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author | David Flater <dave@flaterco.com> | 2013-05-10 14:37:43 +0200 |
---|---|---|
committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2013-05-22 00:21:02 +0200 |
commit | bdf0eb3a026922dbf57f6839f3184c8d2ecc5f2e (patch) | |
tree | 1b51f2f6791f8ffe8b2b3ef4551f854513c9acbc /drivers/pnp | |
parent | Linux 3.10-rc2 (diff) | |
download | linux-bdf0eb3a026922dbf57f6839f3184c8d2ecc5f2e.tar.xz linux-bdf0eb3a026922dbf57f6839f3184c8d2ecc5f2e.zip |
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.c | 14 |
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); |