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authorDavid Flater <dave@flaterco.com>2013-05-10 16:37:43 +0400
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-05-22 02:21:02 +0400
commitbdf0eb3a026922dbf57f6839f3184c8d2ecc5f2e (patch)
tree1b51f2f6791f8ffe8b2b3ef4551f854513c9acbc /drivers/pnp
parentc7788792a5e7b0d5d7f96d0766b4cb6112d47d75 (diff)
downloadlinux-bdf0eb3a026922dbf57f6839f3184c8d2ecc5f2e.tar.xz
pnp: restore automatic resolution of DMA conflicts
To fix a 5-year-old regression, reverse changes made by commit 7ef3639 (PNP: don't fail device init if no DMA channel available). As an example to show the problem, my sound card provides a prioritized list of PnP "dependent sets" of requested resources: dependent set 0 (preferred) wants DMA 5. dependent set 1 (acceptable) will take DMA 5, 6, or 7. ... dependent set 4 (acceptable) doesn't request a high DMA. If DMA 5 is not available, pnp_assign_dma has to fail on set 0 so that pnp_auto_config_dev will move on to set 1 and get DMA 6 or 7. Instead, pnp_assign_dma adds the resource with flags |= IORESOURCE_DISABLED and returns success. pnp_auto_config_dev just sees success and therefore chooses set 0 with a disabled DMA and never tries the sets that would have resolved the conflict. Furthermore, this mode of "success" is unexpected and unhandled in sound/isa/sb and probably other drivers. sb assumes that the returned DMA is enabled and obliviously uses the invalid DMA number. Observed consequences were sb successfully grabbing a DMA that was expressly forbidden by the kernel parameter pnp_reserve_dma. The only upside to the original change would be as a kludge for devices that can operate in degraded mode without a DMA but that don't provide the corresponding non-preferred dependent set. The right workaround for those devices is to synthesize the missing set in quirks.c; otherwise, you're reinventing PnP fallback functionality at the driver level for that device and all others. Signed-off-by: David Flater <dave@flaterco.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/pnp')
-rw-r--r--drivers/pnp/manager.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/drivers/pnp/manager.c b/drivers/pnp/manager.c
index 95cebf0185de..9357aa779048 100644
--- a/drivers/pnp/manager.c
+++ b/drivers/pnp/manager.c
@@ -211,6 +211,12 @@ static int pnp_assign_dma(struct pnp_dev *dev, struct pnp_dma *rule, int idx)
res->start = -1;
res->end = -1;
+ if (!rule->map) {
+ res->flags |= IORESOURCE_DISABLED;
+ pnp_dbg(&dev->dev, " dma %d disabled\n", idx);
+ goto __add;
+ }
+
for (i = 0; i < 8; i++) {
if (rule->map & (1 << xtab[i])) {
res->start = res->end = xtab[i];
@@ -218,11 +224,9 @@ static int pnp_assign_dma(struct pnp_dev *dev, struct pnp_dma *rule, int idx)
goto __add;
}
}
-#ifdef MAX_DMA_CHANNELS
- res->start = res->end = MAX_DMA_CHANNELS;
-#endif
- res->flags |= IORESOURCE_DISABLED;
- pnp_dbg(&dev->dev, " disable dma %d\n", idx);
+
+ pnp_dbg(&dev->dev, " couldn't assign dma %d\n", idx);
+ return -EBUSY;
__add:
pnp_add_dma_resource(dev, res->start, res->flags);