq(s);
 
         return old_val;
+    case ESP_TCHI:
+        /* Return the unique id if the value has never been written */
+        if (!s->tchi_written) {
+            return s->chip_id;
+        }
     default:
         break;
     }
@@ -432,9 +437,11 @@ void esp_reg_write(ESPState *s, uint32_t saddr, uint64_t val)
 {
     trace_esp_mem_writeb(saddr, s->wregs[saddr], val);
     switch (saddr) {
+    case ESP_TCHI:
+        s->tchi_written = true;
+        /* fall through */
     case ESP_TCLO:
     case ESP_TCMID:
-    case ESP_TCHI:
         s->rregs[ESP_RSTAT] &= ~STAT_TC;
         break;
     case ESP_FIFO:
diff --git a/include/hw/scsi/esp.h b/include/hw/scsi/esp.h
index e079fb8..6c79527 100644
--- a/include/hw/scsi/esp.h
+++ b/include/hw/scsi/esp.h
@@ -22,6 +22,7 @@ struct ESPState {
     uint8_t wregs[ESP_REGS];
     qemu_irq irq;
     uint8_t chip_id;
+    bool tchi_written;
     int32_t ti_size;
     uint32_t ti_rptr, ti_wptr;
     uint32_t status;
-- 
1.8.3.1