hw/sd/sdhci: Resume pending DMA transfers on MMIO accesses

If we have pending DMA requests scheduled, process them first.
So far we don't need to implement a bottom half to process them.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Alexander Bulekov <alxndr@bu.edu>
Message-Id: <20200903172806.489710-3-f4bug@amsat.org>

hw/sd/sdhci.c

@@ -948,11 +948,21 @@ sdhci_buff_access_is_sequential(SDHCIState *s, unsigned byte_num)
     return true;
 }
 
+static void sdhci_resume_pending_transfer(SDHCIState *s)
+{
+    timer_del(s->transfer_timer);
+    sdhci_data_transfer(s);
+}
+
 static uint64_t sdhci_read(void *opaque, hwaddr offset, unsigned size)
 {
     SDHCIState *s = (SDHCIState *)opaque;
     uint32_t ret = 0;
 
+    if (timer_pending(s->transfer_timer)) {
+        sdhci_resume_pending_transfer(s);
+    }
+
     switch (offset & ~0x3) {
     case SDHC_SYSAD:
         ret = s->sdmasysad;
@@ -1096,6 +1106,10 @@ sdhci_write(void *opaque, hwaddr offset, uint64_t val, unsigned size)
     uint32_t value = val;
     value <<= shift;
 
+    if (timer_pending(s->transfer_timer)) {
+        sdhci_resume_pending_transfer(s);
+    }
+
     switch (offset & ~0x3) {
     case SDHC_SYSAD:
         s->sdmasysad = (s->sdmasysad & mask) | value;