Messages in this thread | | | Date | Thu, 02 Mar 2006 11:26:13 +0100 | From | Pierre Ossman <> | Subject | Re: How to map high memory for block io |
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Russell King wrote: > On Thu, Mar 02, 2006 at 10:52:04AM +0100, Pierre Ossman wrote: > >> Russell King wrote: >> >>> I think you're asking Jens that question - I know of no way to tell >>> the block layer that clustering is fine for normal but not highmem. >>> >> That wasn't what I meant. What I was referring to was disabling highmem >> altogether, the way that is done now through looking at the dma mask. >> > > You need to set your struct device's dma_mask appropriately: > > u64 limit = BLK_BOUNCE_HIGH; > > if (host->dev->dma_mask && *host->dev->dma_mask) > limit = *host->dev->dma_mask; > > blk_queue_bounce_limit(mq->queue, limit); > > Hence, if dma_mask is a NULL pointer or zero, highmem will be bounced. >
This I know. My beef is the readability of:
if (do_dma) *dev->dma_mask = DEVICE_DMA_MASK; else *dev->dma_mask = 0;
I.e. we use dma_mask even though we don't do DMA.
> Neither PNP nor your platform device sets dma_mask, so highmem will > always be bounced in the case of wbsd - which from what you write above > is what you require anyway. > >
wbsd isn't the issue, sdhci is. PCI sets a 32-bit mask by default so I end up with highmem pages even when I'm not doing DMA.
Rgds Pierre
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