[PATCH 86/88] esp.c: keep track of the DRQ state during DMA

[Mark Cave-Ayland]

Currently the DRQ IRQ is updated every time DMA data is sent/received which
is both inefficient and causes excessive logging of the DRQ state. Add a
new drq_state bool that only updates the DRQ IRQ if its state changes.

This commit adds the new drq_state bool to the migration state: since the
version number has already been increased earlier in the series, there is
no need to repeat it again here. The DRQ IRQ is (currently) only used for
PDMA transfers which already have a migration break in this series so
there are no problems setting its value post-load.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
---
 hw/scsi/esp.c         | 15 +++++++++++----
 include/hw/scsi/esp.h |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
index fb68606f00..04615d8b5f 100644
--- a/hw/scsi/esp.c
+++ b/hw/scsi/esp.c
@@ -62,14 +62,20 @@ static void esp_lower_irq(ESPState *s)
 
 static void esp_raise_drq(ESPState *s)
 {
-    qemu_irq_raise(s->drq_irq);
-    trace_esp_raise_drq();
+    if (!(s->drq_state)) {
+        qemu_irq_raise(s->drq_irq);
+        trace_esp_raise_drq();
+        s->drq_state = true;
+    }
 }
 
 static void esp_lower_drq(ESPState *s)
 {
-    qemu_irq_lower(s->drq_irq);
-    trace_esp_lower_drq();
+    if (s->drq_state) {
+        qemu_irq_lower(s->drq_irq);
+        trace_esp_lower_drq();
+        s->drq_state = false;
+    }
 }
 
 void esp_dma_enable(ESPState *s, int irq, int level)
@@ -1358,6 +1364,7 @@ const VMStateDescription vmstate_esp = {
         VMSTATE_UINT8_TEST(mig_ti_cmd, ESPState,
                            esp_is_between_version_5_and_6),
         VMSTATE_UINT8_TEST(lun, ESPState, esp_is_version_6),
+        VMSTATE_BOOL(drq_state, ESPState),
         VMSTATE_END_OF_LIST()
     },
 };
diff --git a/include/hw/scsi/esp.h b/include/hw/scsi/esp.h
index c6e8b64e20..533d856aa3 100644
--- a/include/hw/scsi/esp.h
+++ b/include/hw/scsi/esp.h
@@ -26,6 +26,7 @@ struct ESPState {
     uint8_t wregs[ESP_REGS];
     qemu_irq irq;
     qemu_irq drq_irq;
+    bool drq_state;
     uint8_t chip_id;
     bool tchi_written;
     int32_t ti_size;
-- 
2.39.2