[PATCH v3] fdc/i8257: implement verify transfer mode

[Sven Schnelle <svens@stackframe.org>]

While working on the Tulip driver i tried to write some Teledisk images to
a floppy image which didn't work. Turned out that Teledisk checks the written
data by issuing a READ command to the FDC but running the DMA controller
in VERIFY mode. As we ignored the DMA request in that case, the DMA transfer
never finished, and Teledisk reported an error.

The i8257 spec says about verify transfers:

3) DMA verify, which does not actually involve the transfer of data. When an
8257 channel is in the DMA verify mode, it will respond the same as described
for transfer operations, except that no memory or I/O read/write control signals
will be generated.

Hervé proposed to remove all the dma_mode_ok stuff from fdc to have a more
clear boundary between DMA and FDC, so this patch also does that.

Suggested-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Sven Schnelle <svens@stackframe.org>
---
 hw/block/fdc.c       | 61 +++++++++++++-------------------------------
 hw/dma/i8257.c       | 20 ++++++++++-----
 include/hw/isa/isa.h |  1 -
 3 files changed, 31 insertions(+), 51 deletions(-)

diff --git a/hw/block/fdc.c b/hw/block/fdc.c
index ac5d31e8c1..01812c7553 100644
--- a/hw/block/fdc.c
+++ b/hw/block/fdc.c
@@ -1714,53 +1714,28 @@ static void fdctrl_start_transfer(FDCtrl *fdctrl, int direction)
     }
     fdctrl->eot = fdctrl->fifo[6];
     if (fdctrl->dor & FD_DOR_DMAEN) {
-        IsaDmaTransferMode dma_mode;
+        /* DMA transfer is enabled. */
         IsaDmaClass *k = ISADMA_GET_CLASS(fdctrl->dma);
-        bool dma_mode_ok;
-        /* DMA transfer are enabled. Check if DMA channel is well programmed */
-        dma_mode = k->get_transfer_mode(fdctrl->dma, fdctrl->dma_chann);
-        FLOPPY_DPRINTF("dma_mode=%d direction=%d (%d - %d)\n",
-                       dma_mode, direction,
-                       (128 << fdctrl->fifo[5]) *
+
+        FLOPPY_DPRINTF("direction=%d (%d - %d)\n",
+                       direction, (128 << fdctrl->fifo[5]) *
                        (cur_drv->last_sect - ks + 1), fdctrl->data_len);
-        switch (direction) {
-        case FD_DIR_SCANE:
-        case FD_DIR_SCANL:
-        case FD_DIR_SCANH:
-            dma_mode_ok = (dma_mode == ISADMA_TRANSFER_VERIFY);
-            break;
-        case FD_DIR_WRITE:
-            dma_mode_ok = (dma_mode == ISADMA_TRANSFER_WRITE);
-            break;
-        case FD_DIR_READ:
-            dma_mode_ok = (dma_mode == ISADMA_TRANSFER_READ);
-            break;
-        case FD_DIR_VERIFY:
-            dma_mode_ok = true;
-            break;
-        default:
-            dma_mode_ok = false;
-            break;
-        }
-        if (dma_mode_ok) {
-            /* No access is allowed until DMA transfer has completed */
-            fdctrl->msr &= ~FD_MSR_RQM;
-            if (direction != FD_DIR_VERIFY) {
-                /* Now, we just have to wait for the DMA controller to
-                 * recall us...
-                 */
-                k->hold_DREQ(fdctrl->dma, fdctrl->dma_chann);
-                k->schedule(fdctrl->dma);
-            } else {
-                /* Start transfer */
-                fdctrl_transfer_handler(fdctrl, fdctrl->dma_chann, 0,
-                                        fdctrl->data_len);
-            }
-            return;
+
+        /* No access is allowed until DMA transfer has completed */
+        fdctrl->msr &= ~FD_MSR_RQM;
+        if (direction != FD_DIR_VERIFY) {
+            /*
+             * Now, we just have to wait for the DMA controller to
+             * recall us...
+             */
+            k->hold_DREQ(fdctrl->dma, fdctrl->dma_chann);
+            k->schedule(fdctrl->dma);
         } else {
-            FLOPPY_DPRINTF("bad dma_mode=%d direction=%d\n", dma_mode,
-                           direction);
+            /* Start transfer */
+            fdctrl_transfer_handler(fdctrl, fdctrl->dma_chann, 0,
+                    fdctrl->data_len);
         }
+        return;
     }
     FLOPPY_DPRINTF("start non-DMA transfer\n");
     fdctrl->msr |= FD_MSR_NONDMA | FD_MSR_RQM;
diff --git a/hw/dma/i8257.c b/hw/dma/i8257.c
index 792f617eb4..85dad3d391 100644
--- a/hw/dma/i8257.c
+++ b/hw/dma/i8257.c
@@ -292,12 +292,6 @@ static uint64_t i8257_read_cont(void *opaque, hwaddr nport, unsigned size)
     return val;
 }
 
