On Monday 06 January 2014 05:39 PM, Russell King - ARM Linux wrote: > On Mon, Jan 06, 2014 at 08:28:20PM +0100, Krzysztof Hałasa wrote: >> Russell, Santosh, >> >> the unneeded commit causing regression is still in place. Please try to >> compile an ARM kernel without CONFIG_ARM_PATCH_PHYS_VIRT and with >> CONFIG_ZONE_DMA and see for yourself, if you don't believe me. >> >> Please be aware that this commit fixes nothing, its only function is >> causing the regression - so we don't lose anything by reverting it. >> >> If the attached wasn't clear, what the defective commit presently does >> is changing a perfectly valid code into a code referencing a variable >> which (without CONFIG_ARM_PATCH_PHYS_VIRT set) doesn't at all exist. >> >> With CONFIG_ARM_PATCH_PHYS_VIRT set, this commit does precisely nothing. > > Right, so, with Assabet, which has CONFIG_DMA_ZONE=y and > CONFIG_ARM_PATCH_PHYS_VIRT=y: > > $ make O=../build/assabet arch/arm/mm/init.i > > gives: > arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; > > with or without Santosh's patch. So, with V2P patching in place, there's > absolutely no functional difference. > > With CONFIG_ARM_PATCH_PHYS_VIRT=n, before Santosh's patch: > > arm_dma_limit = (0xc0000000UL) + arm_dma_zone_size - 1; > > After: > > arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1; > > and this breaks the build because there is no __pv_phys_offset symbol. > > Now, the case which matters for Santosh is the first case - the one > where CONFIG_ARM_PATCH_PHYS_VIRT=y. We can clearly see that after > preprocessing, the results are 100% identical. > > Therefore, I find myself agreeing with Krzysztof that the commit is > bad, has no functional change for the case it was proposed to solve, > and needs to be reverted. > May be I missed your point but I ended up creating the patch because the CMA reservation was failing on Keystone since the arm_dma_limit wasn't right since it wasn't considering the actual __pv_phys_offset.
Isn't that an issue ? Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
