pata_ali: disable ATAPI DMA

ATAPI DMA just doesn't work reliably on pata_ali.  The IDE driver can
do it but for some mysterious reason, pata_ali can't.  This patch
disables it by default and makes the driver whine during
initialization.  "pata_ali.atapi_dma" parameter is added so that user
can bypass the workaround.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/drivers/ata/pata_ali.c b/drivers/ata/pata_ali.c
index 8786455c901d..ce830fe3a362 100644
--- a/drivers/ata/pata_ali.c
+++ b/drivers/ata/pata_ali.c
@@ -36,6 +36,10 @@
 #define DRV_NAME "pata_ali"
 #define DRV_VERSION "0.7.5"
 
+int ali_atapi_dma = 0;
+module_param_named(atapi_dma, ali_atapi_dma, int, 0644);
+MODULE_PARM_DESC(atapi_dma, "Enable ATAPI DMA (0=disable, 1=enable)");
+
 /*
  *      Cable special cases
  */
@@ -270,6 +274,27 @@ static void ali_set_dmamode(struct ata_port *ap, struct ata_device *adev)
 }
 
 /**
+ *      ali_warn_atapi_dma      -       Warn about ATAPI DMA disablement
+ *      @adev: Device
+ *
+ *      Whine about ATAPI DMA disablement if @adev is an ATAPI device.
+ *      Can be used as ->dev_config.
+ */
+
+static void ali_warn_atapi_dma(struct ata_device *adev)
+{
+        struct ata_eh_context *ehc = &adev->link->eh_context;
+        int print_info = ehc->i.flags & ATA_EHI_PRINTINFO;
+
+        if (print_info && adev->class == ATA_DEV_ATAPI && !ali_atapi_dma) {
+                ata_dev_printk(adev, KERN_WARNING,
+                               "WARNING: ATAPI DMA disabled for reliablity issues.  It can be enabled\n");
+                ata_dev_printk(adev, KERN_WARNING,
+                               "WARNING: via pata_ali.atapi_dma modparam or corresponding sysfs node.\n");
+        }
+}
+
+/**
  *      ali_lock_sectors        -       Keep older devices to 255 sector mode
  *      @adev: Device
  *
@@ -283,6 +308,7 @@ static void ali_set_dmamode(struct ata_port *ap, struct ata_device *adev)
 static void ali_lock_sectors(struct ata_device *adev)
 {
         adev->max_sectors = 255;
+        ali_warn_atapi_dma(adev);
 }
 
 /**
@@ -294,6 +320,18 @@ static void ali_lock_sectors(struct ata_device *adev)
 
 static int ali_check_atapi_dma(struct ata_queued_cmd *qc)
 {
+        if (!ali_atapi_dma) {
+                /* FIXME: pata_ali can't do ATAPI DMA reliably but the
+                 * IDE alim15x3 driver can.  I tried lots of things
+                 * but couldn't find what the actual difference was.
+                 * If you got an idea, please write it to
+                 * linux-ide@vger.kernel.org and cc htejun@gmail.com.
+                 *
+                 * Disable ATAPI DMA for now.
+                 */
+                return -EOPNOTSUPP;
+        }
+
         /* If its not a media command, its not worth it */
         if (atapi_cmd_type(qc->cdb[0]) == ATAPI_MISC)
                 return -EOPNOTSUPP;
@@ -359,6 +397,7 @@ static struct ata_port_operations ali_20_port_ops = {
 
         .tf_load        = ata_tf_load,
         .tf_read        = ata_tf_read,
+        .check_atapi_dma = ali_check_atapi_dma,
         .check_status   = ata_check_status,
         .exec_command   = ata_exec_command,
         .dev_select     = ata_std_dev_select,
@@ -438,6 +477,7 @@ static struct ata_port_operations ali_c5_port_ops = {
         .check_status   = ata_check_status,
         .exec_command   = ata_exec_command,
         .dev_select     = ata_std_dev_select,
+        .dev_config     = ali_warn_atapi_dma,
 
         .freeze         = ata_bmdma_freeze,
         .thaw           = ata_bmdma_thaw,