Messages in this thread | | | From | John Keller <> | Subject | Re: [PATCH] ia64: SN specific version of dma_get_required_mask() | Date | Tue, 18 Nov 2008 08:08:11 -0600 (CST) |
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> > * John Keller [2008-11-17 10:24]: > > > > Create a platform specific version of dma_get_required_mask() > > for ia64 SN Altix. All SN Altix platforms support 64 bit DMA > > addressing regardless of the size of system memory. > > Create a ia64 machvec for dma_get_required_mask, with the > > SN version unconditionally returning DMA_64BIT_MASK. > > Maybe we should then switch the ia64_platform_is("sn2") > in check_crashkernel_memory() to dma_get_required_mask() == > DMA_64BIT_MASK because that's basically what the check is about. > > BTW: What about UV? > > > Regards, > Bernhard > -- > Bernhard Walle, SUSE Linux Products GmbH, Architecture Development >
This patch addresses a problem on SN Altix systems with < 4GB, where device drivers using the dma_get_required_mask() API would be told to use 32 bit DMA, when 64 bit is more efficient.
How exactly the use of dma_get_required_mask() relates to the crash kernel code you refer to is unclear to me.
If, for all platforms, the crash kernel code could use the mask returned from dma_get_required_mask() to do its check, then switching the code might be OK. But, if that's not possible for some platforms, then I'd wonder if dma_get_required_mask() is being used in the wrong context in this case.
For UV systems, the default/generic dma_get_required_mask() will be used, returning a value based on the size of system memory.
John
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