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From: Nathan Whitehorn <nwhitehorn@FreeBSD.org>
Date: Tue, 28 Oct 2008 22:09:30 +0000 (UTC)
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Subject: svn commit: r184429 - head/sys/powerpc/powermac
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Author: nwhitehorn
Date: Tue Oct 28 22:09:30 2008
New Revision: 184429
URL: http://svn.freebsd.org/changeset/base/184429

Log:
  DBDMA can transfer a maximum of 64K - 1 bytes per descriptor, as the byte
  count field is 16 bits. Inform ATA of this fact.
  
  Reported by:	Marco Trillo

Modified:
  head/sys/powerpc/powermac/ata_dbdma.c

Modified: head/sys/powerpc/powermac/ata_dbdma.c
==============================================================================
--- head/sys/powerpc/powermac/ata_dbdma.c	Tue Oct 28 22:05:20 2008	(r184428)
+++ head/sys/powerpc/powermac/ata_dbdma.c	Tue Oct 28 22:09:30 2008	(r184429)
@@ -275,6 +275,12 @@ ata_dbdma_dmainit(device_t dev)
 	sc->sc_ch.dma.load = ata_dbdma_load;
 	sc->sc_ch.dma.reset = ata_dbdma_reset;
 
+	/*
+	 * DBDMA's field for transfer size is 16 bits. This will overflow
+	 * if we try to do a 64K transfer, so stop short of 64K.
+	 */
+	sc->sc_ch.dma.segsize = 126 * DEV_BSIZE;
+
 	sc->sc_ch.hw.status = ata_dbdma_status;
 
 	mtx_init(&sc->dbdma_mtx, "ATA DBDMA", NULL, MTX_DEF);