-static IsaDmaTransferMode i8257_dma_get_transfer_mode(IsaDma *obj, int nchan)
-{
-    I8257State *d = I8257(obj);
-    return (d->regs[nchan & 3].mode >> 2) & 3;
-}
-
 static bool i8257_dma_has_autoinitialization(IsaDma *obj, int nchan)
 {
     I8257State *d = I8257(obj);
@@ -400,6 +394,11 @@ static void i8257_dma_register_channel(IsaDma *obj, int nchan,
     r->opaque = opaque;
 }
 
+static bool i8257_is_verify_transfer(I8257Regs *r)
+{
+    return (r->mode & 0x0c) == 0;
+}
+
 static int i8257_dma_read_memory(IsaDma *obj, int nchan, void *buf, int pos,
                                  int len)
 {
@@ -407,6 +406,10 @@ static int i8257_dma_read_memory(IsaDma *obj, int nchan, void *buf, int pos,
     I8257Regs *r = &d->regs[nchan & 3];
     hwaddr addr = ((r->pageh & 0x7f) << 24) | (r->page << 16) | r->now[ADDR];
 
+    if (i8257_is_verify_transfer(r)) {
+        return len;
+    }
+
     if (r->mode & 0x20) {
         int i;
         uint8_t *p = buf;
@@ -431,6 +434,10 @@ static int i8257_dma_write_memory(IsaDma *obj, int nchan, void *buf, int pos,
     I8257Regs *r = &s->regs[nchan & 3];
     hwaddr addr = ((r->pageh & 0x7f) << 24) | (r->page << 16) | r->now[ADDR];
 
+    if (i8257_is_verify_transfer(r)) {
+        return len;
+    }
+
     if (r->mode & 0x20) {
         int i;
         uint8_t *p = buf;
@@ -597,7 +604,6 @@ static void i8257_class_init(ObjectClass *klass, void *data)
     dc->vmsd = &vmstate_i8257;
     dc->props = i8257_properties;
 
-    idc->get_transfer_mode = i8257_dma_get_transfer_mode;
     idc->has_autoinitialization = i8257_dma_has_autoinitialization;
     idc->read_memory = i8257_dma_read_memory;
     idc->write_memory = i8257_dma_write_memory;
diff --git a/include/hw/isa/isa.h b/include/hw/isa/isa.h
index 018ada4f6f..f516e253c5 100644
--- a/include/hw/isa/isa.h
+++ b/include/hw/isa/isa.h
@@ -56,7 +56,6 @@ typedef int (*IsaDmaTransferHandler)(void *opaque, int nchan, int pos,
 typedef struct IsaDmaClass {
     InterfaceClass parent;
 
-    IsaDmaTransferMode (*get_transfer_mode)(IsaDma *obj, int nchan);
     bool (*has_autoinitialization)(IsaDma *obj, int nchan);
     int (*read_memory)(IsaDma *obj, int nchan, void *buf, int pos, int len);
     int (*write_memory)(IsaDma *obj, int nchan, void *buf, int pos, int len);
-- 
2.23.0