[src/trunk]: src/sys/dev/ata add a flag to start DMA before issuing commands ...

[macallan <macallan%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/561cf1732595
branches:  trunk
changeset: 323136:561cf1732595
user:      macallan <macallan%NetBSD.org@localhost>
date:      Fri Jun 01 18:13:30 2018 +0000

description:
add a flag to start DMA before issuing commands - needed to work around a bug
in some SATA chips which get confused if the disk responds too fast
Mostly for K2 SATA / svwsata found in G5 Macs
adapted from OpenBSD

diffstat:

 sys/dev/ata/ata_wdc.c |  15 ++++++++++-----
 sys/dev/ata/atavar.h  |   3 ++-
 2 files changed, 12 insertions(+), 6 deletions(-)

diffs (60 lines):

diff -r 9b0489deea7d -r 561cf1732595 sys/dev/ata/ata_wdc.c
--- a/sys/dev/ata/ata_wdc.c     Fri Jun 01 18:06:58 2018 +0000
+++ b/sys/dev/ata/ata_wdc.c     Fri Jun 01 18:13:30 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ata_wdc.c,v 1.109 2017/10/17 18:52:50 jdolecek Exp $   */
+/*     $NetBSD: ata_wdc.c,v 1.110 2018/06/01 18:13:30 macallan Exp $   */
 
 /*
  * Copyright (c) 1998, 2001, 2003 Manuel Bouyer.
@@ -54,7 +54,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ata_wdc.c,v 1.109 2017/10/17 18:52:50 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ata_wdc.c,v 1.110 2018/06/01 18:13:30 macallan Exp $");
 
 #include "opt_ata.h"
 #include "opt_wdc.h"
@@ -455,6 +455,10 @@
                        case WDCWAIT_THR:
                                return ATASTART_TH;
                        }
+                       /* start the DMA channel before */
+                       if ((chp->ch_flags & ATACH_DMA_BEFORE_CMD) != 0)
+                               (*wdc->dma_start)(wdc->dma_arg,
+                                   chp->ch_channel, xfer->c_drive);
                        if (ata_bio->flags & ATA_LBA48) {
                            uint8_t device = WDSD_LBA;
                            cmd = atacmd_to48(cmd);
@@ -468,9 +472,10 @@
                            wdccommand(chp, xfer->c_drive, cmd, cyl,
                                head, sect, count, features);
                        }
-                       /* start the DMA channel */
-                       (*wdc->dma_start)(wdc->dma_arg,
-                           chp->ch_channel, xfer->c_drive);
+                       /* start the DMA channel after */
+                       if ((chp->ch_flags & ATACH_DMA_BEFORE_CMD) == 0)
+                               (*wdc->dma_start)(wdc->dma_arg,
+                                   chp->ch_channel, xfer->c_drive);
                        chp->ch_flags |= ATACH_DMA_WAIT;
                        /* start timeout machinery */
                        if ((xfer->c_flags & C_POLL) == 0)
diff -r 9b0489deea7d -r 561cf1732595 sys/dev/ata/atavar.h
--- a/sys/dev/ata/atavar.h      Fri Jun 01 18:06:58 2018 +0000
+++ b/sys/dev/ata/atavar.h      Fri Jun 01 18:13:30 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: atavar.h,v 1.96 2018/04/16 22:33:28 jdolecek Exp $     */
+/*     $NetBSD: atavar.h,v 1.97 2018/06/01 18:13:30 macallan Exp $     */
 
 /*
  * Copyright (c) 1998, 2001 Manuel Bouyer.
@@ -407,6 +407,7 @@
 #define ATACH_TH_RESET 0x200   /* someone ask the thread to reset */
 #define ATACH_TH_RESCAN 0x400  /* rescan requested */
 #define ATACH_NCQ      0x800   /* channel executing NCQ commands */
+#define ATACH_DMA_BEFORE_CMD   0x1000  /* start DMA first */
 
        /* for the reset callback */
        int ch_reset_flags;