[Qemu-devel] [PATCH] ATAPI CDROM DMA support is incomplete

[Juergen Keil]

Hi,


some time ago, ATAPI DMA support was added to hw/ide.c, but the DMA 
support is incomplete:  DMA data transfers are implemented
for ATAPI/SCSI READ commands only (GPCMD_READ_10, GPCMD_READ_12,
GPCMD_READ_CD), but all other ATAPI/SCSI commands still try to
transfer data using PIO mode.

Because of this problem, neither Windows ME nor Windows 2000 guests
will use ATAPI CD DMA transfers and fall back to PIO mode.

Or a OpenSolaris x86 guest will report errors like this
"WARNING: /address@hidden,0/address@hidden,1/address@hidden (ata1): timeout: 
abort request,
target=0 lun=0" and is unable to read data from the CD (You had to
force the ata/atapi driver to pio mode to work around this problem).


The attached patch adds DMA support for non-READ ATAPI/SCSI commands.

Index: hw/ide.c
===================================================================
RCS file: /cvsroot/qemu/qemu/hw/ide.c,v
retrieving revision 1.50
diff -u -B -r1.50 ide.c
--- hw/ide.c    5 Jan 2007 18:58:34 -0000       1.50
+++ hw/ide.c    19 Jan 2007 20:32:34 -0000
@@ -394,6 +394,7 @@
 } PCIIDEState;
 
 static void ide_dma_start(IDEState *s, BlockDriverCompletionFunc *dma_cb);
+static void ide_atapi_cmd_read_dma_cb(void *opaque, int ret);
 
 static void padstr(char *str, const char *src, int len)
 {
@@ -1063,11 +1064,17 @@
         size = max_size;
     s->lba = -1; /* no sector read */
     s->packet_transfer_size = size;
+    s->io_buffer_size = size;    /* dma: send the reply data as one chunk */
     s->elementary_transfer_size = 0;
     s->io_buffer_index = 0;
 
-    s->status = READY_STAT;
-    ide_atapi_cmd_reply_end(s);
+    if (s->atapi_dma) {
+       s->status = READY_STAT | DRQ_STAT;
+       ide_dma_start(s, ide_atapi_cmd_read_dma_cb);
+    } else {
+       s->status = READY_STAT;
+       ide_atapi_cmd_reply_end(s);
+    }
 }
 
 /* start a CD-CDROM read command */
@@ -1099,14 +1106,23 @@
     }
 
     if (s->io_buffer_size > 0) {
-        if (s->cd_sector_size == 2352) {
-            n = 1;
-            cd_data_to_raw(s->io_buffer, s->lba);
-        } else {
-            n = s->io_buffer_size >> 11;
-        }
+       /*
+        * For a cdrom read sector command (s->lba != -1),
+        * adjust the lba for the next s->io_buffer_size chunk
+        * and dma the current chunk.
+        * For a command != read (s->lba == -1), just transfer
+        * the reply data.
+        */
+       if (s->lba != -1) {
+           if (s->cd_sector_size == 2352) {
+               n = 1;
+               cd_data_to_raw(s->io_buffer, s->lba);
+           } else {
+               n = s->io_buffer_size >> 11;
+           }
+           s->lba += n;
+       }
         s->packet_transfer_size -= s->io_buffer_size;
-        s->lba += n;
         if (dma_buf_rw(bm, 1) == 0)
             goto eot;
     }
@@ -1170,7 +1186,8 @@
                                int sector_size)
 {
 #ifdef DEBUG_IDE_ATAPI
-    printf("read: LBA=%d nb_sectors=%d\n", lba, nb_sectors);
+    printf("read %s: LBA=%d nb_sectors=%d\n", s->atapi_dma ? "dma" : "pio",
+       lba, nb_sectors);
 #endif
     if (s->atapi_dma) {
         ide_atapi_cmd_read_dma(s, lba, nb_sectors, sector_size);