[PATCH V2 2/8] dmaengine: bcm2835: remove unnecessary masking of dma channels
eric at anholt.net
Fri Jan 29 19:08:45 PST 2016
kernel at martin.sperl.org writes:
> From: Martin Sperl <kernel at martin.sperl.org>
> The original patch contained 3 dma channels that were masked out.
> These - as far as research and discussions show - are a
> artefacts remaining from the downstream legacy dma-api.
> Right now down-stream still includes a legacy api used only
> in a single (downstream only) driver (bcm2708_fb) that requires
> 2D DMA for speedup (DMA-channel 0).
> Formerly the sd-card support driver also was using this legacy
> api (DMA-channel 2), but since has been moved over to use
> dmaengine directly.
> The DMA-channel 3 is already masked out in the devicetree in
> the default property "brcm,dma-channel-mask = <0x7f35>;"
Delayed the rest of the review, because I went digging around in the
firmware, and missed the ifdef mess in it that produced 0x7f35. As far
as I can tell, though, we should be using just that value to control
which channels we expose (other than the shared-irq issue). If the
firmware wants to use a different set of channels some day, they'll have
to edit our DT.
Reviewed-by: Eric Anholt <eric at anholt.net>
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